To improve the decorative properties, metal parts can be chrome-plated. The technology is widely used in the automotive industry and a number of other areas of the economy. Chrome plating of parts is also required to protect products from damage, improve their physical qualities. This method of metal processing has a number of other advantages and advantages.

The need for chrome

Metal chromium plating is understood as the process of plating with chromium to improve the surface properties and characteristics of elements. During chromium plating, diffuse saturation of various steel surfaces with chromium occurs. Chrome treatment is also acceptable for ABC plastic, aluminum, brass, silumin.

Chrome coating gives the appearance of parts a more beautiful look, ennobles them. The chrome layer provides the original metallic color, car alloy wheels, headlight reflectors, motorcycle parts, souvenirs or home furnishings begin to look more aesthetically pleasing.

Other advantages of chrome plating:

1. Protection. The application of a chromium layer helps to increase the resistance of products to temperature extremes, increases corrosion and erosion resistance, and reduces susceptibility to mechanical damage. Parts become superhard (950 - 1100 units on the corresponding scale), so they react less to chemical damage and do not oxidize.
2. Recovery. The service life of the base is greatly increased, large and small parts become very resistant to wear. With a low wear depth, chromium plating completely restores the product (for example, cracks up to 1 mm deep are closed at shafts and bushings).
3. reflective qualities. Some elements of the car are chrome-plated to increase visibility in the dark. Reflection improves the decorative qualities of the technique.
4. Purity. Chrome plating of products will protect them from dirt and dust, as it prevents the adhesion of various contaminants.

Compared to nickel plating, chromium plating has fewer disadvantages: the cost of services is lower, the coating will be harder and more durable. The use of nickel wins only in terms of decorative qualities, as the surface becomes even more aesthetic.

Scope of chrome plating

It is difficult to fully describe all the areas and areas where the technology is used. Chrome plating is indispensable in furniture industry, chrome handle accessories, finishing elements. The technique is popular in the production of plumbing - the element is applied to the external and inner surface pipes, bathtubs, sinks, used to cover handles, faucets.

In the automotive industry, the technology is used to manufacture:

• overlays and reflectors;
• aluminum rims;
• body elements;
• pistons;
• compression rings;
• rollers and axles.

Chrome plating is used in the production of rubber, plastics (chromium is applied to calender rolls and molds), and various measuring instruments. The material covers those elements that strongly rub against each other in order to increase their wear resistance.

Chrome plating technology

Exist different ways chrome plating, some can be used at home, with the appropriate equipment.

Galvanic chromium plating method

Galvanic chrome plating of parts is the most popular method, because all actions can be done by hand. Electroplating involves placing parts in a special solution with a certain composition, from where, under the influence of waves (solitons) of electric current, chromium atoms will be deposited on the surface. Having the right set of accessories for chrome plating, you can independently create a high-quality coating by.

Electrolytic chromium plating method

One of the varieties of electroplating. When using electrolysis, tri- or hexavalent chromium gives the product the desired "metal" look. When using a trivalent element, chromic anhydride acts as the main substance of the solution. The use of hexavalent chromium differs from the previous method by the presence of chromium sulfate in the solution.

When carrying out electrolytic chromium plating of discs or other parts, it is important to strictly observe the proportions of the components. Otherwise, the protective layer will quickly peel off or there will be spots on it, uneven haze and insufficient gloss.

Diffusion method of chromium plating

Chromium is sprayed using a galvanic brush. At home, this method is more preferable, because the master does not need to use a bath. It is especially recommended to perform the technique for parts made of aluminum, carbon steel, silicon alloys.

Chemical chromium plating

The use of chemical reagents helps to restore chromium from its salts. In the case of using chemistry, electric current is not required. Usually, phosphorus compounds, sodium citrate, acetic glacial acid, caustic soda 20% are taken as reagents.

Before applying the reagents, the parts are coated with a layer of copper. After finishing work, the workpieces are washed in water, dried, polished (initially, objects have a dull gray color).

Catalytic chromium plating method

Subspecies chemical chromium plating ferrous or non-ferrous metals, involving the application of a liquid without acids in the composition to the part. The technology is safe for humans and helps to create original, unusual effects.

Catalytic chromium plating can be applied to ordinary and flexible products (with electrolysis, the latter is impossible, the coating will peel off).

Usually, silver is taken as a reagent in an alkaline solution of ammonia, and formalin or hydrazine is taken as a reducing agent. The use of silver makes the detail milky with a mirror surface.

Vacuum chromium plating

The technology belongs to chemical metallization and has another name - PVD process. Gives condensation of chromium vapor on the surface of the part after placing it in a special vacuum chamber. In this installation, under negative pressure, chromium is heated to the evaporation temperature, then settling like a mist on the product.

The calculation of pressure, chrome plating period will depend on the degree of wear of the part, the type of material. After vacuum chromium plating, the thickness of the metal layer is minimal, so the part is coated on top with a special spray paint or varnished.

Thermochemical chromium plating

Apply funds in powders, consisting of fireclay, ferrochromium. The technique is similar to that for chemical chromium plating, only the product will be heated during the process.

DIY chrome plating

In order to repair products with a result no worse than according to GOST, it is important to strictly follow the sequence of work, to prepare the necessary equipment.

Workplace preparation

To comply with safety measures, in order not to inhale harmful, toxic substances, it is necessary to make a detailed preparation of the room for chrome plating.

You should perform the following actions:

1. Provide good ventilation. If work is carried out in the garage, open the doors, create forced ventilation in other rooms.
2. Buy and use personal protective equipment - glasses, a respirator, rubber or latex gloves, an apron, overalls.
3. Prepare tight bags for the disposal of production waste, which can be very caustic, harmful.
4. Remove any organic matter from the room, as it deteriorates upon contact with vapors of chromium compounds.
5. Immediately before work, lubricate the nasal cavity with a mixture of petroleum jelly and lanolin 2: 1.

Premises, chrome plating tools

For galvanization, you need to prepare the following tools and fixtures:

1. Bath galvanic. It can be any glass, propylene, polyethylene container, an enameled basin is suitable, for chrome plating of small objects - ordinary glass jars. The selected container must be placed in a wooden box, which is insulated from the inside with fiberglass and a layer of mineral wool. The container needs a tight-fitting lid.
2. Electrolyte heating device. The best for this purpose is a ceramic heating element (tubular electric heater), which will not collapse from contact with chemicals. Any other suitable heater may be used.
3. Electrodes. During chromium plating, a lead plate, which is placed in a container, will serve as an anode, and a clamp holding the part will act as a cathode. When placed in a container, the part should not touch its edges.
4. Thermometer with values ​​up to +100 degrees Celsius.

Professionals use special equipment for chrome plating - baths, electrical installations, washing and drying, ventilation systems. Even when using “home analogues”, the same chemical processes will occur in the tank, so the result will be close to the industrial one.

Source of power

To apply chromium, you will need the right battery. A grounded source is suitable direct current, the voltage of which is regulated within 1.5 - 12 V, the maximum current is 20 A. To adjust the power, the source must be equipped with a rheostat.

Composition and method of preparation of electrolytes

To precipitate chromium, you will need to boil and cool water or buy distilled water. For each liter of water, take 250 g of chromic anhydride, 2 - 2.5 g of sulfuric acid. The specific gravity of the latter should be 1.84 g / cu. cm.

The method of preparing electrolyte for chromium plating is as follows:

1. Fill the container ½ full with water. The temperature of the liquid should be + 60 degrees.
2. Carefully pour in chromic anhydride, stir until dissolved.
3. Pour in water until the tub is full.
4. Add acid.
5. Withstand the electrolyte for 3.5 hours under the influence of the rated current, which will help equalize the density.

As a result, the color of the liquid should become dark brown. After it settles for 24 hours in a cool room, then it is used for its intended purpose.

Surface preparation

From thoroughness preparatory activities will depend on the life of the finished coating and its appearance. First, the part must be cleaned, washed, and any contaminants removed. For better cleaning, you can use fine-grained sandpaper or grinder. It is important that paint, varnish, rust are completely removed.

After cleaning, the part should be degreased. Take calcined water (50 g of calcined water is diluted in a liter of water), add 150 g of sodium hydroxide, 5 g of silicate glue. The amount of solution can be increased if necessary, while maintaining the proportions. All components are heated to +90 degrees, the part is kept in the product for 20 minutes. The time can be increased up to 1 hour if the product is heavily soiled.

Chrome plating

The chrome plating process is simple, proceeds according to the following steps:

1. Heat the ready, settled electrolyte to +52 degrees, then keep this temperature constantly.
2. In the container, where the anode and cathode are already installed, put the part, heat it up to the specified temperature.
3. Apply voltage, withstand the product for 20 - 60 minutes, depending on the shape, type of bends.
4. Take out the product, rinse with distilled water.
5. Dry the item for at least 3 hours, completely eliminating contamination, touching with hands.

Chrome plating plastic products carried out with more care. The vapors emitted are very toxic, therefore it is forbidden to metallize plastic in residential areas.

In the process, a galvanic brush with bristles 25 mm in diameter is used, which is wrapped with lead wire. The brush is attached to the end of the vessel in which the electrolyte is poured. A diode is fixed from the second end, a step-down transformer is used in the circuit. The plus of the transformer is directed to the anode of the diode, the bristle winding is connected to the cathode. The solution is evenly applied to the part, passing through each zone about 20 times. Then the product is dried for 3 hours.

Possible defects and their causes

Often, during metallization, there is such an effect as hydrogenation - the indicator of the hydrogen content in chromium-plated steel increases. Because of similar problem the strength and plasticity of the metal decrease due to changes in its crystal lattice. The causes of hydrogenation have become diverse, most often this is due to an increase in temperature during the galvanization process.

Other troubles that can happen when chrome products:

1. Irregularity in gloss. It happens at a high current strength, which is supplied to the anode. Completely gloss may be absent with a small or too large amount of chromic anhydride, excess volume of sulfuric acid.
2. Brown spots. If there are such defects on the part, the anhydride rate in the solution is greatly overestimated or there is not enough sulfuric acid.
3. The softness of the coating. The reason is the low current strength during galvanization or the decrease in water temperature.
4. Fast chrome peel. The reason is poor degreasing before work, lowering the temperature of the solution.
5. Craters on the surface of the product. It happens due to the retention of hydrogen bubbles, on oxidized, porous substrates.

