The site outlines the basics of electroplating technology. The processes of preparation and application of electrochemical and chemical coatings, as well as methods of coating quality control are considered in detail. The main and auxiliary equipment of the electroplating shop is described. Information on the mechanization and automation of galvanic production, as well as sanitation and safety precautions is given.

The site can be used for vocational training of workers in production.

The use of protective, protective-decorative and special coatings makes it possible to solve many problems, among which an important place is occupied by the protection of metals from corrosion. Corrosion of metals, i.e., their destruction due to the electrochemical or chemical action of the environment, causes enormous damage to the national economy. Every year, as a result of corrosion, up to 10-15% of the annual output of metal in the form of valuable parts and structures, complex instruments and machines goes out of use. In some cases, corrosion leads to accidents.

Electroplated coatings are one of the effective methods of corrosion protection, they are also widely used to impart a number of valuable special properties to the surface of parts: increased hardness and wear resistance, high reflectivity, improved anti-friction properties, surface electrical conductivity, easier solderability, and, finally, simply to improve the external type of products.

Russian scientists are the creators of many important methods of electrochemical processing of metals. Thus, the creation of electroforming is the merit of Academician B. S. Jacobi (1837). The most important work in the field of electroplating belongs to the Russian scientists E. Kh. Lenz and I. M. Fedorovsky. The development of electroplating after the October Revolution is inextricably linked with the names of scientific professors N. T. Kudryavtsev, V. I. Liner, N. P. Fedotiev and many others.

Much work has been done to standardize and normalize coating processes. The sharply increasing volume of work, the mechanization and automation of electroplating shops required a clear regulation of processes, careful selection of electrolytes for coating, selection of the most effective methods for preparing the surface of parts before the deposition of electroplated coatings and final operations, as well as reliable methods for quality control of products. Under these conditions, the role of a skilled electroplating worker increases sharply.

The main objective of this site is to help students of technical schools in mastering the profession of an electroplating worker who knows modern technological processes used in advanced electroplating shops.

Electrolytic chromium plating is an effective way to increase the wear resistance of rubbing parts, protect them from corrosion, as well as a method of protective and decorative finishing. Significant savings are provided by chrome plating when restoring worn parts. The process of chromium plating is widely used in the national economy. A number of research organizations, institutes, universities and machine-building enterprises are working on its improvement. More efficient electrolytes and chromium plating modes are emerging, methods are being developed to improve the mechanical properties of chrome parts, as a result of which the scope of chromium plating is expanding. Knowledge of the basics of modern chromium plating technology contributes to the fulfillment of the instructions of normative and technical documentation and the creative participation of a wide range of practitioners in the further development of chromium plating.

The site developed the issues of the effect of chromium plating on the strength of parts, expanded the use of efficient electrolytes and technological processes, introduced a new section on methods to improve the efficiency of chromium plating. The main sections have been redesigned taking into account the nporpecsivnyh advances in chrome plating technology. The given technological instructions and designs of hanging fixtures are exemplary, guiding the reader in matters of choosing chrome plating conditions and in the principles of designing hanging fixtures.

The continuous development of all branches of mechanical engineering and instrument making has led to a significant expansion of the field of application of electrolytic and chemical coatings.

By chemical deposition of metals, in combination with galvanic metal coatings are created on a wide variety of dielectrics: plastics, ceramics, ferrites, glass-ceramic and other materials. The manufacture of parts from these materials with a metallized surface ensured the introduction of new design and technical solutions, an improvement in the quality of products and a reduction in the cost of production of equipment, machines, and consumer goods.

Parts made of plastics with metal coatings are widely used in the automotive industry, the radio engineering industry and other sectors of the national economy. The processes of metallization of polymeric materials have become especially important in the production of printed circuit boards, which are the basis of modern electronic devices and radio engineering products.

The brochure provides the necessary information about the processes of chemical-electrolytic metallization of dielectrics, the main regularities of the chemical deposition of metals are given. The features of electrolytic coatings during metallization of plastics are indicated. Considerable attention is paid to the technology of production of printed circuit boards, as well as methods for analyzing solutions used in metallization processes, as well as methods for their preparation and correction.

