Chrome plating or nickel plating how to distinguish in appearance. Nickel plating, chrome plating, bluing, etc.

16.06.2019

1. NICKEL PLATE. 2

2. CHROME PLATE. 6

LIST OF USED SOURCES.. 10

1. NICKEL PLATE

Nickel-plated coatings have a number of valuable properties: they are well polished, acquiring a beautiful long-lasting mirror finish, they are durable and well protect the metal from corrosion.

The color of nickel plating is silvery white with a yellowish tint; they are easily polished, but fade over time. The coatings are characterized by a fine-grained structure, good adhesion to steel and copper substrates, and the ability to passivate in air.

Nickel plating is widely used as a decorative coating for parts of lamps intended for lighting public and residential premises.

To cover steel products, nickel plating is often carried out over an intermediate copper sublayer. Sometimes a three-layer nickel-copper-nickel coating is used. In some cases, a thin layer of chromium is applied to the nickel layer, and a nickel-chromium coating is formed. On parts made of copper and alloys based on it, nickel is applied without an intermediate sublayer. The total thickness of two and three-layer coatings is regulated by mechanical engineering standards, usually it is 25–30 microns.

On parts intended for operation in a humid tropical climate, the coating thickness should be at least 45 microns. In this case, the regulated thickness of the nickel layer is not less than 12–25 µm.

To obtain brilliant coatings, nickel-plated parts are polished. Recently, brilliant nickel plating has been widely used, which eliminates the laborious operation of mechanical polishing. Brilliant nickel plating is achieved by introducing brighteners into the electrolyte. However, the decorative qualities of mechanically polished surfaces are higher than those obtained by bright nickel plating.

Nickel deposition occurs with significant cathodic polarization, which depends on the temperature of the electrolyte, its concentration, composition, and some other factors.

Electrolytes for nickel plating are relatively simple in composition. Currently, sulfate, hydroboric fluoride and sulfamic electrolytes are used. Lighting factories use exclusively sulfate electrolytes, which allow them to work with high current densities and at the same time obtain high-quality coatings. The composition of these electrolytes includes salts containing nickel, buffer compounds, stabilizers and salts that contribute to the dissolution of the anodes.

Sulfate electrolytes have high electrical conductivity and good dissipation ability.

An electrolyte of the following composition, g/l, has been widely used:

NiSO4 7H2O 240–250

*Or NiCl2 6H2O - 45 g/l.

Nickel plating is carried out at a temperature of 60°C, pH=5.6÷6.2 and a cathodic current density of 3–4 A/dm2.

Depending on the composition of the bath and its mode of operation, coatings with varying degrees of gloss can be obtained. For these purposes, several electrolytes have been developed, the compositions of which are given below, g/l:

for matte finish:

NiSO4 7H2O 180–200

Na2SO4 10H2O 80–100

Nickel plated at a temperature of 25–30°C, at a cathodic current density of 0.5–1.0 A/dm2 and pH=5.0÷5.5;

for a semi-gloss finish:

Nickel sulfate NiSO4 7H2O 200–300

Boric acid H3BO3 30

2,6–2,7-Disulfonaphthalic acid 5

Sodium fluoride NaF 5

Sodium chloride NaCl 7–10

Nickel plating is carried out at a temperature of 20–35°C, cathodic current density 1–2 A/dm2 and pH=5.5÷5.8;

for a shiny finish:

Nickel sulfate (hydrate) 260–300

Nickel chloride (hydrate) 40–60

Boric acid 30–35

Saccharin 0.8–1.5

1,4-butyndiol (in terms of 100%) 0.12-0.15

Phthalimide 0.08–0.1

Nickel plating operating temperature 50–60°C, electrolyte pH 3.5–5, cathodic current density with intensive stirring and continuous filtration 2–12 A/dm2, anode current density 1–2 A/dm2.

A feature of nickel plating is a narrow range of electrolyte acidity, current density and temperature.

To maintain the composition of the electrolyte within the required limits, buffer compounds are introduced into it, which are most often used as boric acid or a mixture boric acid with sodium fluoride. In some electrolytes, citric, tartaric, acetic acid or their alkaline salts are used as buffer compounds.

A feature of nickel coatings is their porosity. In some cases, dotted spots, the so-called "pitting", may appear on the surface.