An excellent result can be obtained only with strict adherence to technology. This will give desired effect saving a significant amount of money.

You can give the car a spectacular appearance with the help of tuning. But not all car owners decide to perform expensive airbrushing, which also remains on the surface of the body for a long time, or paint their vehicle in additional colors.

Therefore, chrome plating is so popular - coating some body parts (usually car wheels) with a special paint or chrome plating compound. You can give a mirror shine to the entire body of the car completely, it will attract the eyes of others. More recently, chrome painting was not very popular, and only one shade could be achieved.

Today, chrome plating technology has changed a lot and with its help you can give the car any shade that the car owner wishes. The chrome-plated car body, although it looks impressive, but in Everyday life move on such vehicle not very safe.

Solar glare from the surface can blind other participants traffic which in turn could lead to an accident. Therefore, motorists prefer to chrome only some body parts so that the car looks like an elegant design development.

Chrome care

They tend to reflect sunlight, but over time, during operation, this ability may be lost. To prevent this from happening, the chrome surface must be carefully looked after.

It is recommended to wash the car only with warm water using special detergents for the car, after which they are wiped with a soft, lint-free cloth. It is very important not to use rough material and not to rub too hard, as scratches can appear on the chrome surface.

When washing, you should try to avoid strong temperature changes (this can contribute to cracking of the chrome film).

Chrome-plated parts also need anti-corrosion protection, just like other parts of the car body. The operation of the car under the influence of aggressive road reagents on the body is very undesirable, since there is a risk of corrosion.

Protect chrome parts special formulations if rust has already appeared, repair of the damaged area will be required. It will be necessary to remove the center of rust and clean the surface, but if the chrome layer has not been damaged, you just need to polish the part. You can even do this at home.

Chrome painting

There are several ways of chromium plating, which differ in cost and technology of coating the part. Chrome application technology:

1. With film.
2. Catalytic chromium plating.
3. Electrolytic chromium plating.

Painting chrome parts is a very responsible process, so when performing work, you must strictly follow the instructions. Painting a part from a spray can will be less time consuming than other methods, but in terms of the degree of reflection of sunlight from the surface, a part painted with this method will be much inferior to chrome-plated material. In addition, a part coated with chromium will better resist corrosion and its service life will increase.

You can paste over the car body with a special film that will give the surface not only the color of chrome, but also other shades - golden, mother-of-pearl, blue green or platinum. Before coating the car with paint, you need to carry out some preparatory work and follow the technology in the future:

• Apply a black undercoat to the prepared surface of the part.
• Polish it up.
• Apply paint with pigments of the desired color.
• Polish dried paint to a shiny surface.
• Cover the part with a protective layer of varnish.

This is a budget option chrome plating and it can be done even by a beginner. The film that gives the body parts the effect of chrome can be easily removed and there will be no visible marks left on the surface of the body. Such a film will additionally protect the paintwork of the car from negative factors. environment and possible scratches.

The method of catalytic and electrolytic chromium plating is considered more complex and expensive. It is necessary to perform work only in a specially equipped room and with the help of special equipment. In addition, the master must also have sufficient practical skills to correctly apply chrome to the surface of the body or part.

Catalytic chromium plating allows you to get a shiny mirror surface of any shade and at the same time all the materials used in the work are absolutely safe for human health.

Restoration of a chrome body part

In order for the surface to retain its mirror shine longer, it must be washed and polished regularly. For polishing chrome, you can purchase products that are sold in specialized automotive stores.

If traces of rust appear on the surface, you will need to remove the part and clean it. Depending on the degree and depth of damage, the coating is removed. You can do this with a grinder or coarse sandpaper.

Then the surface is additionally puttied and primed. After the layers of material have completely dried, it can be sanded and stained. As an alternative, you can cover the part with a metal film or try to do chrome plating at home.

For shallow damage to chrome, you can use GOI paste or a special polish, you need to work very carefully and use only soft cloths.

Do-it-yourself galvanic chrome plating of a part

To work, you need bristles from a dense brush, which must be wrapped with lead wire. Next, you need to make a brush, for this you can use plexiglass or an identical material. The body must be empty (so that electrolyte can be poured into the hole), and bristles must be attached to the other end.

Additionally, you will need to purchase a small power transformer, you can use the power supply for a small receiver. Plus, from the transformer, you need to conduct it to the anode of the diode, and connect the cathode to the wire that wraps the bristles.

The minus is attached to the part to be chrome plated. Before starting all work, the part must be carefully prepared - clean and degrease. The quality of the coating will depend on how well this was done - the cleaner the prepared part is, the better the chrome will adhere to its coating.

Then electrolyte is poured into a homemade brush, and the brush must be moved evenly over the entire surface of the workpiece. It will be necessary to repeat the procedure several times to obtain a coating of the desired thickness. Upon completion of work, the part is washed with plain water and carefully polished to a shine.

Information for action
(technology tips)
Erlykin L.A. DIY 3-92

Before any of the home craftsmen did not get up the need to nickel or chrome this or that part. What do-it-yourselfer has not dreamed of installing a “failed” bushing with a hard, wear-resistant surface obtained by saturating it with boron in a critical node. But how to do at home what, as a rule, is carried out at specialized enterprises using the methods of chemical-thermal and electrochemical processing metals. You will not build gas and vacuum furnaces at home, or build electrolysis baths. But it turns out that it is not necessary to build all this at all. It is enough to have on hand some reagents, an enamel pan and, perhaps, blowtorch, as well as know the recipes of "chemical technology", with the help of which metals can also be copper-plated, cadmium, tinned, oxidized, etc.

So, let's start getting acquainted with the secrets of chemical technology. Please note that the content of the components in the solutions given, as a rule, are given in g / l. If other units are used, a special clause follows.

Preparatory operations

Before applying paints, protective and decorative films to metal surfaces, as well as before coating them with other metals, it is necessary to carry out preparatory operations, that is, to remove pollution of various nature from these surfaces. Please note that the final result of all work depends to a large extent on the quality of the preparatory operations.

Preparatory operations include degreasing, cleaning and pickling.

Degreasing

The process of degreasing the surface of metal parts is carried out, as a rule, when these parts have just been processed (ground or polished) and there are no rust, scale and other foreign products on their surface.

With the help of degreasing, oil and grease films are removed from the surface of the parts. For this, aqueous solutions of some chemicals are used, although organic solvents can also be used for this. The latter have the advantage that they do not have a subsequent corrosive effect on the surface of the parts, but they are toxic and flammable.

aqueous solutions. Degreasing of metal parts in aqueous solutions is carried out in enameled dishes. Pour water, dissolve chemicals in it and put on a small fire. When the desired temperature is reached, the parts are loaded into the solution. During processing, the solution is stirred. Below are the compositions of the degreasing solutions (g/l), as well as the operating temperatures of the solutions and the processing time of the parts.

Compositions of degreasing solutions (g/l)

For ferrous metals (iron and iron alloys)

Liquid glass (stationery silicate glue) - 3 ... 10, caustic soda (potassium) - 20 ... 30, trisodium phosphate - 25 ... 30. Solution temperature - 70...90°C, processing time - 10...30 min.

Liquid glass - 5...10, caustic soda - 100...150, soda ash- 30...60. Solution temperature - 70...80°C, processing time - 5...10 min.

Liquid glass - 35, trisodium phosphate - 3 ... 10. Solution temperature - 70...90°С, processing time - 10...20 min.

Liquid glass - 35, trisodium phosphate - 15, preparation - emulsifier OP-7 (or OP-10) -2. Solution temperature - 60-70°С, processing time - 5...10 min.

Liquid glass - 15, preparation OP-7 (or OP-10) -1. Solution temperature - 70...80°С, processing time - 10...15 min.

Soda ash - 20, potassium chromium peak - 1. Solution temperature - 80 ... 90 ° C, processing time - 10 ... 20 minutes.

Soda ash - 5 ... 10, trisodium phosphate - 5 ... 10, preparation OP-7 (or OP-10) - 3. Solution temperature - 60 ... 80 ° C, processing time - 5 ... 10 min .

For copper and copper alloys

Caustic soda - 35, soda ash - 60, trisodium phosphate - 15, preparation OP-7 (or OP-10) - 5. Solution temperature - 60 ... 70, processing time - 10 ... 20 minutes.

Caustic soda (potassium) - 75, liquid glass- 20 Solution temperature - 80...90°С, processing time - 40...60 min.

Liquid glass - 10 ... 20, trisodium phosphate - 100. Solution temperature - 65 ... 80 C, processing time - 10 ... 60 minutes.

Liquid glass - 5 ... 10, soda ash - 20 ... 25, preparation OP-7 (or OP-10) - 5 ... 10. Solution temperature - 60...70°С, processing time - 5...10 min.

Trisodium phosphate - 80...100. Solution temperature - 80...90°С, processing time - 30...40 min.

For aluminum and its alloys

Liquid glass - 25...50, soda ash - 5...10, trisodium phosphate-5...10, preparation OP-7 (or OP-10) - 15...20 min.

Liquid glass - 20 ... 30, soda ash - 50 ... 60, trisodium phosphate - 50 ... 60. Solution temperature - 50…60°С, processing time - 3...5 min.

Soda ash - 20 ... 25, trisodium phosphate - 20 ... 25, preparation OP-7 (or OP-10) - 5 ... 7. Temperature - 70...80°С, processing time - 10...20 min.

For silver, nickel and their alloys

Liquid glass - 50, soda ash - 20, trisodium phosphate - 20, preparation OP-7 (or OP-10) - 2. Solution temperature - 70 ... 80 ° C, processing time - 5 ... 10 minutes.

Liquid glass - 25, soda ash - 5, trisodium phosphate - 10. Solution temperature - 75 ... 85 ° C, processing time - 15 ... 20 minutes.

For zinc

Liquid glass - 20 ... 25, caustic soda - 20 ... 25, soda ash - 20 ... 25. Solution temperature - 65...75°С, processing time - 5 min.