In an accessible and entertaining way, the site introduces physical nature in terms of the features of ionizing radiation and radioactivity, the effect of various doses of radiation on living organisms, methods of protection and prevention of radiation hazard, the possibilities of using radioactive isotopes to recognize and treat human diseases.

K.: Technika, 1989. - 191 p.
ISBN 5-335-00257-3
Download(direct link) : sputnik_galvanika.djvu Previous 1 .. 8 > .. >> Next

In electrochemical milling, a coating of any acid-resistant paint applied by a stencil can serve as a protective coating. The pickling solution in this case consists of 150 g/l sodium chloride and 150 g/l nitric acid. Etching occurs at the anode at a current density of 100–150 A/dm2. Copper plates are used as the cathode. After the termination of the process, the cathodes are removed from the bath.

Electrochemical milling is more accurate than chemical milling.

PRE-TREATMENT OF ALUMINUM AND ITS ALLOYS

To ensure strong adhesion of the electrolytic coating to aluminum, an intermediate layer of zinc, iron or nickel is applied to the surface of the latter (Table 21).

CHEMICAL AND ELECTROCHEMICAL POLISHING

A smooth metal surface can be obtained by chemical or electrochemical (anodic) polishing (Tables 22, 23). The use of these processes makes it possible to replace mechanical polishing.

When aluminum is oxidized, mechanical polishing is not enough to achieve a shiny surface; after it, chemical polishing is necessary.

21. Solutions for aluminum pretreatment

Orthophosphoric acid Glacial acetic Orthophosphoric acid

280-290 15-30 1-6

Acid Orange * For:

dye 2

pinned surface

1st intermediate processing

ratu-ra. WITH

4. orthophosphorus!

Triethane! lamin

500-IfXX) 250-550 30-80

Triethanolamine Catalin BPV

850-900 100-150

Orthophs ph rthic acids Chromic thydrnd

* Products ps mining are processed by flushing in the same mine 6A / dm2

trochemical polishing When polishing precious metals by chemical or electrochemical methods, their losses are completely eliminated. Electrochemical and chemical polishing can be not only a preparatory operation before applying electroplating, but also the final stage of the technological process. It is most widely used for aluminum. Electrochemical polishing is more economical than<ими-ческое.

The current density and duration of the electropolishing process are selected depending on the shape, size and material of the products.

COATING PROCESS TECHNOLOGY

SELECTION OF ELECTROLYTES AND PROCESSING MODES

The quality of the metal coating is characterized by the structure of the precipitate, its thickness and uniformity of distribution on the surface of the product. The structure of the precipitate is influenced by the composition and pH of the solution, the hydrogen released together with the metal, the electrolysis mode - dark

polishing

M41
with SS
Density
„|§..
cathodes

From sent
carbonaceous

I-IL
15-18
1,63-1,72
12XI8H9T, over

1-5
10-100

From steel 12X18H97
H:rusty1d

From styles 12X18H9T Aluminum and 3-5 20-50 - (aluminum) stainless

0.5-5.0 20-50 1.60-1.61 From copper or evine Copper

temperature, density of the goka, the presence of swing, filtration and 1. d.

To improve the structure of the precipitate, various organic additives (glue, gelatin, saccharin, etc.) are introduced into electrolytes, complex salts are precipitated from solutions, the temperature is increased, continuous filtration is used, etc. The released hydrogen can be absorbed by the precipitate, contributing to an increase in brittleness and porosity. , and the appearance of so-called pitting points. To reduce the effect of hydrogen on the quality of the precipitate, the parts are shaken during the process, oxidizing agents are introduced, the temperature is increased, etc. The porosity of the precipitate decreases with increasing thickness.

The uniform distribution of the precipitate on the surface and delirium depends on the scattering ability of the electrolyte. Alkaline and cyanide electrolytes have the best scattering ability, acidic electrolytes are much less, and chromium electrolytes are the worst.

