The website outlines the basics of the technology galvanic coatings. The processes of preparation and application of electrochemical and chemical coatings, as well as methods for quality control of coatings. The main and auxiliary equipment galvanic workshop. Information is provided on mechanization and automation of galvanic production, as well as sanitation and safety precautions.

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, including important place protects metals from corrosion. Corrosion of metals, i.e. their destruction due to electrochemical or chemical exposure to the environment, causes enormous damage to the national economy. Every year, due to corrosion, up to 10-15% of the annual metal output in the form of valuable parts and structures, complex instruments and machines goes out of use. In some cases, corrosion leads to accidents.

Electroplating is one of the effective methods protection against corrosion, 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 appearance products.

Russian scientists are the creators of many important methods of electrochemical processing of metals. Thus, the creation of galvanoplasty is the merit of academician B. S. Jacobi (1837). Major works in the field of electroplating belong to the Russian scientists E. X. Lenz and I. M. Fedorovsky. Development of electroplating technology after October Revolution inextricably linked with names learned professors N. T. Kudryavtsev, V. I. Lainer, N. P. Fedotiev and many others.

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

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

Electrolytic chrome plating is in an efficient way increasing the wear resistance of rubbing parts, protecting them from corrosion, as well as a method of protective and decorative finishing. Significant savings come from chrome plating when restoring worn parts. The chrome plating process 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 appearing, and methods are being developed to increase mechanical properties chrome parts, as a result of which the scope of application of chrome plating expands. Knowledge of the basics of modern chrome plating technology contributes to the implementation of the instructions of regulatory and technical documentation and the creative participation of a wide range of practitioners in further development chrome plating

The site has developed issues of the influence of chrome plating on the strength of parts, expanded the use of effective electrolytes and technological processes, and introduced a new section on methods for increasing the efficiency of chrome plating. The main sections have been redesigned taking into account the advanced achievements of chrome plating technology. The given technological instructions and designs of hanging devices are exemplary, guiding the reader in matters of choosing chrome plating conditions and the principles of designing hanging devices.

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

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

Plastic parts with metal coatings widely used in the automotive industry, radio engineering industry and other sectors of the national economy. Especially great value metallization processes polymer materials purchased in production 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, and presents the basic principles of chemical deposition of metals. The features of electrolytic coatings for metallization of plastics are indicated. Considerable attention is paid to the production technology of printed circuit boards, and methods for analyzing solutions used in metallization processes, and methods for their preparation and correction are given.

In an accessible and fascinating form, the site introduces the physical nature in the features of ionizing radiation and radioactivity, the influence of various doses of radiation on living organisms, methods of protection and prevention of radiation hazards, the possibilities of using radioactive isotopes for recognizing and treating human diseases.

B. Rau

Processes Electrochemical metal processing is used in all industries. With their help, you can perform operations such as drilling, turning, grinding or polishing, milling parts of complex configurations, and even removing burrs. In this case, the essence of the processes of electrochemical dimensional processing is the anodic dissolution of the metal during electrolysis with regular removal of the resulting waste. And therefore - and this is the most valuable thing - there are practically no hard-to-cut metals for electrochemical “cutting” processes.
All These advantages of electrochemical processing processes can be successfully used at home to perform many interesting and useful works. For example, with their help you can cut an elastic plate from a razor blade in 20-30 minutes, cut a hole complex shape in a thin sheet of metal, carve a spiral-shaped groove on a round rod. To perform all these works, it is enough to have a rectifier AC, giving an output voltage of 6-10 volts, or a rectifier for 6-volt micromotors, 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 recess of a complex configuration - for example, cut out an apartment number - then to do this you need to take a sheet of Whatman paper and draw on it life size outline of the indentation you want to achieve. Then use a razor blade or scissors to 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 using 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 remaining surfaces 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 table salt, install a cathode plate (3) made 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 by a decrease in the number of bubbles released at the cathode (3). This means that an insulating layer of process waste has formed on the surface being treated. To remove them and at the same time measure the depth of the recess, the part must be removed from the glass and, being careful not to damage the mask template, use a small hard brush to clean off the loose layer of waste from the surface being treated. After this, periodically removing the part to control the dimensions and remove waste, the process can be continued until the excavation depth 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 you need to make a hole of a complex configuration; the principles of electrochemical processing remain the same as when milling. The only subtlety is that in order for the edges of the hole to be smooth, the mask template (1) must be glued to the workpiece on 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, gluing the template onto the workpiece (2), orient it along one of its sides. And in addition, 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 shape of the letter “U” and place the workpiece into it.
For Manufacturing parts of any profile from sheet steel - for example, from a razor blade - proceeds somewhat differently. The profile of the part itself (1) is cut out of paper and glued to the workpiece (2). Then the entire the opposite side steel sheet, and on the template side, varnish insulation is applied so that it does not adjoin the template. And only in one place should the applied insulation be brought to the template using a narrow bridge (3) - otherwise, the dissolution of non-insulated surfaces around the template may end before the outline of the part is formed. To obtain more precise parts, you can cut out two templates, stick them on the workpiece on both sides and carry out processing in a U-shaped cathode. Using similar methods, you can make various inscriptions on metal, both convex and “pressed.”