To prevent pitting, intensive air mixing of the baths and shaking of the suspensions with parts attached to them are used. The reduction of pitting is facilitated by the introduction of surface tension reducers or wetting agents into the electrolyte, which are used as sodium lauryl sulfate, sodium alkyl sulfate and other sulfates.

The domestic industry produces a good anti-pitting detergent"Progress", which is added to the bath in the amount of 0.5 mg / l.

Nickel plating is very sensitive to impurities that enter the solution from the surface of parts or due to anodic dissolution. When nickel plating steel de-

hoists, the solution is clogged with iron impurities, and when coating copper-based alloys - with its impurities. Impurities are removed by alkalizing the solution with carbonate or nickel hydroxide.

Organic pitting contaminants are removed by boiling the solution. Sometimes nickel-plated parts are tinted. In this case, colored surfaces with a metallic sheen are obtained.

Toning is carried out by a chemical or electrochemical method. Its essence lies in the formation of a thin film on the surface of the nickel coating, in which light interference occurs. Such films are obtained by applying organic coatings several micrometers thick to nickel-plated surfaces, for which the parts are treated in special solutions.

Black nickel coatings have good decorative qualities. These coatings are obtained in electrolytes in which zinc sulfates are added in addition to nickel sulfates.

The composition of the electrolyte for black nickel plating is as follows, g/l:

Nickel sulfate 40–50

Zinc sulfate 20-30

Potassium thiocyanate 25–32

Ammonium sulphate 12–15

Nickel plating is carried out at a temperature of 18–35°C, cathodic current density of 0.1 A/dm2 and pH=5.0÷5.5.

2. CHROME PLATE

Chrome coatings have high hardness and wear resistance, low coefficient of friction, are resistant to mercury, adhere strongly to the base metal, and are chemically and heat resistant.

In the manufacture of lamps, chromium plating is used to obtain a protective decorative coatings, as well as reflective coatings in the manufacture of mirror reflectors.

Chrome plating is carried out on a pre-applied copper-nickel or nickel-copper-nickel sublayer. The thickness of the chromium layer with such a coating usually does not exceed 1 μm. In the manufacture of reflectors, chromium plating is currently being replaced by other coating methods, but in some factories it is still used for the manufacture of reflectors for mirrored lamps.

Chromium has good adhesion to nickel, copper, brass and other materials to be deposited, however, when other metals are deposited onto chromium, poor adhesion is always observed.

A positive feature of chromium coatings is that the parts are shiny directly in galvanic baths, this does not require them to be polished mechanically. Along with this, chromium plating differs from other galvanic processes by more stringent requirements for the operating mode of the baths. Minor deviations from the required current density, electrolyte temperature and other parameters inevitably lead to deterioration of coatings and mass rejects.

The scattering power of chromium electrolytes is low, resulting in poor coverage. internal surfaces and recessed parts. To improve the uniformity of coatings, special suspensions and additional screens are used.

For chromium plating, solutions of chromic anhydride with the addition of sulfuric acid are used.

Industrial Application found three types of electrolytes: diluted, universal and concentrated (Table 1). To obtain decorative coatings and to obtain reflectors, a concentrated electrolyte is used. In chromium plating, insoluble lead anodes are used.

Table 1 - Electrolyte compositions for chromium plating

During operation, the concentration of chromic anhydride in the baths decreases, therefore, to restore the baths, daily adjustments are made by adding fresh chromic anhydride to them.

Several formulations of self-regulating electrolytes have been developed, in which the concentration ratio is automatically stored.

The composition of such an electrolyte is as follows, g/l:

Chrome plating is carried out at a cathode current density of 50–80 A/dm2 and a temperature of 60–70°C.

Depending on the relationship between temperature and current density, one can obtain different kinds chrome coating: milky shiny and matte.

The milky coating is obtained at a temperature of 65–80 ° C and

low current density. A brilliant coating is obtained at a temperature of 45–60°C and an average current density. A matt finish is obtained at 25–45°C and high current density. In the production of fixtures, a shiny chrome coating is most often used.

To obtain mirror reflectors, chromium plating is carried out at a temperature of 50–55°C and a current density of 60 A/dm2. in the manufacture of mirror reflectors, copper and nickel are pre-deposited. The reflective surface is polished after applying each of the layers. Technological process includes the following operations:

grinding and polishing the surface;

copper plating;

nickel plating;

polishing, degreasing, pickling;

chrome plating;

clean polishing.