When choosing an electrolyte, it is necessary to take into account the configuration of the products and the requirements that apply to them. For example, when coating products of a simple shape, you can work with simple in composition electr>-

lantamn that do not require heating, ventilation, filtration; when coating products of complex shape, solutions of complex metal salts should be used; for coating internal and hard-to-reach surfaces - internal and additional anodes, filtration, mixing; to obtain a brilliant coating - electrolytes with complex brightening and leveling additives, etc.

GENERAL SCHEME OF THE TECHNOLOGICAL PROCESS

The coating process consists of a series of sequential operations - preparatory, coating and final processing. Preparatory operations include machining [parts, degreasing in organic solvents, chemical or electrochemical degreasing, etching and polishing. The final processing of coatings includes dehydration, clarification, passivation, impregnation, polishing, brushing. After each operation

Electrochemical dimensional processing is based on local anodic dissolution of the workpiece material in an electrolyte solution with intensive movement of the electrolyte between the electrodes.

The workability of metals and alloys by the electrochemical method depends on their chemical composition and does not depend on their mechanical properties and structural state. The advantages of the method include high surface quality with an increase in processing productivity, the absence of thermal effects on the part, and the absence of tool electrode wear. Due to this, during electrochemical processing, a layer of a modified structure is not formed and the formation of burns, cracks, residual stresses, etc. on the surface is excluded.

Appropriateness of application

The use of electrochemical processing is highly efficient and economically feasible in the following main cases:

1. for processing parts made of especially hard, brittle or viscous materials (heat-resistant, hard and titanium alloys, stainless and hardened steels);
2. for processing structurally complex assemblies and parts (blades of gas turbines, dies, molds, casting molds, internal channels and cavities, etc.) even from materials that can be cut;
3. to replace particularly time-consuming (including manual) operations (deburring, rounding edges, etc.);
4. to obtain a high-quality, including a polished surface without defects in the surface layer.

Known varieties of electrochemical processing should be classified according to two defining features - the mechanism of the metal destruction process itself and the method of removing reaction products from the working zone. Based on this, we can name three main directions in which the development and implementation of electrochemical processing methods is going on: electrochemical-hydraulic (anodic-hydraulic) processing, electrochemical-mechanical processing and combined processing methods.

Electrochemical hydraulic processing

Electrochemical hydraulic processing (also called electrochemical processing in a flowing electrolyte) is based on the anodic dissolution of the metal and the removal of reaction products from the working area by the electrolyte flow. At the same time, the speed of the electrolyte flow in the interelectrode gap is maintained within 5-50 m/s (by means of a pump providing a pressure of 5-20 kgf/cm2, or due to the rotation of the cathode-tool continuously wetted by the electrolyte). The operating voltage is maintained within 5-24 V (depending on the material and the technological operation), the gap between the electrodes is from 0.01 to 0.5 mm; the size of the gap is regulated by automatic tracking systems. As a material for the manufacture of the tool electrode, stainless steel, brass, graphite are used (the latter when processed at alternating or pulsed voltage).

The energy intensity of this group of processes depends on the chemical composition of the processed material and the current efficiency. For most technological operations, it is 10-15 kWh/kg. The following types of electrochemical hydraulic processing are currently the most common.

Copy-piercing operations carried out with the translational movement of the cathode-tool, the shape of which is copied on the product simultaneously over the entire surface (Fig. 5).

These operations are used in the manufacture of turbine blades, forging dies, etc. At a metal removal rate of 0.1-0.5 mm/min, a surface finish of 6-7 is achieved; with an increase in processing speed up to 1-2 mm/min, the surface finish increases to 8-9. The highest productivity obtained when processing cavities on the machine model MA-4423 is 15000 mm3/min at a current of 5000 a. The feed rate of the tool in the direction of metal removal is 0.3-1.5 mm/min when processing dies, molds and blades and 5-6 mm/min when piercing holes. Surface finish 6-9; processing accuracy 0.1-0.3 mm. Processing is carried out with minimal gaps (0.1-0.15 mm); the largest gaps (5-6 mm) - with the simultaneous processing of large surfaces.