Threading and spiral grooving.

One One of the varieties of the milling process is electrochemical cutting of spiral grooves and threads. This method can be useful for making, for example, wood screws or twist drills at home. When cutting threads on a screw, as a template-mask (1), you need to take a thin rubber cord with a square section of 1x1 millimeter, wind it in a spiral with tension on a cylindrical workpiece (2) and secure its ends with threads (3). And then those surfaces of the workpiece that are not subject to etching are insulated with varnish. As a result of electrochemical processing, a spiral thread cavity is formed between the turns of rubber on the workpiece. Now you need to sharpen or, more precisely, make conical that end of the workpiece, which will serve as the tip of the screw entering the tree. To do this, you need to remove the workpiece from the bath, remove the rubber from it and dry it. And then, having varnished its surface so that only the first 2-3 threads of the thread remain open, the workpiece is returned to the bath and continued electrochemical processing some more time.
For To make a twist drill at home, as a template-mask (1), you need to take three rubber cords of the same cross-section and wind them onto a heat-treated cylindrical workpiece (2), but in two passes. Then the surfaces of the workpiece that are not to be processed, and for reliability, the rubber cords must be coated with varnish and, lowering the part into a glass bath, electrochemical milling of the drill grooves to the required depth. Now these grooves need to be expanded 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 time. After this, by removing the remaining insulation and sharpening the lead, you will have an excellent twist drill.

Grinding.

To To polish the surface of cylindrical parts using the electrochemical method, in addition to traditional equipment, you need to have a small electric motor or drill. Having previously insulated the surfaces of the part that are not to be treated with varnish, fasten it on the electric motor shaft (1), install the motor vertically on some bracket and lower the end of the part to be treated (2) into a bath of electrolyte. In this case, it is best to supply the anode part (2) with current using a sliding contact going to the motor shaft, and make the cathode (3) flat, equal in length to the surface being treated. Now all that remains is to turn on the electric motor and power to the bath. With the beginning of the process, the surface will begin to darken - the formation of waste. To get the correct cylindrical the surface being treated, this waste must be continuously removed. This can be conveniently done using a toothbrush with bristles shortened for rigidity, which, when pressed against the part, should be moved steadily up and down. By periodically removing the part to measure the diameter, in this way you can obtain a surface with dimensional accuracy of the second class.

Polishing.

For In order to polish any steel surface, prepare two wooden “bottles” (1) measuring 40x40 millimeters: one for roughing and the second for finishing polishing. Attach tin plates (2) bent at an angle to them, acting as a cathode, so that their position can be adjusted in height. To debug the polishing process, you need to take the workpiece (3), connect it to the positive pole of the current source and place it in a bath of electrolyte so that the level of the solution lies slightly above the horizontal part of the cathode (2). Then the rough “ball” should be dipped with one of the ends into the solution of table salt in the bath, taken out and a pinch of fine abrasive powder sprinkled on it. Now, turning on the current, begin polishing the part in a circular motion. In this case, it may happen that electrochemical dissolution will proceed faster than the process of removing waste with an abrasive. To eliminate this discrepancy, raise the cathode plate higher and the dissolution rate will decrease. Having polished the entire surface with the first “ball”, change the electrolyte solution to a clean one, wash the part from the abrasive and with the help of the second “roll” proceed to final polishing, which should be done either without any abrasive at all, or using tooth powder instead. With some training in this way you can get on the details mirror surface two to three times faster than mechanical polishing.

"Frost" on tinplate.

Take an empty 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 you now dip this kind of “brush” into a solution of table salt and then begin to slowly move it over the surface of the tin, then amazing things will happen to it. In those places where you swabbed 2-3 times, sparkling crystals of “frost” appear - the crystalline structure of the tin coating will be revealed. If you continue the process, gray islands of waste will soon appear on the metal, firmly bound to the metal. And in the future, the entire surface of the tin will become spotted 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 table salt you take a one percent solution of sulfuric acid, then the “developing” crystals will acquire a brown tint. If you sprinkle the tin plate with tooth powder, the “frost” pattern will become more contrasting, with a milky-gray tint. By preheating individual parts of a tin piece until the tin melts locally and quickly cooling them in water, one can 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 it is simple tin can you can do a lot of beautiful things.