Liquid glass - 30...50, soda ash - 30..,50, kerosene - 30...50, preparation OP-7 (or OP-10) - 2...3. Solution temperature - 60-70°С, processing time - 1...2 min.

organic solvents

The most commonly used organic solvents are B-70 gasoline (or "lighter gasoline") and acetone. However, they have a significant drawback - they are easily ignited. Therefore, they have recently been replaced by non-flammable solvents such as trichlorethylene and perchlorethylene. Their dissolving power is much higher than that of gasoline and acetone. Moreover, these solvents can be fearlessly heated, which greatly accelerates the degreasing of metal parts.

Degreasing the surface of metal parts with organic solvents is carried out in the following sequence. The parts are loaded into a container with a solvent and incubated for 15 ... 20 minutes. Then the surface of the parts is wiped directly in the solvent with a brush. After such treatment, the surface of each part is carefully treated with a swab moistened with 25% ammonia (it is necessary to work with rubber gloves!).

All degreasing work organic solvents carried out in a well-ventilated area.

cleaning

In this section, as an example, the decarbonization process of internal combustion engines will be considered. As you know, carbon deposits are asphalt-resinous substances that form hard-to-remove films on the working surfaces of engines. Removing carbon deposits is a rather difficult task, since the carbon film is inert and firmly adhered to the surface of the part.

Compositions of cleaning solutions (g/l)

For ferrous metals

Liquid glass - 1.5, soda ash - 33, caustic soda - 25, laundry soap - 8.5. Solution temperature - 80...90°C, processing time - Zh.

Caustic soda - 100, potassium dichromate - 5. Solution temperature - 80 ... 95 ° C, processing time - up to 3 hours.

Caustic soda - 25, liquid glass - 10, sodium bichromate - 5, laundry soap- 8, soda ash - 30. Solution temperature - 80 ... 95 ° C, processing time - up to 3 hours.

Caustic soda - 25, liquid glass - 10, laundry soap - 10, potash - 30. Solution temperature - 100 ° C, processing time - up to 6 hours.

For aluminum (duralumin) alloys

Liquid glass 8.5, laundry soap - 10, soda ash - 18.5. Solution temperature - 85...95 C, processing time - up to 3 hours.

Liquid glass - 8, potassium dichromate - 5, laundry soap - 10, soda ash - 20. Solution temperature - 85 ... 95 ° C, processing time - up to 3 hours.

Soda ash - 10, potassium dichromate - 5, laundry soap - 10. Solution temperature - 80 ... 95 ° C, processing time - up to 3 hours.

Etching

Etching (as a preparatory operation) makes it possible to remove contaminants firmly adhered to their surface (rust, scale and other corrosion products) from metal parts.

The main purpose of etching is the removal of corrosion products; while the base metal should not be etched. To prevent metal etching, special additives are introduced into the solutions. Good results are obtained by the use of small amounts of hexamethylenetetramine (urotropine). In all solutions for etching ferrous metals, add 1 tablet (0.5 g) of urotropine per 1 liter of solution. In the absence of urotropin, it is replaced with the same amount of dry alcohol (sold in sports stores as fuel for tourists).

Due to the fact that recipes for etching use inorganic acids, you need to know their initial density (g / cm 3): nitric acid - 1.4, sulfuric acid - 1.84; hydrochloric acid - 1.19; phosphoric acid - 1.7; acetic acid - 1.05.

Compositions of solutions for etching

For ferrous metals

Sulfuric acid - 90...130, hydrochloric acid - 80...100. Solution temperature - 30...40°С, processing time - 0.5...1.0 h.

Sulfuric acid - 150...200. Solution temperature - 25...60°С, processing time - 0.5...1.0 h.

Hydrochloric acid - 200. Solution temperature - 30...35°С, processing time - 15...20 min.

Hydrochloric acid - 150 ... 200, formalin - 40 ... 50. Solution temperature 30...50°C, treatment time 15...25 min.

Nitric acid - 70...80, hydrochloric acid - 500...550. Solution temperature - 50°С, processing time - 3...5 min.

Nitric acid - 100, sulfuric acid - 50, hydrochloric acid - 150. Solution temperature - 85°C, processing time - 3...10 min.

Hydrochloric acid - 150, phosphoric acid - 100. Solution temperature - 50°C, processing time - 10...20 min.

The last solution (when processing steel parts), in addition to cleaning the surface, also phosphates it. And phosphate films on the surface of steel parts make it possible to paint them with any paint without a primer, since these films themselves serve as an excellent primer.

Here are a few more recipes for etching solutions, the compositions of which this time are given in% (by weight).

Orthophosphoric acid - 10, butyl alcohol - 83, water - 7. Solution temperature - 50...70°C, processing time - 20...30 min.

Orthophosphoric acid - 35, butyl alcohol - 5, water - 60. Solution temperature - 40...60°C, processing time - 30...35 min.

After etching of ferrous metals, they are washed in a 15% solution of soda ash (or drinking) soda. Then rinse thoroughly with water.

Note that below the compositions of the solutions are again given in g/L.

For copper and its alloys

Sulfuric acid - 25...40, chromic anhydride - 150...200. Solution temperature - 25°С, processing time - 5...10 min.

Sulfuric acid - 150, potassium bichromate - 50. Solution temperature - 25.35°C, processing time - 5...15 min.

Trilon B-100. Solution temperature - 18...25°C, processing time - 5...10 min.

Chromic anhydride - 350, sodium chloride - 50. Solution temperature - 18...25°С, processing time - 5...15 min.

For aluminum and its alloys

Caustic soda -50...100. Solution temperature - 40...60°С, treatment time - 5...10 s.

Nitric acid - 35...40. Solution temperature - 18...25°С, treatment time - 3...5 s.

Caustic soda - 25 ... 35, soda ash - 20 ... 30. Solution temperature - 40...60°С, treatment time - 0.5...2.0 min.

Caustic soda - 150, sodium chloride - 30. Solution temperature - 60°C, processing time - 15 ... 20 s.

Chemical polishing

Chemical polishing allows you to quickly and efficiently process the surface of metal parts. The great advantage of this technology is that with the help of it (and only it!) It is possible to polish parts with a complex profile at home.

Compositions of solutions for chemical polishing

For carbon steels (the content of components is indicated in each case in certain units (g / l, percent, parts)

Nitric acid - 2.-.4, hydrochloric acid 2 ... 5, Orthophosphoric acid - 15 ... 25, the rest is water. Solution temperature - 70...80°С, processing time - 1...10 min. The content of the components - in% (by volume).

Sulfuric acid - 0.1, acetic acid - 25, hydrogen peroxide (30%) - 13. Solution temperature - 18 ... 25 ° C, processing time - 30 ... 60 minutes. Content of components - in g/l.

Nitric acid - 100...200, sulfuric acid - 200..,600, hydrochloric acid - 25, Orthophosphoric acid - 400. Mixture temperature - 80...120°С, treatment time - 10...60 s. Content of components in parts (by volume).

For stainless steel

Sulfuric acid - 230, hydrochloric acid - 660, acid orange dye - 25. Solution temperature - 70...75°С, processing time - 2...3 min. Content of components - in g/l.

Nitric acid - 4 ... 5, hydrochloric acid - 3 ... 4, Orthophosphoric acid - 20..30, methyl orange - 1..1.5, the rest is water. Solution temperature - 18...25°С, treatment time - 5..10 min. The content of the components - in% (by weight).

Nitric acid - 30...90, potassium ferricyanide (yellow blood salt) - 2...15 g/l, preparation OP-7 - 3...25, hydrochloric acid - 45..110, phosphoric acid - 45. ..280.

Solution temperature - 30...40°С, processing time - 15...30 min. The content of components (except for yellow blood salt) - in pl / l.

The latter composition is applicable for polishing cast iron and any steels.

For copper

Nitric acid - 900, sodium chloride - 5, soot - 5. Solution temperature - 18 ... 25 ° C, processing time - 15 ... 20 s. Content of components - g/l.

Attention! Sodium chloride is added to solutions last, and the solution must be pre-cooled!

Nitric acid - 20, sulfuric acid - 80, hydrochloric acid - 1, chromic anhydride - 50. Solution temperature - 13..18°C, processing time - 1...2 min. Content of components - in ml.

Nitric acid 500, sulfuric acid - 250, sodium chloride - 10. Solution temperature - 18 ... 25 ° C, processing time - 10 ... 20 s. Content of components - in g/l.

For brass

Nitric acid - 20, hydrochloric acid - 0.01, acetic acid - 40, phosphoric acid - 40. Mixture temperature - 25...30°C, processing time - 20...60 s. Content of components - in ml.

Copper sulphate (copper sulfate) - 8, sodium chloride - 16, acetic acid - 3, water - the rest. Solution temperature - 20°С, processing time - 20...60 min. The content of components - in% (by weight).

For bronze

Orthophosphoric acid - 77 ... 79, potassium nitrate - 21 ... 23. Mixture temperature - 18°C, processing time - 0.5-3 min. The content of components - in% (by weight).

Nitric acid - 65, sodium chloride - 1 g, acetic acid - 5, orthophosphoric acid - 30, water - 5. Solution temperature - 18 ... 25 ° C, processing time - 1 ... 5 s. The content of components (except sodium chloride) - in ml.

For nickel and its alloys (cupronickel and nickel silver)

Nitric acid - 20, acetic acid - 40, phosphoric acid - 40. Mixture temperature - 20°C, processing time - up to 2 minutes. The content of components - in% (by weight).

Nitric acid - 30, acetic acid (glacial) - 70. Mixture temperature - 70...80°С, treatment time - 2...3 s. The content of components - in% (by volume).

For aluminum and its alloys

Orthophosphoric acid - 75, sulfuric acid - 25. Mixture temperature - 100°C, processing time - 5...10 min. The content of components - in parts (by volume).

Orthophosphoric acid - 60, sulfuric acid - 200, nitric acid - 150, urea - 5g. The temperature of the mixture is 100°C, the processing time is 20 s. The content of components (except urea) - in ml.

Phosphoric acid - 70, sulfuric acid - 22, boric acid- 8. Mixture temperature - 95°C, processing time - 5...7 min. The content of components - in parts (by volume).