Rice. 5. Scheme of flashing a hole by the electrochemical method

Rice. 6. Machining with a rotary disc tool

Machining with a rotating disc tool (Fig. 6), which allows for profile, flat and circular external grinding with a non-abrasive tool to obtain a surface finish of 7-9 with a capacity of up to 150-200 mm3/min on stainless steels from a working area of ​​1 cm2 and 60-80 mm3/min for hard alloys, used to obtain a profile of carbide threaded dies, shaped cutters, knurling rollers, making external slotted grooves, cutting narrow slots, cutting workpieces (cutting width 1.5-2.5 mm; surface finish 6-7) , as well as for the processing of permanent magnets. Processing is carried out with gaps of 0.01-0.1 mm; machining accuracy 0.01-0.05 mm, surface finish 6-9. The feed rate, depending on the depth of processing, ranges from 1 to 40 mm / min, the voltage is 6-10 V. When machining a hard alloy, alternating or pulsed current is used.

Rice. 7. Scheme of electrochemical deburring: 1 - tool; 2 - insulating sleeve; 3-blank (anode); 4 - burr to be removed

Wire complex contour cutting of products from hardened, stainless steels and other hard-to-cut materials on a copier makes it possible to produce stamp matrices, templates, through and blind grooves. Machining capacity up to 40 mm2/min with surface finish 8 - 9. Machining accuracy for straight cutting 0.02 mm, for contour cutting 0.06 mm. The maximum thickness of the workpiece being cut is 20 mm (the given data were obtained on the MA-4429 machine).

Removing burrs from gears (Fig. 7), parts of hydraulic equipment, small radio products, etc.

Production of grooves in special products.

Figured processing of bodies of revolution both along the end of the product, and outside and inside. The accuracy of processing when using a shaped cathode is 0.05-0.1 mm.

Electrochemical mechanical processing

Electrochemical mechanical treatment is based on the anodic dissolution of the metal and the removal of reaction products from the treated surface and from the working area using an abrasive and an electrolyte flow. This type of processing includes electrochemical grinding (electroabrasive or electrodiamond machining), electrochemical machining with a neutral abrasive (grinding, honing and polishing) and anode abrasive machining. In electroabrasive and electrodiamond machining, metal removal is carried out not only due to the anodic dissolution reaction, but also by abrasive or diamond grains.

Performance in electrodiamond grinding of hard alloys is 1.5-2 times higher than in diamond grinding, and the wear of the diamond wheel is 1.5-2 times less (when working with wheels on a bronze bond Ml, on bonds M5, MV1 and MO13E, wheel wear approximately the same as for diamond grinding); the surface finish is the same as diamond grinding. In electrochemical grinding, the power consumed to drive the grinding wheel is reduced by several times. At the same time, the temperature of the surface layer decreases sharply, due to which the appearance of cracks and burns is completely eliminated. This method is widely used for sharpening carbide tools.

Electrochemical machining with neutral abrasive finds application for flat, cylindrical and profile grinding, honing of internal cylindrical surfaces, superfinishing. In all cases, the productivity of these operations is four to eight times greater than that of machining.

Combined processing methods

Combined processing methods include electroerosion-chemical and electrochemical - ultrasonic.

The electroerosive-chemical treatment method is based on the simultaneous occurrence of the processes of anodic dissolution and erosion destruction of the metal and the removal of reaction products from the working zone by the electrolyte flow. During piercing operations, the cathode feed rate reaches 50-60 mm/min for steel, 20-30 mm/min for high-temperature alloys and 10 mm/min for hard alloys. In this case, the wear of the cathode-tool does not exceed 2.5%; processing accuracy 0.1-0.4 mm (according to experimental data).

This method can also be used for circular, flat and profile grinding, cutting workpieces from hard-to-cut materials. When cutting stainless steel workpieces, the productivity is 550-800 mm2/min; tool wear in this case reaches 4-5%; processing accuracy 0.1-0.3 mm. Machines for this processing method are currently not available.

The electrochemical method of processing is based on the destruction of the metal by its simultaneous anodic dissolution and exposure to ultrasonic vibrations. This method is used for processing hard metal drawing dies.