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

In electrochemical milling, a protective coating can be made of any acid-resistant paint applied using a stencil. The etching 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 cathodes. After the process is terminated, the cathodes are removed from the bath.

Electrochemical milling differs in higher accuracy compared to chemical ones.

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 oxidizing aluminum, to achieve a shiny surface, mechanical polishing alone is not enough; after it, chemical or electrical polishing is necessary.

21. Solutions for pre-treatment aluminum

Orthophosphoric acid Ice acetic acid Orthophosphoric acid

280-290 15-30 1-6

Acid orange * To obtain:

dye 2

pinned surface

1st treatment with intermediate process

ratu-ra. WITH

4. ORTHOPHOSPHOR!

Triethane! lamin

500-IfXX) 250-550 30-80

Triethanolamine Catalin BPV

850-900 100-150

Orthops f mercury acids Chromic acid

* PS mining products are processed by washing in the same washing machine 6A/dm2

tro chemical polishing When polishing precious metals chemical or electrochemically their losses are completely eliminated. Electrochemical and chemical polishing can be not only a preparatory operation before electroplating, but also the final stage 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 deposit, 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, hydrogen released together with the metal, the electrolysis mode - temperature

ski polishing

M 41
with SS
Density
„|§..
Cathodes

From Slali
Carbon

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

1-5
10-100

Made of steel 12Х18Н97
H: rusting

From styles 12Х18Н9Т Aluminum and 3-5 20-50 - (aluminum) stainless

0.5-5.0 20-50 1.60-1.61 From copper or evin- Copper on it

temperature, hoc density, presence of swing, filtration, etc.

To improve the structure of the precipitate, various organic additives (glue, gelatin, saccharin, etc.) are introduced into the 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 fragility and porosity , and the appearance of so-called pitting points. To reduce the effect of hydrogen on the quality of the deposit, parts are shaken during the process, oxidizing agents are introduced, the temperature is increased, etc. The porosity of the deposit decreases with increasing thickness.

The uniform distribution of the deposit on the surface and the surface depends on the dissipating ability of the electrolyte. Alkaline and cyanide electrolytes have the best dissipating ability, acidic electrolytes have much less, and chromium electrolytes have the worst dissipating ability.

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

lntamn that do not require heating, ventilation, filtration; when coating products of complex shapes, solutions of complex metal salts should be used; for coating internal and hard-to-reach surfaces - internal and additional anodes, filtration, mixing; to receive shiny coating- electrolytes with complex shine-forming and leveling additives, etc.

GENERAL SCHEME OF THE TECHNOLOGICAL PROCESS

The coating process consists of a series of sequential operations - preparatory, coating and finishing. Preparatory operations include mechanical processing [of parts, degreasing in organic solvents, chemical or electrochemical degreasing, etching and polishing. Final coating processing includes dewatering, brightening, passivation, impregnation, polishing, and brushing. After each operation

Electrochemistry in a glass

Electrochemical metal processing processes are used in all industries. With their help, you can perform operations such as drilling, turning, grinding or polishing, milling parts of complex configurations, and even removing burrs. At the same time, the essence of the processes of electrochemical dimensional processing is the anodic dissolution of the metal during electrolysis with the regular removal of generated waste. And therefore - and this is the most valuable thing - there are practically no hard-to-cut metals for electrochemical “cutting” processes.

All these advantages of electrochemical processing processes can be successfully used at home to perform many interesting and useful jobs. For example, with their help you can cut an elastic plate from a razor blade in 20-30 minutes, cut a complex-shaped hole in a thin sheet of metal, and carve a spiral-shaped groove on a round rod (Fig. 1). To perform all this work, it is enough to have an AC rectifier that produces an output voltage of 6-10 volts, or a 6-volt rectifier for micromotors, 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 you need to make a recess of a complex configuration in some workpiece - for example, cut out an apartment number (Fig. 2) - then to do this you need to take a sheet of whatman paper and on it draw a life-size outline of the recess that you want to obtain. Then use a razor blade or scissors to 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 using 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 remaining surfaces 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 table salt, install a cathode plate (3) made of any metal opposite the mask template and connect it to the negative pole of the rectifier or current source.

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 by a decrease in the number of bubbles released at the cathode (3). This means that an insulating layer of process waste has formed on the surface being treated. To remove them and at the same time measure the depth of the recess, the part must be removed from the glass and, being careful not to damage the mask template, use a small hard brush to clean off the loose layer of waste from the surface being treated. After this, periodically removing the part to control the dimensions and remove waste, the process can be continued until the excavation depth 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 it is necessary to make a hole of a complex configuration in a thin sheet of metal, the principles of electrochemical processing remain the same as for milling. The only subtlety is that in order for the edges of the hole to be smooth, the mask template (1) must be glued to the workpiece on 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, gluing the template onto the workpiece (2), orient it along one of its sides (Fig. 3). And in addition, 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 shape of the letter “U” and place the workpiece into it.