Products made of copper and copper alloys are chromium-plated without an intermediate sublayer. The parts are immersed in the electrolyte after voltage is applied to the bath. When applying multilayer coatings to steel products, the layer thickness is regulated by GOST 3002-70. Thickness values are given in table 2.

Table 2 - Minimum thickness of multilayer galvanized coatings

Chrome plating baths are equipped with a powerful exhaust ventilation to remove fumes of poisonous chromic acid.

During chromium plating, part of the hexavalent Cr6+ chromium enters wastewater, therefore, to prevent Cr6+ emissions into open water bodies, protective measures- install neutralizers and treatment facilities.

LIST OF USED SOURCES

1. Afanas'eva E.I., Skobelev V.M. "Light sources and ballasts: Textbook for technical schools", 2nd ed., Rev., M: Energoatomizdat, 1986, 270s.

2. Bolenok V.E. "Production of electric lighting devices: Textbook for technical schools", M: Energoizdat, 1981, 303s.

3. Denisov V.P. "Production of electric light sources", M: Energy, 1975, 488s.

4. Denisov V.P., Melnikov Yu.F. "Technology and equipment for the production of electric light sources: Textbook for technical schools", M: Energy, 1983, 384s.

5. Plyaskin P.V. etc. "Fundamentals of designing electrical light sources", M: Energoatomizdat, 1983, 360s.

6. Churkina N.I., Lityushkin V.V., Sivko A.P. "Fundamentals of technology of electric light sources" / ed. ed. Prytkova A.A., Saransk: Mordovian book publishing house, 2003, 344p.

PLAN 1. NICKEL PLATE 2. CHROME PLATE 6 LIST OF SOURCES USED 1. NICKEL PLATE Nickel coatings have a number of valuable properties: they are well polished, acquiring a beautiful long-lasting mirror shine, they are resistant and well protect the metal from corrosion. The color of nickel plating is silvery white with a yellowish tint; they are easily polished, but fade over time. The coatings are characterized by a fine crystalline structure, good adhesion to steel and copper substrates and the ability to passivate in air.

Nickel plating is widely used as a decorative coating for parts of lamps intended for lighting public and residential premises. To cover steel products, nickel plating is often carried out over an intermediate copper sublayer. Sometimes a three-layer nickel-copper-nickel coating is used. In some cases, a thin layer of chromium is applied to the nickel layer, and a nickel-chromium coating is formed. On parts made of copper and alloys based on it, nickel is applied without an intermediate sublayer.

The total thickness of two and three-layer coatings is regulated by mechanical engineering standards, usually it is 25–30 microns. On parts intended for operation in a humid tropical climate, the coating thickness should be at least 45 microns. In this case, the regulated thickness of the nickel layer is not less than 12–25 µm. To obtain brilliant coatings, nickel-plated parts are polished.

Recently, brilliant nickel plating has been widely used, which eliminates the laborious operation of mechanical polishing. Brilliant nickel plating is achieved by introducing brighteners into the electrolyte. However, the decorative qualities of mechanically polished surfaces are higher than those obtained by bright nickel plating. Nickel deposition occurs with significant cathodic polarization, which depends on the temperature of the electrolyte, its concentration, composition, and some other factors.

The advantages of these electrolytes are the lack of components, high stability and low aggressiveness. Electrolytes allow a high concentration of nickel salt in their composition, which makes it possible to increase the cathode current density and, consequently, to increase the productivity of the process. Sulfate electrolytes have high electrical conductivity and good dissipation ability. An electrolyte of the following composition, g/l, was widely used: NiSO4 7H2O 240–250 NaCl* 22.5 H3BO3 30 * Or NiCl2 6H2O - 45 g/l. Nickel plating is carried out at a temperature of 60°C, pH=5.6÷6.2 and a cathodic current density of 3–4 A/dm2. Depending on the composition of the bath and its mode of operation, coatings with varying degrees of gloss can be obtained.