Chemical methods of processing materials are called, in which the removal of a layer of material occurs due to chemical reactions in the processing zone. Advantages of chemical processing methods: a) high productivity, provided by relatively high reaction rates, primarily the lack of dependence of productivity on the size of the treated surface area and its shape; b) the possibility of processing especially hard or viscous materials; c) extremely low mechanical and thermal effects during processing, which makes it possible to process parts of low rigidity with a sufficiently high accuracy and surface quality.

Dimensional deep etching (chemical milling) is the most common chemical processing method. It is advisable to use this method for processing surfaces of complex shapes on thin-walled parts, obtaining tubular parts or sheets with a smooth change in thickness along the length, as well as when processing a significant number of small parts or round blanks with large; the number of processed places (perforation of cylindrical surfaces of pipes). By local removal by this method from excess material in unloaded or lightly loaded aircraft and missiles, the overall weight can be reduced without reducing their strength and rigidity. In the United States, the use of chemical milling has reduced the weight of a supersonic bomber wing by 270 kg. This method allows you to create new structural elements, such as sheets 1 of variable thickness. Chemical milling is also used in the manufacture of printed circuits for electronic equipment. In this case, the sections specified by the scheme are removed from the panel of insulating material, covered on one or both sides with copper foil, by etching.

The technological process of chemical milling consists of the following operations.

1. Preparation of parts for chemical milling to ensure subsequent tight and reliable adhesion of the protective coating to the surface of the part. For aluminum alloys, this preparation is carried out by: degreasing in B70 gasoline; light pickling in a bath with caustic soda 45-55 g/l and sodium fluoride 45-55 g/l at a temperature of 60-70 ° C for 10-15 minutes to remove the clad layer; washing in warm and cold water and clarification in nitric acid, followed by washing and drying. For stainless and titanium alloys, parts are prepared by pickling to remove scale in a bath with hydrofluoric (50-60 g/l) and nitric (150-160 g/l) acids or in a bath with electric heating up to 450-460 ° C in caustic soda and sodium nitrate (20%) followed by washing and drying, degreasing and light pickling followed by repeated washing and drying.

2. Application of protective coatings to the places of the workpiece that are not subject to etching. It is produced by installing special overlays, chemically resistant adhesive-type templates or, most often, by applying paint coatings, which are usually used as perchlorovinyl varnishes and enamels, polyamide varnishes and materials based on non-prene rubbers. So, for aluminum alloys, PKhV510V enamel, RS1 solvent TU MHP184852 and KhV16 enamel TU MHPK-51257, R5 TU MHP219150 solvent are recommended, for titanium alloys - AK20 glue, RVD thinner. For better adhesion of these coatings to metal, anodizing of the surface is sometimes preliminarily performed. The application of paint and varnish coatings is carried out with brushes or spray guns with preliminary protection of the places of etching with templates or by immersion in a bath; in the latter case, the contour is marked on the dried protective film, then it is cut and removed.

3. Chemical dissolution is carried out in baths in compliance with the temperature regime. Chemical milling of aluminum and magnesium alloys is carried out in solutions of caustic alkalis; steels, titanium, special heat-resistant and stainless alloys - in solutions of strong mineral acids.

4. Cleaning after etching of parts made of aluminum alloys with an enamel protective coating is carried out by washing in running water at a temperature of 50 + 70 ° C, soaking the protective coating in hotter running water at a temperature of

70-90 ° С and subsequent removal of the protective coating with knives manually or with soft brushes in a solution of ethyl acetate with gasoline (2: 1). Then produce clarification or light etching and drying.

The quality of the surface after chemical milling is determined by the initial surface roughness of the workpiece and the etching modes; usually it is 1-2 classes lower than the cleanliness of the original surface. After etching, all defects previously present on the workpiece. (risks, scratches, irregularities) retain their depth, but broaden, acquiring greater smoothness; the greater the depth of etching, the more pronounced these changes. The quality of the surface is also affected by the method of obtaining blanks and their heat treatment; rolled material gives a better surface than stamped or pressed material. Large surface roughness with pronounced irregularities is obtained on cast billets.