To make parts of any profile from sheet steel - for example, from a razor blade - parts of any profile are done somewhat differently. The profile of the part itself (1) is cut out of paper and glued to the workpiece (2) (Fig. 4). Then the entire opposite side of the steel sheet is coated with varnish, and varnish insulation is applied on the template side so that it does not adjoin the template. And only in one place should the applied insulation be brought to the template using a narrow bridge (3) - otherwise, the dissolution of non-insulated surfaces around the template may end before the outline of the part is formed. To obtain more precise parts, you can cut out two templates, stick them on the workpiece on both sides and carry out processing in a U-shaped cathode. Using similar methods, you can make various inscriptions on metal, both convex and “pressed”.

Threading and spiral grooving.

One variation of the milling process is electrochemical cutting of spiral grooves and threads. This method can be useful for making, for example, wood screws or twist drills at home. When cutting a thread on a screw (Fig. 5), as a mask template (1), you need to take a thin rubber cord with a square section of 1x1 millimeter, wind it in a spiral with tension on a cylindrical workpiece (2) and secure its ends with threads (3). And then those surfaces of the workpiece that are not subject to etching are insulated with varnish. As a result of electrochemical processing, a spiral thread cavity is formed between the turns of rubber on the workpiece. Now you need to sharpen or, more precisely, make conical that end of the workpiece, which will serve as the tip of the screw entering the tree. To do this, you need to remove the workpiece from the bath, remove the rubber from it and dry it. And then, having varnished its surface so that only the first 2-3 threads remain open, the workpiece is returned to the bath and the electrochemical processing is continued for some more time.

To make a twist drill at home as a mask template (1), you need to take three rubber cords of the same cross-section and wind them onto a heat-treated cylindrical workpiece (2), but in two passes (Fig. 6). Then the surfaces of the workpiece that are not to be processed, and for reliability, the rubber cords must be varnished and, lowering the part into a glass bath, electrochemical milling of the drill grooves to the required depth. Now these grooves need to be expanded 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 time. After this, by removing the remaining insulation and sharpening the lead, you will have an excellent twist drill.

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

In electrochemical milling, a protective coating can be made of any acid-resistant paint applied using a stencil. The etching 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 cathodes. After the process is terminated, the cathodes are removed from the bath.

Electrochemical milling has higher accuracy compared to 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 oxidizing aluminum, to achieve a shiny surface, mechanical polishing alone is not enough; after it, chemical or electrical polishing is necessary.

21. Solutions for pre-treatment of aluminum

Orthophosphoric acid Ice acetic acid Orthophosphoric acid

280-290 15-30 1-6

Acid orange * To obtain:

dye 2

pinned surface

1st treatment with intermediate process

ratu-ra. WITH

4. ORTHOPHOSPHOR!

Triethane! lamin

500-IfXX) 250-550 30-80

Triethanolamine Catalin BPV

850-900 100-150

Orthops f mercury acids Chromic acid

* PS mining products are processed by washing in the same washing machine 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 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 deposit, 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, hydrogen released together with the metal, the electrolysis mode - temperature

ski polishing

M 41
with SS
Density
„|§..
Cathodes

From Slali
Carbon

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

1-5
10-100

Made of steel 12Х18Н97
H: rusting

From styles 12Х18Н9Т Aluminum and 3-5 20-50 - (aluminum) stainless

0.5-5.0 20-50 1.60-1.61 From copper or evin- Copper on it

temperature, hoc density, presence of swing, filtration, etc.

To improve the structure of the precipitate, various organic additives (glue, gelatin, saccharin, etc.) are introduced into the 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 fragility and porosity , and the appearance of so-called pitting points. To reduce the effect of hydrogen on the quality of the deposit, parts are shaken during the process, oxidizing agents are introduced, the temperature is increased, etc. The porosity of the deposit decreases with increasing thickness.

The uniform distribution of the deposit on the surface and the surface depends on the dissipating ability of the electrolyte. Alkaline and cyanide electrolytes have the best dissipating ability, acidic electrolytes have much less, and chromium electrolytes have the worst dissipating ability.

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

lntamn that do not require heating, ventilation, filtration; when coating products of complex shapes, 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 shiny coating - electrolytes with complex shine-forming and leveling additives, etc.

GENERAL SCHEME OF THE TECHNOLOGICAL PROCESS

The coating process consists of a series of sequential operations - preparatory, coating and finishing. Preparatory operations include mechanical processing of parts, degreasing in organic solvents, chemical or electrochemical degreasing, etching and polishing. Final coating processing includes dewatering, brightening, passivation, impregnation, polishing, and brushing. After each operation