Passivation

Passivation is the process of chemically creating an inert layer on the surface of a metal, which prevents the metal itself from oxidizing. The process of passivating the surface of metal products is used by chasers when creating their works; craftsmen - in the manufacture of various crafts (chandeliers, sconces and other household items); sports anglers passivate their homemade metal lures.

Compositions of solutions for passivation (g/l)

For ferrous metals

Sodium nitrite - 40...100. Solution temperature - 30...40°С, processing time - 15...20 min.

Sodium nitrite - 10...15, soda ash - 3...7. Solution temperature - 70...80°С, processing time - 2...3 min.

Sodium nitrite - 2...3, soda ash - 10, preparation OP-7 - 1...2. Solution temperature - 40...60°С, processing time - 10...15 min.

Chromic anhydride - 50. Solution temperature - 65 ... 75 "C, processing time - 10 ... 20 minutes.

For copper and its alloys

Sulfuric acid - 15, potassium dichromate - 100. Solution temperature - 45°C, processing time - 5...10 min.

Potassium bichromate - 150. Solution temperature - 60°C, processing time - 2...5 min.

For aluminum and its alloys

Orthophosphoric acid - 300, chromic anhydride - 15. Solution temperature - 18...25°C, processing time - 2...5 min.

Potassium dichromate - 200. Solution temperature - 20°C, "treatment time -5...10 min.

For silver

Potassium dichromate - 50. Solution temperature - 25 ... 40 ° C, processing time - 20 minutes.

For zinc

Sulfuric acid - 2...3, chromic anhydride - 150...200. Solution temperature - 20°С, processing time - 5...10 s.

Phosphating

As already mentioned, the phosphate film on the surface of steel parts is a fairly reliable anti-corrosion coating. It is also an excellent primer for paintwork.

Some low-temperature phosphating methods are applicable to bodywork cars before coating them with anti-corrosion and anti-wear compounds.

Compositions of solutions for phosphating (g/l)

For steel

Mazhef (phosphate salts of manganese and iron) - 30, zinc nitrate - 40, sodium fluoride - 10. Solution temperature - 20 ° C, processing time - 40 minutes.

Monozinc phosphate - 75, zinc nitrate - 400 ... 600. Solution temperature - 20°С, processing time - 20...30 s.

Majef - 25, zinc nitrate - 35, sodium nitrite - 3. Solution temperature - 20°C, processing time - 40 min.

Monoammonium phosphate - 300. Solution temperature - 60 ... 80 ° C, processing time - 20 ... 30 s.

Phosphoric acid - 60...80, chromic anhydride - 100...150. Solution temperature - 50...60°С, processing time - 20...30 min.

Orthophosphoric acid - 400 ... 550, butyl alcohol - 30. Solution temperature - 50 ° C, processing time - 20 minutes.

Application of metal coatings

The chemical coating of some metals with others impresses with the simplicity of the technological process. Indeed, if, for example, it is necessary to chemically nickel plate some steel part, it is enough to have suitable enameled dishes, a heating source ( gas stove, primus, etc.) and relatively non-deficient chemicals. An hour or two - and the part is covered with a shiny layer of nickel.

Note that only with the help of chemical nickel plating it is possible to reliably nickel-plating parts complex profile, internal cavities (pipes, etc.). True, chemical nickel plating (and some other similar processes) is not without its drawbacks. The main one is not too strong adhesion of the nickel film to the base metal. However, this drawback can be eliminated; for this, the so-called low-temperature diffusion method is used. It allows you to significantly increase the adhesion of the nickel film to the base metal. This method is applicable to all chemical coatings of some metals by others.

nickel plating

The process of chemical nickel plating is based on the reaction of nickel reduction from aqueous solutions its salts using sodium hypophosphite and some other chemicals.

Nickel coatings obtained by chemical means have an amorphous structure. The presence of phosphorus in nickel makes the film close in hardness to a chromium film. Unfortunately, the adhesion of the nickel film to the base metal is relatively low. Heat treatment of nickel films (low-temperature diffusion) consists in heating nickel-plated parts to a temperature of 400°C and holding them at this temperature for 1 hour.

If nickel-plated parts are hardened (springs, knives, fish hooks, etc.), then at a temperature of 40 ° C they can be released, that is, they can lose their main quality - hardness. In this case, low-temperature diffusion is carried out at a temperature of 270...300 C with an exposure of up to 3 hours. In this case, the heat treatment also increases the hardness of the nickel coating.

All the listed advantages of chemical nickel plating did not escape the attention of technologists. They found them practical use(except for the use of decorative and anti-corrosion properties). So, with the help of chemical nickel plating, the axes of various mechanisms, worms of thread-cutting machines, etc. are repaired.

At home, with the help of nickel plating (of course, chemical!) You can repair parts of various household devices. The technology here is extremely simple. For example, the axis of a device was demolished. Then they build up (with excess) a layer of nickel on the damaged area. Then the working section of the axis is polished, bringing it to the desired size.

It should be noted that chemical nickel plating cannot cover metals such as tin, lead, cadmium, zinc, bismuth and antimony.
Solutions used for chemical nickel plating are divided into acidic (pH - 4 ... 6.5) and alkaline (pH - above 6.5). Acidic solutions are preferably used for coating ferrous metals, copper and brass. Alkaline - for stainless steels.

Acidic solutions (compared to alkaline ones) on a polished part give a smoother (mirror-like) surface, they have less porosity, and the speed of the process is higher. Another important feature of acidic solutions is that they are less likely to self-discharge when the operating temperature is exceeded. (Self-discharge - instantaneous precipitation of nickel into a solution with splashing of the latter.)

In alkaline solutions, the main advantage is a more reliable adhesion of the nickel film to the base metal.

And the last. Water for nickel plating (and when applying other coatings) is taken distilled (you can use condensate from household refrigerators). Chemical reagents are suitable at least pure (designation on the label - H).

Before coating parts with any metal film, it is necessary to conduct a special preparation of their surface.

Preparation of all metals and alloys is as follows. The treated part is degreased in one of the aqueous solutions, and then the part is decapitated in one of the solutions listed below.

Compositions of solutions for decapitation (g/l)

For steel

Sulfuric acid - 30...50. Solution temperature - 20°С, processing time - 20...60 s.

Hydrochloric acid - 20...45. Solution temperature - 20°С, treatment time - 15...40 s.

Sulfuric acid - 50...80, hydrochloric acid - 20...30. Solution temperature - 20°С, processing time - 8...10 s.

For copper and its alloys

Sulfuric acid - 5% solution. Temperature - 20°C, processing time - 20s.

For aluminum and its alloys

Nitric acid. (Attention, 10 ... 15% solution.) Solution temperature - 20 ° C, processing time - 5 ... 15 s.

Please note that for aluminum and its alloys before chemical nickel plating carry out another processing - the so-called zincate. Below are solutions for zincate treatment.

For aluminum

Caustic soda - 250, zinc oxide - 55. Solution temperature - 20 C, treatment time - 3 ... 5s.

Caustic soda - 120, zinc sulfate - 40. Solution temperature - 20 ° C, processing time - 1.5 ... 2 minutes.

When preparing both solutions, first, caustic soda is dissolved separately in half of the water, and the zinc component in the other half. Then both solutions are poured together.

For cast aluminum alloys

Caustic soda - 10, zinc oxide - 5, Rochelle salt (crystal hydrate) - 10. Solution temperature - 20 C, processing time - 2 minutes.

For wrought aluminum alloys

Ferric chloride (crystal hydrate) - 1, sodium hydroxide - 525, zinc oxide 100, Rochelle salt - 10. Solution temperature - 25 ° C, processing time - 30 ... 60 s.

After zincate treatment, the parts are washed in water and hung in a nickel plating solution.

All solutions for nickel plating are universal, that is, they are suitable for all metals (although there are some specifics). Prepare them in a certain sequence. So, all chemicals (except sodium hypophosphite) are dissolved in water (enamelled dishes!). Then the solution is heated to the operating temperature and only after that sodium hypophosphite is dissolved and the parts are hung into the solution.

In 1 liter of solution, a surface up to 2 dm2 in area can be nickel plated.

Compositions of solutions for nickel plating (g/l)

Nickel sulphate - 25, sodium succinic acid - 15, sodium hypophosphite - 30. Solution temperature - 90°C, pH - 4.5, film growth rate - 15...20 µm/h.

Nickel chloride - 25, sodium succinic acid - 15, sodium hypophosphite - 30. Solution temperature - 90 ... 92 ° C, pH - 5.5, growth rate - 18 ... 25 μm / h.

Nickel chloride - 30, glycolic acid - 39, sodium hypophosphite - 10. Solution temperature 85..89°С, pH - 4.2, growth rate - 15...20 µm/h.

Nickel chloride - 21, sodium acetate - 10, sodium hypophosphite - 24, Solution temperature - 97 ° C, pH - 5.2, growth rate - up to 60 μm / h.

Nickel sulfate - 21, sodium acetate - 10, lead sulfide - 20, sodium hypophosphite - 24. Solution temperature - 90 ° C, pH - 5, growth rate - up to 90 μm / h.

Nickel chloride - 30, acetic acid - 15, lead sulfide - 10 ... 15, sodium hypophosphite - 15. Solution temperature - 85 ... 87 ° C, pH - 4.5, growth rate - 12 ... 15 microns /h

Nickel chloride - 45, ammonium chloride - 45, sodium citrate - 45, sodium hypophosphite - 20. Solution temperature - 90 ° C, pH - 8.5, growth rate - 18 ... 20 microns / h.

Nickel chloride - 30, ammonium chloride - 30, sodium succinic acid - 100, ammonia (25% solution - 35, sodium hypophosphite - 25).
Temperature - 90°C, pH - 8...8.5, growth rate - 8...12 µm/h.

Nickel chloride - 45, ammonium chloride - 45, sodium acetate - 45, sodium hypophosphite - 20. Solution temperature - 88 .... 90 ° C, pH - 8 ... 9, growth rate - 18 ... 20 microns / h.

Nickel sulphate - 30, ammonium sulphate - 30, sodium hypophosphite - 10. Solution temperature - 85°C, pH - 8.2...8.5, growth rate - 15...18 µm/h.