The surface roughness is affected by the structure of the material, grain size and orientation. Hardened aluminum sheets subjected to aging have a higher surface finish class. If the structure is coarse-grained (for example, the metal is annealed), then the finished surface will be with large roughness, uneven, bumpy. The fine-grained structure should be considered the most suitable for chemical processing. Carbon steel blanks are best treated by chemical milling before hardening, since in the case of hydrogenation during pickling, subsequent heating helps to remove hydrogen. However, it is desirable to harden thin-walled steel parts before chemical treatment, since subsequent heat treatment can cause them to deform. The surface treated by chemical milling is always somewhat loosened due to pickling, and therefore this method significantly reduces the fatigue characteristics of the part. Given this, for parts operating under cyclic loads, it is necessary to carry out polishing after chemical milling.

Chemical milling accuracy ±0.05 mm po. depth and not less than +0.08 mm along the contour; the radius of curvature of the cutout wall is equal to the depth. Chemical milling is usually performed to a depth of 4-6 mm and less often up to 12 mm; with a larger milling depth, the surface quality and machining accuracy deteriorate sharply. The minimum final thickness of the sheet after etching can be 0.05 mm, therefore, chemical milling can process parts with very thin bridges without warping, and perform conical processing by gradually immersing the part in the solution. If it is necessary to pickle from two sides, you must either position the workpiece vertically so as to allow the released gas to freely rise from the surface, or pickle in two steps - 1 first on one side and then on the other. The second method is preferable, since with a vertical arrangement of the workpiece, the upper edges of the cutouts are processed worse due to gas bubbles entering there. In the manufacture of deep cuts, special measures (for example, vibrations) should be used to remove gas from the machined surface, which prevents the normal process from being carried out. Depth control, etching during processing is carried out by immersion Simultaneously with the preparation of control samples, direct control of dimensions by thickness gauges such as an indicator bracket or electronic ones, as well as by automatic weight control.

The productivity of chemical milling is determined by the rate of material removal in depth. The rate of etching increases with an increase in the temperature of the solution by about 50-60% for every 10 ° C, and also depends on the type of solution, its concentration and purity. Mixing of the solution during the pickling process can be done with compressed air. The etching process is determined by an exothermic reaction, so the supply of compressed air cools it somewhat, but basically the temperature constancy is ensured by placing water coils in the bath.

Etching by immersion has a number of disadvantages - the use of manual labor, partial breakdown of protective films on untreated surfaces. When processing a number of parts, the jet etching method is more promising, in which alkali is supplied by nozzles.

A means of increasing the productivity of chemical milling is the use of ultrasonic vibrations with a frequency of 15-40 kHz; in this case, the processing productivity increases by 1.5-2.5 times - up to 10 mm/h. The process of chemical treatment is also greatly accelerated by the influence of infrared radiation of directional action. Under these conditions, there is no need to apply protective coatings, since the metal is subjected to strong heating along a given heating circuit, the remaining areas, being cold, practically do not dissolve.

The etching time is set empirically on control samples. The pickled workpieces are removed from the pickling machine, washed in cold water, and to remove the emulsion, paint and BF4 glue, they are treated at a temperature of 60-80 ° C in a solution containing 200 g/l of caustic soda. The finished parts are thoroughly washed and dried in a stream of air.

Improving the conditions for roughing workpieces by cutting by first removing the crust by etching is another example of the dissolving action of a reagent. Before pickling, the workpieces are blown with sand to remove scale. Etching of titanium alloys is carried out in a reagent consisting of 16% nitric and 5% hydrofluoric acids and 79% water. According to foreign literature, for this purpose, etching in salt baths is used, followed by washing in water and then repeated etching in acid etchants for final surface cleaning.

The chemical impact of the technological environment is also used to improve conventional cutting processes; methods of processing materials based on a combination of chemical and mechanical effects are increasingly being used. Examples of already mastered methods are the chemical-mechanical method of grinding hard alloys, chemical polishing, etc.