For these purposes, several electrolytes have been developed, the compositions of which are given below, g/l: for a matte coating: NiSO4 7H2O 180–200 Na2SO4 10H2O 80–100 H3BO3 30–35 NaCl 5–7 Nickel plated at a temperature of 25–30°C, at cathodic density current 0.5–1.0 A/dm2 and pH=5.0÷5.5; for semi-bright coating: Nickel sulphate NiSO4 7H2O 200–300 Boric acid H3BO3 30 2,6–2,7-Disulfonaphthalic acid 5 Sodium fluoride NaF 5 Sodium chloride NaCl 7–10 Nickel plating is carried out at a temperature of 20–35°C, cathodic current density 1 –2 A/dm2 and pH=5.5÷5.8; for a shiny coating: Nickel sulfate (hydrate) 260-300 Nickel chloride (hydrate) 40-60 Boric acid 30-35 Saccharin 0.8-1.5 1.4-butyndiol (in terms of 100%) 0.12-0 .15 Phthalimide 0.08–0.1 Nickel plating operating temperature 50–60°C, electrolyte pH 3.5–5, cathode current density with intensive stirring and continuous filtration 2–12 A/dm2, anode current density 1–2 A /dm2. A feature of nickel plating is a narrow range of electrolyte acidity, current density and temperature. To maintain the composition of the electrolyte within the required limits, buffer compounds are introduced into it, which are most often used as boric acid or a mixture of boric acid with sodium fluoride.

In some electrolytes, citric, tartaric, acetic acid or their alkaline salts are used as buffer compounds. A feature of nickel coatings is their porosity.

In some cases, dotted spots, the so-called "pitting", may appear on the surface. To prevent pitting, intensive air mixing of the baths and shaking of the suspensions with parts attached to them are used.

The reduction of pitting is facilitated by the introduction of surface tension reducers or wetting agents into the electrolyte, which are used as sodium lauryl sulfate, sodium alkyl sulfate and other sulfates.

The domestic industry produces a good anti-pitting detergent "Progress", which is added to the bath in an amount of 0.5 mg / l. Nickel plating is very sensitive to impurities that enter the solution from the surface of parts or due to anodic dissolution.

When nickel-plating steel parts, the solution is clogged with iron impurities, and when copper-based alloys are coated with its impurities. Impurities are removed by alkalizing the solution with carbonate or nickel hydroxide. Organic pitting contaminants are removed by boiling the solution.

Sometimes nickel-plated parts are tinted. In this case, colored surfaces with a metallic sheen are obtained. Toning is carried out by a chemical or electrochemical method. Its essence lies in the formation of a thin film on the surface of the nickel coating, in which light interference occurs. Such films are obtained by applying organic coatings several micrometers thick to nickel-plated surfaces, for which the parts are treated in special solutions.

Black nickel coatings have good decorative qualities. These coatings are obtained in electrolytes in which zinc sulfates are added in addition to nickel sulfates. The composition of the electrolyte for black nickel plating is as follows, g/l: Nickel sulfate 40–50 Zinc sulfate 20–30 Potassium thiocyanate 25–32 Ammonium sulphate 12–15 Nickel plating is carried out at a temperature of 18–35°C, cathodic current density 0.1 A/dm2 and pH=5.0÷5.5. 2. CHROMIING Chrome coatings have high hardness and wear resistance, low coefficient of friction, are resistant to mercury, adhere strongly to the base metal, and are chemically and heat resistant.

In the manufacture of lamps, chromium plating is used to obtain protective and decorative coatings, as well as reflective coatings in the manufacture of mirror reflectors. Chrome plating is carried out on a pre-applied copper-nickel or nickel-copper-nickel sublayer. The thickness of the chromium layer with such a coating usually does not exceed 1 μm. In the manufacture of reflectors, chromium plating is currently being replaced by other coating methods, but in some factories it is still used for the manufacture of reflectors for mirrored lamps.

Chromium has good adhesion to nickel, copper, brass and other materials to be deposited, however, when other metals are deposited onto chromium, poor adhesion is always observed. A positive feature of chromium coatings is that the parts are shiny directly in galvanic baths, this does not require them to be polished mechanically.

Along with this, chromium plating differs from other galvanic processes by more stringent requirements for the operating mode of the baths. Minor deviations from the required current density, electrolyte temperature and other parameters inevitably lead to deterioration of coatings and mass rejects. The scattering power of chromium electrolytes is low, which leads to poor coating of internal surfaces and recesses of parts.