Attention! According to existing state standards, a single-layer nickel coating per 1 cm2 has several tens of through (to the base metal) pores. Naturally, in the open air, a nickel-plated steel part will quickly become covered with a “rash” of rust.

In a modern car, for example, the bumper is covered with a double layer (a sublayer of copper, and chrome on top) and even a triple layer (copper - nickel - chrome). But even this does not save the part from rust, since according to GOST and the triple coating has several pores per 1 cm2. What to do? The way out is in the surface treatment of the coating with special compounds that close the pores.

Wipe the part with a nickel (or other) coating with a slurry of magnesium oxide and water and immediately lower it for 1 ... 2 minutes in a 50% hydrochloric acid solution.

After heat treatment, lower the part that has not yet cooled down into non-vitaminized fish oil (preferably old, unsuitable for its intended purpose).

Wipe the nickel-plated surface of the part 2...3 times with the composition of LPS (easy penetrating lubricant).

In the last two cases, excess fat (grease) is removed from the surface with gasoline in a day.

The treatment of large surfaces (bumpers, car moldings) with fish oil is carried out as follows. In hot weather, wipe them with fish oil twice with a break of 12-14 hours. Then, after 2 days, excess fat is removed with gasoline.

The effectiveness of such processing is characterized by the following example. Nickel-plated fishing hooks begin to rust immediately after the first sea fishing. The same hooks treated with fish oil do not corrode for almost the entire summer sea fishing season.

Chrome plating

Chemical chromium plating allows you to get a coating on the surface of metal parts gray color, which after polishing acquires the desired shine. Chrome adheres well to nickel plating. The presence of phosphorus in chemically produced chromium greatly increases its hardness. Heat treatment for chrome plating is necessary.

Below are proven recipes for chemical chromium plating.

Compositions of solutions for chemical chromium plating (g/l)

Chromium fluoride - 14, sodium citrate - 7, acetic acid - 10 ml, sodium hypophosphite - 7. Solution temperature - 85 ... 90 ° C, pH - 8 ... 11, growth rate - 1.0 ... 2 .5 µm/h.

Chromium fluoride - 16, chromium chloride - 1, sodium acetate - 10, sodium oxalate - 4.5, sodium hypophosphite - 10. Solution temperature - 75 ... 90 ° C, pH - 4 ... 6, growth rate - 2 ...2.5 µm/h.

Chromium fluoride - 17, chromium chloride - 1.2, sodium citrate - 8.5, sodium hypophosphite - 8.5. Solution temperature - 85...90°C, pH - 8...11, growth rate - 1...2.5 µm/h.

Chromium acetate - 30, nickel acetate - 1, sodium glycolate - 40, sodium acetate - 20, sodium citrate - 40, acetic acid - 14 ml, sodium hydroxide - 14, sodium hypophosphite - 15. Solution temperature - 99 ° C, pH - 4...6, growth rate - up to 2.5 µm/h.

Chromium fluoride - 5 ... 10, chromium chloride - 5 ... 10, sodium citrate - 20 ... 30, sodium pyrophosphate (replacing sodium hypophosphite) - 50 ... 75.
Solution temperature - 100°C, pH - 7.5...9, growth rate - 2...2.5 µm/h.

Boronickel plating

The film of this dual alloy has increased hardness (especially after heat treatment), high melting point, high wear resistance and significant corrosion resistance. All this allows the use of such a coating in various responsible home-made structures. Below are the recipes for solutions in which boronickeling is carried out.

Compositions of solutions for chemical boron nickel plating (g/l)

Nickel chloride - 20, sodium hydroxide - 40, ammonia (25% solution): - 11, sodium borohydride - 0.7, ethylenediamine (98% solution) - 4.5. Solution temperature - 97°C, growth rate - 10 µm/h.

Nickel sulfate - 30, triethylsyntetramine - 0.9, sodium hydroxide - 40, ammonia (25% solution) - 13, sodium borohydride - 1. Solution temperature - 97 C, growth rate - 2.5 μm / h.

Nickel chloride - 20, sodium hydroxide - 40, Rochelle salt - 65, ammonia (25% solution) - 13, sodium borohydride - 0.7. Solution temperature - 97°C, growth rate - 1.5 µm/h.

Caustic soda - 4 ... 40, potassium metabisulphite - 1 ... 1.5, potassium sodium tartrate - 30 ... 35, nickel chloride - 10 ... 30, ethylenediamine (50% solution) - 10 ... 30 , sodium borohydride - 0.6 ... 1.2. Solution temperature - 40...60°C, growth rate - up to 30 µm/h.

Solutions are prepared in the same way as for nickel plating: first, everything except sodium borohydride is dissolved, the solution is heated and sodium borohydride is dissolved.

Borocobalting

The use of this chemical process makes it possible to obtain a film of particularly high hardness. It is used to repair friction pairs, where increased wear resistance of the coating is required.

Compositions of solutions for boron cobalt treatment (g/l)

Cobalt chloride - 20, sodium hydroxide - 40, sodium citrate - 100, ethylenediamine - 60, ammonium chloride - 10, sodium borohydride - 1. Solution temperature - 60 ° C, pH - 14, growth rate - 1.5 .. .2.5 µm/h.

Cobalt acetate - 19, ammonia (25% solution) - 250, potassium tartrate - 56, sodium borohydride - 8.3. Solution temperature - 50°С, pH - 12.5, growth rate - 3 µm/h.

Cobalt sulphate - 180, boric acid - 25, dimethylborazan - 37. Solution temperature - 18°C, pH - 4, growth rate - 6 µm/h.

Cobalt chloride - 24, ethylenediamine - 24, dimethylborazan - 3.5. Solution temperature - 70 C, pH - 11, growth rate - 1 µm/h.

The solution is prepared in the same way as boronickel.

Cadmium plating

On the farm, it is often necessary to use fasteners coated with cadmium. This is especially true for parts that are operated outdoors.

It is noted that chemically obtained cadmium coatings adhere well to the base metal even without heat treatment.

Cadmium chloride - 50, ethylenediamine - 100. Cadmium should be in contact with parts (suspension on cadmium wire, small parts are sprinkled with cadmium powder). Solution temperature - 65°C, pH - 6...9, growth rate - 4 µm/h.

Attention! Ethylenediamine is dissolved last in the solution (after heating).

copper plating

Chemical copper plating is most often used in the manufacture of printed circuit boards for radio electronics, in electroforming, for metallization of plastics, for double coating of some metals with others.

Compositions of solutions for copper plating (g/l)

Copper sulphate - 10, sulfuric acid - 10. Solution temperature - 15...25°C, growth rate - 10 µm/h.

Potassium-sodium tartrate - 150, copper sulphate - 30, caustic soda - 80. Solution temperature - 15 ... 25 ° C, growth rate - 12 μm / h.

Copper sulphate - 10 ... 50, caustic soda - 10 ... 30, Rochelle salt 40 ... 70, formalin (40% solution) - 15 ... 25. Solution temperature - 20°C, growth rate - 10 µm/h.

Sulfuric copper - 8...50, sulfuric acid - 8...50. Solution temperature - 20°C, growth rate - 8 µm/h.

Copper sulphate - 63, potassium tartrate - 115, sodium carbonate - 143. Solution temperature - 20 C, growth rate - 15 µm/h.

Copper sulphate - 80 ... 100, caustic soda - 80 ..., 100, sodium carbonate - 25 ... 30, nickel chloride - 2 ... 4, Rochelle salt - 150 ... 180, formalin (40% - solution) - 30...35. Solution temperature - 20°C, growth rate - 10 µm/h. This solution makes it possible to obtain films with a low nickel content.

Copper sulfate - 25 ... 35, sodium hydroxide - 30 ... 40, sodium carbonate - 20-30, trilon B - 80 ... 90, formalin (40% solution) - 20 ... 25, rhodanine - 0.003 ... 0.005, potassium ferricyanide (red blood salt) - 0.1..0.15. Solution temperature - 18...25°C, growth rate - 8 µm/h.

This solution is highly stable over time and makes it possible to obtain thick copper films.

To improve the adhesion of the film to the base metal, heat treatment is the same as for nickel.

Silvering

Silver plating of metal surfaces is perhaps the most popular process among craftsmen, which they use in their work. Dozens of examples could be given. For example, restoration of the silver layer on cupronickel cutlery, silvering of samovars and other household items.

For silver chasers together with chemical staining metal surfaces (it will be discussed below) - a way to increase the artistic value of chased paintings. Imagine a minted ancient warrior with silver plated chain mail and a helmet.

The process of chemical silvering can be carried out using solutions and pastes. The latter is preferable when processing large surfaces (for example, when silvering samovars or parts of large chased paintings).

Composition of solutions for silvering (g/l)

Silver chloride - 7.5, potassium ferricyanide - 120, potassium carbonate - 80. The temperature of the working solution is about 100 ° C. Processing time - until the desired thickness of the silver layer is obtained.

Silver chloride - 10, sodium chloride - 20, acid potassium tartrate - 20. Processing - in a boiling solution.

Silver chloride - 20, potassium ferricyanide - 100, potassium carbonate - 100, ammonia (30% solution) - 100, sodium chloride - 40. Processing - in a boiling solution.

First, a paste is prepared from silver chloride - 30 g, tartaric acid - 250 g, sodium chloride - 1250, and everything is diluted with water to the density of sour cream. 10 ... 15 g of paste is dissolved in 1 liter of boiling water. Processing - in a boiling solution.

Details are hung in solutions for silvering on zinc wires (strips).

The processing time is determined visually. It should be noted here that brass is better silvered than copper. On the latter it is necessary to apply a fairly thick layer of silver in order to dark copper would not shine through the coating layer.

One more note. Solutions with silver salts cannot be stored for a long time, as explosive components can be formed in this case. The same applies to all liquid pastes.

Compositions of pastes for silvering.

In 300 ml warm water dissolve 2 g of lapis pencil (sold in pharmacies, it is a mixture of silver nitrate and amino acid potassium, taken in a ratio of 1: 2 (by weight). A 10% sodium chloride solution is gradually added to the resulting solution until the precipitation stops. silver chloride is filtered off and thoroughly washed in 5-6 waters.