B. Rau

Processes electrochemical processing of metals are used in all industries. With their help, you can perform operations such as drilling, turning, grinding or polishing, milling parts of the most complex configurations, and even remove burrs. In this case, the essence of the processes of electrochemical dimensional processing is the anodic dissolution of the metal during electrolysis with the regular removal of the resulting waste. And therefore - and this is the most valuable - for the processes of electrochemical "cutting" there are practically no hard-to-cut metals.
Everything these advantages of electrochemical processing processes can be successfully used at home for many interesting and useful jobs. For example, with their help, it is possible to cut an elastic plate from a razor blade in 20-30 minutes, cut a hole of complex shape in a thin sheet of metal, carve a spiral groove on a round rod. To perform all these works, it is enough to have an AC rectifier that gives an output voltage of 6-10 volts, or a rectifier for micromotors of 6 volts, or, finally, a set of 2-3 batteries for a flashlight. Pieces of wire, metal, glue and other auxiliary materials can be found in any home workshop.

Milling.

If in some blank you need to make a deepening of a complex configuration - for example, cut out the apartment number - then for this you need to take a sheet of drawing paper and draw on it a life-size contour of the deepening that you want to get. Then, with a razor blade or scissors, cut and remove the drawn outline, and cut the sheet in accordance with the shape and size of the workpiece. Glue the mask template (1) obtained in this way with rubber glue or BF-88 glue onto the surface of the workpiece (2), attach the wire from the positive pole of the rectifier or a set of batteries to the workpiece and apply 1-2 layers to all its surfaces remaining without insulation any varnish or nitro paint. It's a good idea to varnish or paint the mask template itself. After allowing the coating to dry, lower the workpiece into a glass with a concentrated solution of common salt, place a cathode plate (3) of any metal opposite the mask template and connect it to the negative pole of the rectifier or current source.
How as soon as the current is turned on, the process of electrochemical dissolution of the metal inside the contour of the mask template will begin. But after some time, the intensity of the process will decrease, which can be seen from the decrease in the number of bubbles released on the cathode (3). This means that an insulating layer of process waste has formed on the treated surface. To remove them and at the same time measure the depth of the recess, the part must be removed from the glass and, trying not to damage the mask template, clean off the loose layer of waste from the surface to be treated with a small hard brush. After that, periodically removing the part to control the dimensions and remove waste, the process can be continued until the depth of the recess reaches the required value. And when the processing is completed, having removed the insulation and mask template, the part must be washed with water and lubricated with oil to prevent corrosion.

Stamping and engraving.

When in a thin sheet of metal it is necessary to make a hole of complex configuration, the principles of electrochemical processing remain the same as in milling. The only subtlety is that in order for the edges of the hole to be even, the mask template (1) must be glued onto the workpiece from both sides. To do this, the contours of the mask template (1) should be cut out in a sheet of paper folded in half and, sticking the template on the workpiece (2), orient it along one of its sides. And besides, in order to speed up processing and ensure uniform removal of metal from both sides, it is advisable to bend the cathode plate (3) in the form of the letter "U" and place the workpiece to be processed into it.
For the manufacture of sheet steel - for example, from the blade of a razor blade - parts of any profile act somewhat differently. The profile of the part itself is cut out of paper (1) and glued to the workpiece (2). Then the entire opposite side of the steel sheet is varnished, and on the side of the template, varnish insulation is applied so that it does not adjoin the template. And only in one place the applied insulation needs to be brought to the template with a narrow jumper (3) - otherwise the dissolution of uninsulated surfaces around the template may end before the contour of the part is formed. To obtain more accurate details, two templates can be cut out, glued to the workpiece on both sides and processed in a U-shaped cathode. In similar ways, you can make various inscriptions on metal, both convex and "depressed".

Threading and spiral grooves.