Dissolve 20 g of sodium thiosulfite in 100 ml of water. Silver chloride is added to the resulting solution until it no longer dissolves. The solution is filtered and tooth powder is added to it to the consistency of liquid sour cream. This paste is rubbed (silvered) with a cotton swab.

Lapis pencil - 15, citric acid (food) - 55, ammonium chloride - 30. Each component is ground into powder before mixing. The content of components - in% (by weight).

Silver chloride - 3, sodium chloride - 3, sodium carbonate - 6, chalk - 2. The content of components - in parts (by weight).

Silver chloride - 3, sodium chloride - 8, potassium tartrate - 8, chalk - 4. Content of components - in parts (by weight).

Silver nitrate - 1, sodium chloride - 2. Content of components - in parts (by weight).

The last four pastes are used as follows. Finely divided components are mixed. With a wet swab, powdering it with a dry mixture of chemicals, they rub (silver) the desired part. The mixture is added all the time, constantly moistening the swab.

When silvering aluminum and its alloys, the parts are first galvanized and then coated with silver.

Zincate treatment is carried out in one of the following solutions.

Compositions of solutions for zincate treatment (g/l)

For aluminum

Caustic soda - 250, zinc oxide - 55. Solution temperature - 20°C, treatment time - 3...5 s.

Caustic soda - 120, zinc sulfate - 40. Solution temperature - 20°C, processing time - 1.5...2.0 min. To obtain a solution, first caustic soda is dissolved in one half of the water, and zinc sulfate is dissolved in the other. Then both solutions are poured together.

For duralumin

Caustic soda - 10, zinc oxide - 5, Rochelle salt - 10. Solution temperature - 20°C, processing time - 1...2 min.

After zincate treatment, the parts are silvered in any of the above solutions. However, the following solutions (g / l) are considered the best.

Silver nitrate - 100, ammonium fluoride - 100. Solution temperature - 20°C.

Silver fluoride - 100, ammonium nitrate - 100. Solution temperature - 20°C.

Tinning

Chemical tinning of surfaces of parts is used as an anti-corrosion coating and as a preliminary process (for aluminum and its alloys) before soft soldering. Below are compositions for tinning some metals.

Compositions for tinning (g/l)

For steel

Stannous chloride (fused) - 1, ammonia alum - 15. Tinning is carried out in a boiling solution, the growth rate is 5 ... 8 microns / h.

Tin chloride - 10, aluminum-ammonium sulphate - 300. Tinning is carried out in a boiling solution, the growth rate is 5 microns / h.

Stannous chloride - 20, Rochelle salt - 10. Solution temperature - 80°C, growth rate - 3...5 µm/h.

Stannous chloride - 3 ... 4, Rochelle salt - until saturation. Solution temperature - 90...100°С, growth rate - 4...7 µm/h.

For copper and its alloys

Stannous chloride - 1, potassium tartrate - 10. Tinning is carried out in a boiling solution, the growth rate is 10 μm / h.

Stannous chloride - 20, sodium lactate - 200. Solution temperature - 20°C, growth rate - 10 µm/h.

Stannous chloride - 8, thiourea - 40...45, sulfuric acid - 30...40. Solution temperature - 20°C, growth rate - 15 µm/h.

Stannous chloride - 8...20, thiourea - 80...90, hydrochloric acid - 6.5...7.5, sodium chloride - 70...80. Solution temperature - 50...100°C, growth rate - 8 µm/h.

Stannous chloride - 5.5, thiourea - 50, tartaric acid - 35. Solution temperature - 60 ... 70 ° C, growth rate - 5 ... 7 μm / h.

When tinning parts made of copper and its alloys, they are hung on zinc pendants. Small parts are “powdered” with zinc filings.

For aluminum and its alloys

The tinning of aluminum and its alloys is preceded by some additional processes. First, the parts degreased with acetone or gasoline B-70 are treated for 5 minutes at a temperature of 70 ° C of the following composition (g / l): sodium carbonate - 56, sodium phosphate - 56. Then the parts are lowered for 30 s into a 50% solution of nitric acid, rinse thoroughly under running water and immediately place in one of the solutions (for tinning) below.

Sodium stannate - 30, sodium hydroxide - 20. Solution temperature - 50...60°C, growth rate - 4 µm/h.

Sodium stannate - 20 ... 80, potassium pyrophosphate - 30 ... 120, sodium hydroxide - 1.5..L, 7, ammonium oxalate - 10 ... 20. Solution temperature - 20...40°C, growth rate - 5 µm/h.

Removal of metal coatings

Usually this process is necessary to remove low-quality metal films or to clean any metal product being restored.

All of the following solutions work faster at elevated temperatures.

Compositions of solutions for removing metal coatings in parts (by volume)

For steel removing nickel from steel

Nitric acid - 2, sulfuric acid - 1, iron sulphate (oxide) - 5 ... 10. The temperature of the mixture is 20°C.

Nitric acid - 8, water - 2. Solution temperature - 20 C.

Nitric acid - 7, acetic acid (glacial) - 3. Mixture temperature - 30°C.

For removing nickel from copper and its alloys (g/l)

Nitrobenzoic acid - 40 ... 75, sulfuric acid - 180. Solution temperature - 80 ... 90 C.

Nitrobenzoic acid - 35, ethylenediamine - 65, thiourea - 5...7. Solution temperature - 20...80°C.

Technical nitric acid is used to remove nickel from aluminum and its alloys. The temperature of the acid is 50°C.

For removing copper from steel

Nitrobenzoic acid - 90, diethylenetriamine - 150, ammonium chloride - 50. Solution temperature - 80°C.

Sodium pyrosulfate - 70, ammonia (25% solution) - 330. Solution temperature - 60 °.

Sulfuric acid - 50, chromic anhydride - 500. Solution temperature - 20°C.

For removing copper from aluminum and its alloys (zinc finish)

Chromic anhydride - 480, sulfuric acid - 40. Solution temperature - 20...70°C.

Technical nitric acid. The temperature of the solution is 50°C.

For removing silver from steel

Nitric acid - 50, sulfuric acid - 850. Temperature - 80°C.

Nitric acid technical. Temperature - 20°C.

Silver is removed from copper and its alloys with industrial nitric acid. Temperature - 20°C.

Chrome is removed from steel with a solution of caustic soda (200 g/l). Solution temperature - 20 C.

Chromium is removed from copper and its alloys with 10% hydrochloric acid. The temperature of the solution is 20°C.

Zinc is removed from steel with 10% hydrochloric acid - 200 g / l. The temperature of the solution is 20°C.

Zinc is removed from copper and its alloys with concentrated sulfuric acid. Temperature - 20 C.

Cadmium and zinc are removed from any metals with a solution of aluminum nitrate (120 g/l). The temperature of the solution is 20°C.

Tin from steel is removed with a solution containing sodium hydroxide - 120, nitrobenzoic acid - 30. The temperature of the solution is 20°C.

Tin is removed from copper and its alloys in a solution of ferric chloride - 75 ... 100, copper sulfate - 135 ... 160, acetic acid (glacial) - 175. The temperature of the solution is 20 ° C.

Chemical oxidation and coloring of metals

Chemical oxidation and coloring of the surface of metal parts are intended to create an anti-corrosion coating on the surface of the parts and enhance the decorative effect of the coating.

In ancient times, people already knew how to oxidize their crafts, changing their color (silver blackening, gold coloring, etc.), burn steel objects (heating a steel part to 220 ... 325 ° C, they lubricated it with hemp oil).

Compositions of solutions for oxidation and coloring of steel (g/l)

Note that before oxidation, the part is ground or polished, degreased and decapitated.

Black color

Caustic soda - 750, sodium nitrate - 175. Solution temperature - 135°C, processing time - 90 minutes. The film is dense, shiny.

Caustic soda - 500, sodium nitrate - 500. Solution temperature - 140°C, processing time - 9 minutes. The film is intense.

Caustic soda - 1500, sodium nitrate - 30. Solution temperature - 150°C, processing time - 10 min. The film is matte.

Caustic soda - 750, sodium nitrate - 225, sodium nitrite - 60. Solution temperature - 140 ° C, processing time - 90 minutes. The film is shiny.

Calcium nitrate - 30, phosphoric acid - 1, manganese peroxide - 1. Solution temperature - 100°C, processing time - 45 min. The film is matte.

All of the above methods are characterized by a high working temperature of the solutions, which, of course, does not allow processing large parts. However, there is one "low-temperature solution" suitable for this business (g / l): sodium thiosulfate - 80, ammonium chloride - 60, phosphoric acid - 7, nitric acid - 3. Solution temperature - 20 ° C, processing time - 60 minutes . The film is black, matte.

After oxidation (blackening) of steel parts, they are treated for 15 minutes in a solution of potassium chromium peak (120 g/l) at a temperature of 60°C.

Then the parts are washed, dried and coated with any neutral machine oil.

Blue

Hydrochloric acid - 30, ferric chloride - 30, mercury nitrate - 30, ethyl alcohol - 120. Solution temperature - 20 ... 25 ° C, processing time - up to 12 hours.

Sodium hydrosulphide - 120, lead acetate - 30. Solution temperature - 90...100°C, processing time - 20...30 min.

Blue color

Lead acetate - 15 ... 20, sodium thiosulfate - 60, acetic acid (glacial) - 15 ... 30. The temperature of the solution is 80°C. The processing time depends on the intensity of the color.

Compositions of solutions for oxidation and coloring of copper (g/l)

bluish black colors

Caustic soda - 600 ... 650, sodium nitrate - 100 ... 200. Solution temperature - 140°C, processing time - 2 hours.

Caustic soda - 550, sodium nitrite - 150 ... 200. Solution temperature - 135...140°С, processing time - 15...40 min.

Caustic soda - 700...800, sodium nitrate - 200...250, sodium nitrite -50...70. Solution temperature - 140...150°С, processing time - 15...60 min.

Caustic soda - 50 ... 60, potassium persulfate - 14 ... 16. Solution temperature - 60...65 C, processing time - 5...8 min.

Potassium sulfide - 150. Solution temperature - 30°C, processing time - 5...7 min.

In addition to the above, a solution of the so-called sulfuric liver is used. Sulfur liver is obtained by fusing in an iron can for 10 ... 15 minutes (with stirring) 1 part (by weight) of sulfur with 2 parts of potassium carbonate (potash). The latter can be replaced by the same amount of sodium carbonate or caustic soda.

The glassy mass of sulfuric liver is poured onto an iron sheet, cooled and crushed to a powder. Store sulfur liver in an airtight container.

A solution of sulfuric liver is prepared in an enamel bowl at the rate of 30...150 g/l, the temperature of the solution is 25...100°C, the processing time is determined visually.

With a solution of sulfuric liver, in addition to copper, silver can be well blackened and steel satisfactorily.

Green color

Copper nitrate - 200, ammonia (25% solution) - 300, ammonium chloride - 400, sodium acetate - 400. Solution temperature - 15...25°C. The color intensity is determined visually.

Brown color

Potassium chloride - 45, nickel sulphate - 20, copper sulphate - 100. Solution temperature - 90...100°C, color intensity is determined visually.

Brownish yellow color

Caustic soda - 50, potassium persulfate - 8. Solution temperature - 100°C, processing time - 5...20 min.

Blue

Sodium thiosulfate - 160, lead acetate - 40. Solution temperature - 40 ... 100 ° C, processing time - up to 10 minutes.

Compositions for oxidation and coloring of brass (g/l)

Black color

Copper carbonate - 200, ammonia (25% solution) - 100. Solution temperature - 30 ... 40 ° C, processing time - 2 ... 5 minutes.

Copper bicarbonate - 60, ammonia (25% solution) - 500, brass (sawdust) - 0.5. Solution temperature - 60...80°С, processing time - up to 30 min.

Brown color

Potassium chloride - 45, nickel sulfate - 20, copper sulfate - 105. Solution temperature - 90 ... 100 ° C, processing time - up to 10 minutes.

Copper sulphate - 50, sodium thiosulfate - 50. Solution temperature - 60 ... 80 ° C, processing time - up to 20 minutes.

Sodium sulfate - 100. Solution temperature - 70°C, processing time - up to 20 minutes.

Copper sulphate - 50, potassium permanganate - 5. Solution temperature - 18 ... 25 ° C, processing time - up to 60 minutes.

Blue

Lead acetate - 20, sodium thiosulfate - 60, acetic acid (essence) - 30. Solution temperature - 80 ° C, processing time - 7 minutes.

3 green color

Nickel ammonium sulphate - 60, sodium thiosulfate - 60. Solution temperature - 70 ... 75 ° C, processing time - up to 20 minutes.

Copper nitrate - 200, ammonia (25% solution) - 300, ammonium chloride - 400, sodium acetate - 400. Solution temperature - 20 ° C, processing time - up to 60 minutes.

Compositions for oxidation and coloring of bronze (g/l)

Green color

Ammonium chloride - 30, 5% acetic acid - 15, medium acetic copper salt - 5. Solution temperature - 25...40°C. Hereinafter, the color intensity of bronze is determined visually.

Ammonium chloride - 16, acidic potassium oxalate - 4, 5% acetic acid - 1. Solution temperature - 25...60°C.

Copper nitrate - 10, ammonium chloride - 10, zinc chloride - 10. Solution temperature - 18...25°C.

yellow green color

Nitrate copper - 200, sodium chloride - 20. Solution temperature - 25°C.

Blue to yellow-green

Depending on the processing time, it is possible to obtain colors from blue to yellow-green in a solution containing ammonium carbonate - 250, ammonium chloride - 250. The temperature of the solution is 18 ... 25 ° C.

Patination (giving the appearance of old bronze) is carried out in the following solution: sulfuric liver - 25, ammonia (25% solution) - 10. Solution temperature - 18 ... 25 ° C.

Compositions for oxidation and coloring of silver (g/l)

Black color

Sulfuric liver - 20...80. Solution temperature - 60..70°С. Hereinafter, the color intensity is determined visually.

Ammonium carbonate - 10, potassium sulfide - 25. Solution temperature - 40...60°C.

Potassium sulphate - 10. Solution temperature - 60°C.

Copper sulphate - 2, ammonium nitrate - 1, ammonia (5% solution) - 2, acetic acid (essence) - 10. Solution temperature - 25...40°C. The content of the components in this solution is given in parts (by weight).

Brown color

A solution of ammonium sulphate - 20 g / l. Solution temperature - 60...80°С.

Copper sulphate - 10, ammonia (5% solution) - 5, acetic acid - 100. Solution temperature - 30...60°C. The content of the components in the solution - in parts (by weight).

Copper sulphate - 100, 5% acetic acid - 100, ammonium chloride - 5. Solution temperature - 40...60°C. The content of the components in the solution - in parts (by weight).

Copper sulphate - 20, potassium nitrate - 10, ammonium chloride - 20, 5% acetic acid - 100. Solution temperature - 25...40°C. The content of the components in the solution - in parts (by weight).

Blue

Sulfuric liver - 1.5, ammonium carbonate - 10. Solution temperature - 60°C.

Sulfuric liver - 15, ammonium chloride - 40. Solution temperature - 40...60°C.

Green color

Iodine - 100, hydrochloric acid - 300. Solution temperature - 20°C.

Iodine - 11.5, potassium iodide - 11.5. The temperature of the solution is 20°C.

Attention! When dyeing silver green, you must work in the dark!

Composition for oxidation and coloring of nickel (g/l)

Nickel can only be painted black. The solution (g/l) contains: ammonium persulfate - 200, sodium sulfate - 100, iron sulfate - 9, ammonium thiocyanate - 6. Solution temperature - 20...25°C, processing time - 1-2 minutes.

Compositions for the oxidation of aluminum and its alloys (g/l)

Black color

Ammonium molybdate - 10...20, ammonium chloride - 5...15. Solution temperature - 90...100°С, treatment time - 2...10 min.

Grey colour

Arsenic trioxide - 70...75, sodium carbonate - 70...75. Solution temperature - boiling, processing time - 1...2 min.

Green color

Orthophosphoric acid - 40 ... 50, acidic potassium fluoride - 3 ... 5, chromic anhydride - 5 ... 7. Solution temperature - 20...40 C, processing time - 5...7 min.

Orange color

Chromic anhydride - 3...5, sodium fluorine silicate - 3...5. Solution temperature - 20...40°С, processing time - 8...10 min.

tan color

Sodium carbonate - 40 ... 50, sodium chlorate - 10 ... 15, caustic soda - 2 ... 2.5. Solution temperature - 80...100°С, processing time - 3...20 min.

Protective compounds

Often, the craftsman needs to process (paint, cover with another metal, etc.) only part of the craft, and leave the rest of the surface unchanged.
To do this, the surface that does not need to be covered is painted over with a protective compound that prevents the formation of a particular film.

The most affordable, but not heat-resistant protective coatings- waxy substances (wax, stearin, paraffin, ceresin) dissolved in turpentine. To prepare such a coating, wax and turpentine are usually mixed in a ratio of 2: 9 (by weight). Prepare this composition as follows. Wax is melted in a water bath and warm turpentine is introduced into it. To protective compound would be contrast (its presence could be clearly seen, controlled), a small amount of dark-colored paint soluble in alcohol is introduced into the composition. If this is not available, it is easy to introduce a small amount of dark shoe cream into the composition.

You can give a recipe that is more complex in composition,% (by weight): paraffin - 70, beeswax- 10, rosin - 10, pitch varnish (Kuzbasslak) - 10. All components are mixed, melted over low heat and mixed thoroughly.

Wax-like protective compounds are applied hot with a brush or swab. All of them are designed for operating temperatures up to 70°C.
Somewhat better heat resistance (operating temperature up to 85°С) is possessed by protective compositions based on asphalt, bituminous and pitch varnishes. Usually they are thinned with turpentine in a ratio of 1:1 (by weight). The cold composition is applied to the surface of the part with a brush or swab. Drying time - 12...16 hours.

Perchlorovinyl paints, varnishes and enamels withstand temperatures up to 95°C, oil-bitumen varnishes and enamels, asphalt-oil and bakelite varnishes - up to 120°C.

The most acid-resistant protective composition is a mixture of 88N glue (or Moment) and filler (porcelain flour, talc, kaolin, chromium oxide), taken in the ratio: 1:1 (by weight). The required viscosity is obtained by adding to the mixture a solvent consisting of 2 parts (by volume) of B-70 gasoline and 1 part of ethyl acetate (or butyl acetate). The working temperature of such a protective composition is up to 150 C.

A good protective composition is epoxy varnish (or putty). Working temperature- up to 160°С.

In order to correctly and safely carry out the chrome plating process with your own hands, you should take into account all the features of the chemical and physical transformations that take place in the galvanic bath. Most of the reagents involved in chrome plating are highly hazardous substances, so before you start experimenting with chrome plating, carefully study the theoretical side of the process. Next, we will try to consider in detail the chemical component of the issue, security measures and how to make a galvanic bath and electrolyte.

Chrome plating is a physical and chemical process, during which the surface of the workpiece or part is deposited thin layer metallic chromium. This metal gives the surface a shiny look, so that the chrome-plated product takes on a very beautiful look. Electroplating opens wide opportunities to enhance decorative, physical and chemical properties materials.

Chromium is extremely resistant to aggressive environments, it does not tarnish or darken under the influence of water and air, due to which it has found wide application in the design of car body parts and parts of mechanisms operating in difficult conditions.

The thickness of the chrome coating is very small: from 0.075 to 0.25 mm. Unlike nickel, chromium in most cases is not applied directly to the metal. To do this, use a thin layer of the substrate applied by electroplating. Such a sublayer consists of copper or nickel and requires the use of additional technological operations, complicating the already difficult process of chromium plating.

Another difficulty that can stop a home craftsman from completing a task is the purchase of chemicals. The main component of chromium plating is chromium oxide (CrO 3), another name is chromic anhydride. An unpleasant feature of its use is that hexavalent chromium oxide is the strongest poison, the lethal dose of which for humans is about 6 g. This chemical compound has a limited circulation, strictly controlled by the state. Waste that occurs after the end of chrome plating must be disposed of in accordance with a special procedure, and not just poured into the sewer, or even worse - into the soil. Chromic anhydride is a carcinogen, when its solution gets on the skin, very strong irritations occur, up to eczema and dermatitis, which can develop into skin cancer.