One A variation of the milling process is electrochemical spiral grooving and threading. This method can be useful for making at home, for example, wood screws or twist drills. When cutting a thread on a screw, as a mask template (1), you need to take a thin rubber cord of square section 1x1 mm, wind it in a spiral on a cylindrical workpiece (2) with tension and fasten its ends with threads (3). And then those surfaces of the workpiece that are not subject to etching, isolate with varnish. As a result of electrochemical processing, a spiral thread cavity is formed on the workpiece between the turns of rubber. Now you need to sharpen or, more precisely, make that end of the workpiece conical, which will serve as the sting of the screw entering the tree. To do this, the workpiece must be removed from the bath, remove the rubber from it and dry it. And then, varnishing its surface in such a way that only the first 2-3 threads of the thread remain open, the workpiece is returned to the bath and the electrochemical treatment is continued for some more time.
For for making a twist drill at home, as a mask template (1), you need to take three rubber cords of the same section and wind them onto a heat-treated cylindrical workpiece (2), but already in two passes. Then, the surfaces of the workpiece that are not subject to processing, and for reliability, the rubber cords must also be varnished and, lowering the part into a glass-bath, electrochemical milling of the drill grooves to the desired depth should be carried out. Now these grooves need to be widened to form the so-called "back" of the drill (3). To do this, two out of three cords are removed from each strip of rubber insulation, and electrochemical milling continues for some more time. After that, removing the remaining insulation and sharpening the lead, you will get an excellent twist drill.

Grinding.

To to grind the surface of cylindrical parts by electrochemistry, in addition to traditional equipment, you must have a small electric motor or drill. After pre-isolating with varnish the surfaces of the part that cannot be processed, fix it on the motor shaft (1), install the engine vertically on some bracket and lower the end of the part to be machined (2) into the bath with electrolyte. In this case, it is best to organize the power supply of the anode part (2) with a sliding contact going to the motor shaft, and make the cathode (3) flat, equal in length to the treated surface. Now it remains to turn on the electric motor and power the bath. With the beginning of the process, the darkening of the surface will begin - the formation of waste. To obtain the correct cylindrical shape of the treated surface, these wastes must be continuously removed. It is convenient to do this with a toothbrush with a bristle shortened for rigidity, which, pressed against the part, should be moved up and down measuredly. By periodically removing the part to measure the diameter, in this way it is possible to obtain a surface with dimensional accuracy according to the second class.

Polishing.

For In order to polish any steel surface, prepare two wooden "kolobashki" (1) measuring 40x40 millimeters: one for rough and the second for fine polishing. Fix on them the angled tin plates (2) acting as a cathode so that their position can be adjusted in height. To debug the polishing process, you need to take a workpiece (3), connect it to the positive pole of the current source and place it in a bath with electrolyte so that the level of the solution lies slightly above the horizontal part of the cathode (2). Then the rough "kolobashka" should be dipped with one of the ends into the salt solution in the bath, removed and poured on it with a pinch of fine abrasive powder. Now, turning on the current, start polishing the part in a circular motion. In this case, it may happen that the electrochemical dissolution will be faster than the process of removing waste by the abrasive. To eliminate this discrepancy, raise the cathode plate higher and the dissolution rate will decrease. After polishing the entire surface with the first “bowl”, change the electrolyte solution to a clean one, wash the part from the abrasive and use the second “bowl” to start fine polishing, which should be carried out either without abrasive at all, or using tooth powder instead. With some training in this way, you can get a mirror surface on parts two to three times faster than mechanical polishing.

"Frost" on white plate.

Take empty tin can or just a piece of tinplate and connect to the wire from the positive pole of the rectifier. And connect any metal rod to the other pole, having previously made a cotton swab at its lower end. If now this kind of "shaving brush" is dipped into a solution of common salt and then slowly driven over the surface of the tin, then amazing things will happen to it. In those places where you brushed 2-3 times, sparkling crystals of "frost" appear - the crystalline structure of the tin coating will come to light. If you continue the process, then gray islands of waste will soon appear on the metal, firmly associated with the metal. And in the future, the entire surface of the tin will become spotty gray, with a characteristic bizarre pattern.
For To obtain various decorative patterns on metal, you can try using solutions of different salts or acids. So, for example, if instead of a solution of common salt we take a one percent solution of sulfuric acid, then the "appearing" crystals will acquire a brown tint. If a tin plate is sprinkled with toothpowder, then the “frost” pattern will become more contrasting, with a milky gray tint. By preheating individual parts of the tin piece until the tin is melted locally and quickly cooling them in water, it is possible to obtain the most intricate ornaments on metal. Such ornaments look especially good if they are covered with colored varnish on top. Try it and you will see that a lot of beautiful things can be made from a simple tin can.