When chromium oxide is combined with organic substances (oil, gasoline, etc.), fires and explosions occur. This substance is extremely dangerous to health and life, so before starting work, you should weigh the pros and cons, evaluating the appropriateness of such a decision.

2 Chrome plating equipment

The first thing you need for chrome plating is a well-ventilated area separate from the living quarters. You should not start experimenting at home in the kitchen, in the bathroom or in other places not intended for the operation of chemical equipment. The best choice there will be a large garage or workshop, which should first be freed from containers of gasoline, oil, paint and solvents. It would also be nice to equip a forced ventilation system. Be sure to get a fire extinguisher and think about the option of an emergency fire exit.

Chrome plating equipment includes:

• plastic galvanic bath;
• rectifier with parameters 12V/50A;
• acid-resistant heater;
• thermometer.

In addition to the plating bath, you will need several additional containers of the same size to wash the workpiece. To save time and money, it will be necessary to organize a separate electroplating bath for copper plating or nickel plating, since constantly changing reagents in one container is long and impractical.

The rectifier must be of sufficiently high power, especially if you want to do chrome plating with your own hands on medium and large sizes. Proceed in the calculations from the fact that to create a shiny surface, a current density of the order of 15-25 A / dm 2 is required, so that a conventional rectifier is able to ensure the normal conduct of the process for a maximum of overlays door handles car or small interior trim parts (gearbox knob, radio housing bezel, etc.). Big details- disks or a bumper, most likely it will not be possible to cover with chrome with your own hands, or it will cost an amount commensurate with the purchase of new spare parts.

As for the heater, in some sources it is recommended to use a conventional heating element. I would like to strongly caution against this solution, since chromium plating requires acid-resistant equipment, the heating element is not such a device, and its use will entail, at best, a breakdown of the electrolytic cell.

The most common thermometer can be used, with divisions from 0 to 100 ° C. The temperature at which the process proceeds evenly is 47-52°C, the main task will be to establish and maintain these parameters stable throughout the entire reaction time.

3 Electrolyte reagents

The chromium plating process is carried out by electroplating. For its implementation, it is necessary to have a cathode, an anode (workpiece) and an electrolyte, in the environment of which chemical reactions will occur. Assembling a device for chromium plating is quite simple, especially if before that you already had experience in creating copper or nickel coatings: the technology is similar, only the parameters of the environment, electrolyte composition and cathode material differ.

A sheet of lead or its alloy with tin is used as the cathode. It is best that the lead plate be slightly larger than the workpiece. The cathode is connected to the positive electrode of the rectifier.

The anode is connected to the material to be chrome plated. It must be “suspended” in the electrolyte medium in such a way that it does not touch the walls, the bottom, and in no case touches the cathode.

The creation of an electrolyte requires the following components:

• chromic anhydride, at the rate of 250 g/l electrolyte;
• sulfuric acid - 2-2.5 g/l;
• distilled or pure, iron-free water.

Before you make an electrolyte, heat the water to a temperature of 60-80 ° C, then dissolve chromic anhydride in it. Let the mixture cool slightly and slowly add required amount pure sulfuric acid. Acid should not be technical, but pure and concentrated.

Electroplating is very sensitive to the composition of the electrolyte, so chromium plating enterprises have entire laboratories that constantly monitor the stability of the reagents. When chrome plating with your own hands, you will have to do without the help of chemists and technologists, but if there are few parts to be processed, then the composition of the electrolyte should change uncritically.

4 Surface preparation and how chromium plating proceeds

Self-plating with chromium is impossible without proper preparation of the surface of the product. First you need to create a copper or nickel substrate, since chrome will not lie on the surface of steel, aluminum or any other metal. Copper plating or nickel plating is carried out in a galvanic bath, while the cathode is, respectively, metallic copper or nickel, the electrolyte is a solution of sulfuric acid and blue vitriol or nickel salts. After completion of the preparation, the product is carefully ground and polished, trying not to damage the thin layer of the substrate, degreased and dried.

Independent chromium plating should take place at stable parameters of voltage, temperature and electrolyte composition. Any deviation can lead to coating defects. For example, an excess of the current concentration per unit area leads to the formation of outgrowths and dendrites of metallic chromium at the sharp corners of the products. Violation of the temperature regime, as well as fluctuations in the concentration of reagents, cause darkening, dullness or spotting of the coating.

After the parts are chromed at home, the chromed surface is covered with a sufficient layer of metal, the voltage is turned off, the product is disconnected and placed in a bath of distilled water. It is better to repeat the process several times, each time changing the water.

Before you start chrome plating with your own hands, you should carefully evaluate the future cost of the work and draw a conclusion about their feasibility. If you do not have a place to conduct such experiments: for example, your garage or workshop, then you should not start, otherwise you can greatly harm others.

Before you make a chrome plating device, think and plan for future waste disposal.

Under no circumstances should the spent electrolyte be discharged into the sewer or the soil!

When hit in ground water, and then into the wells, chromium oxide causes poisoning and the development of oncological diseases, therefore it is strongly recommended not to start work without having previously decided on all the intricacies of the process.

Chrome plated items look beautiful and are very often used to decorate motorcycles, cars or sports bikes. But few people think that chrome plating of parts is necessary not only to give beauty to the product: with the help of various types of this process, it is possible to give additional qualities to metal parts and provide protection against corrosion.

What is the application of chromium to the surface

All types of chromium plating can be conditionally divided into:

• decorative;
• hard.

Aesthetic direction

Decorative chrome plating is carried out in order to give the details a stylish beautiful look. Very often, decorative chrome plating is used for tuning. various parts car or to create souvenirs and beautiful household items. Well-conducted metallization, in addition to decorative qualities, may have protective properties. The technology of decorative chrome plating can be of the following types:

hard chrome variant

Hard chrome plating is often used for such purposes:

According to the technology of hard chromium coating deposition, it is possible to distinguish different methods.

Galvanic

With this application of chromium, the product is immersed in a container with a reagent containing all the necessary components and heated to a certain temperature. A transformer is connected to it using a set of electrodes and a physico-chemical process occurs when reagents are created on the surface under the influence of current. protective film. The thickness of such a film depends on the time of galvanization and on the magnitude of the current.

The calculation of the process parameters is carried out depending on:

• type of metal (copper, iron or aluminum);
• degree of wear (new or damaged);
• nature of operation (shafts, rods or motor cylinders must be processed to the maximum).

In addition, the calculation is affected by the temperature of the reagent: the higher it is, the more actively the reaction proceeds.

Catalytic

Catalytic chromium plating involves reduction with silver and ammonia salts. This method well restores and protects against wear those things that are not subjected to mechanical stress, such as mirrors made of aluminum and copper or other household items. This chromium plating is often carried out by hand or in private workshops using a portable chromium plating machine.

Using the catalytic metallization method, you can also paint the car body by contacting a workshop where there is an appropriate apparatus. There they will be able to make a metallized body painting, choosing the color in accordance with what is indicated in the TCP. The cost of the work will be about the same as with conventional painting, but this automotive coating will make the metal immune to corrosion. Spraying can be carried out not only with chromium, but also with copper, zinc or aluminum.

Vacuum

Another option is vacuum chromium plating. This chromium plating process is possible only in the factory, in special vacuum chambers.

The principle is that a product coated with a reagent (more often chromium, but it can be copper or zinc) is placed in a special chamber. Air is pumped out of the chamber, negative pressure is created, and the reagent begins to interact with the base. The calculation of pressure and time of spraying is carried out taking into account all components of the process:

• purpose of the part;
• the degree of its deterioration;
• reagent used (copper, chromium, aluminum or combinations thereof).

Chrome plating is one of the most effective. It is this method that most often protects and restores such car parts as shafts, rods and engine cylinders. Trunks of hunting and underwater guns are recommended to be processed using this technology.

Thermochemical

The method is one of the most simple ways coating things with a necessary component, such as chrome, aluminum, silver or copper. The use of this method for metallization of products in a muffle furnace is possible only if they are not subjected to strong mechanical stress and have a heat-resistant base.

A mixture of metal chips with a combustible substance is applied to the base. Under the influence of high temperatures, the substances burn out, and the metal spreads over the surface. The disadvantage of this method is that the material is distributed unevenly, additional grinding is required, and the protective properties of the coating are weak.

What you need to chrome yourself

To do your own plating of chrome, copper, zinc or aluminum on surfaces various products, necessary:

1. Purchase or make your own equipment for chrome plating and know the features of its application.
2. Have a good idea of ​​the chromium plating process, as well as be able to calculate the time, taking into account the reagent used and the nature of the material being processed, the degree of wear.
3. Stock up on the necessary set of reagents for carrying out protective and recovery reactions, as well as for decorating.
4. Get trained in chrome plating. Having such a certificate is important if you plan to use equipment for small businesses. It is a mandatory requirement, because special knowledge is needed there: how to calculate the combination of all physico-chemical components, which reagents are better to use to obtain the optimal result.

The basis of the spraying installation

The set of purchased equipment for chromium plating, as a rule, includes additional components that provide:

• cleaning from mechanical impurities;
• grinding;
• washing and degreasing surfaces.

Also, factory spraying machines often have a calculation table in the attached instructions for most of the materials used. Such a table is a handy tool for beginners when you need to calculate the time and force of the reagent on various items, and especially on car parts when hard chrome plating is carried out. It is especially important to calculate the ratio of active spraying components, the exposure time and temperature regime for stressed automotive parts such as shafts, rods or cylinders.

For gun barrels, the requirements are less stringent, but it is also advisable to carefully process them, because hunting guns are affected by powder gases, and underwater guns are affected by high humidity.

Operating principle

Chrome plating equipment works simply. The installation performs a number of actions:

• cleans the base from irregularities and residues of colorants;
• grinds to smoothness;
• degreases;
• applies a layer of primer;
• subjects the thing to heat treatment for more reliable adhesion of the primer base to the surface.

Chrome plating is one of the most optimal protective means for protecting automotive components from overloads, and gun barrels from adverse effects. Chrome plating also makes it possible to create beautiful souvenirs or things to decorate the interior.