To improve the uniformity of coatings, special suspensions and additional screens are used. For chromium plating, solutions of chromic anhydride with the addition of sulfuric acid are used. Three types of electrolytes have found industrial application: diluted, universal and concentrated (Table 1). To obtain decorative coatings and to obtain reflectors, a concentrated electrolyte is used. In chromium plating, insoluble lead anodes are used. Table 1 – Electrolyte compositions for chromium plating components electrolyte compositions, g/l of dilute universal concentrated chromic anhydride sulfuric acid cathode current density, A/dm2 solution temperature, °С 150 1.5 45–100 55–60 250 2.5 15–60 45–55 350 3.5 10–30 35–45 During operation, the concentration of chromic anhydride in the baths decreases, therefore, to restore the baths, daily adjustments are made by adding fresh chromic anhydride to them. Several formulations of self-regulating electrolytes have been developed in which the concentration ratio is automatically maintained. The composition of such an electrolyte is as follows, g/l: Cr2O3 250 SrSO4 5-6 K2SiF6 20 Chromium plating is carried out at a cathode current density of 50–80 A/dm2 and a temperature of 60–70°C. Depending on the relationship between temperature and current density, different types of chromium coating can be obtained: milky shiny and matte. The milky coating is obtained at a temperature of 65–80°C and a low current density. A brilliant coating is obtained at a temperature of 45–60°C and an average current density. A matt finish is obtained at 25–45°C and high current density. In the production of fixtures, a shiny chrome coating is most often used.

The reflective surface is polished after applying each of the layers.

The technological process includes the following operations: grinding and polishing of the surface; copper plating; polishing, degreasing, pickling; nickel plating; polishing, degreasing, pickling; chrome plating; clean polishing.

After each technological operation, a 100% quality control of the coating is carried out, since non-compliance with the requirements of the technology leads to peeling of the sublayer along with the chromium coating. Products made of copper and copper alloys are chromium-plated without an intermediate sublayer.

The parts are immersed in the electrolyte after voltage is applied to the bath. When applying multilayer coatings to steel products, the layer thickness is regulated by GOST 3002-70. Thickness values are given in table 2. Table 2 - Minimum thickness of multilayer electroplated coatings operating conditions symbol coating groups coating thickness, microns ,5 Chrome plating baths are equipped with powerful exhaust ventilation to remove poisonous chromic acid vapors.

During chromium plating, part of the hexavalent chromium Cr6+ gets into wastewater, therefore, to prevent Cr6+ emissions into open water, protective measures are used - neutralizers and treatment facilities are installed.

2. 3. "Technology and equipment for the production of electric light sources ... and others. 6.

What will we do with the received material:

If this material turned out to be useful to you, you can save it to your page on social networks:

PLAN

1. NICKEL PLATE

2. CHROME PLATE

LIST OF USED SOURCES

1. NICKEL PLATE

Nickel-plated coatings have a number of valuable properties: they are well polished, acquiring a beautiful long-lasting mirror finish, they are durable and well protect the metal from corrosion.

Nickel plating is widely used as a decorative coating for parts of lamps intended for lighting public and residential premises.

Nickel deposition occurs with significant cathodic polarization, which depends on the temperature of the electrolyte, its concentration, composition, and some other factors.

Sulfate electrolytes have high electrical conductivity and good dissipation ability.

An electrolyte of the following composition, g/l, has been widely used:

NiSO4 7H2O 240–250

*Or NiCl2 6H2O - 45 g/l.

Nickel plating is carried out at a temperature of 60°C, pH=5.6÷6.2 and a cathodic current density of 3–4 A/dm2.

for matte finish:

NiSO4 7H2O 180–200

Na2SO4 10H2O 80–100

Nickel plated at a temperature of 25–30°C, at a cathodic current density of 0.5–1.0 A/dm2 and pH=5.0÷5.5;

for a semi-gloss finish:

Nickel sulfate NiSO4 7H2O 200–300

Boric acid H3BO3 30

2,6–2,7-Disulfonaphthalic acid 5

Sodium fluoride NaF 5

Sodium chloride NaCl 7–10

Nickel plating is carried out at a temperature of 20–35°C, cathodic current density 1–2 A/dm2 and pH=5.5÷5.8;

for a shiny finish:

Nickel sulfate (hydrate) 260–300

Nickel chloride (hydrate) 40–60

Boric acid 30–35

Saccharin 0.8–1.5

1,4-butyndiol (in terms of 100%) 0.12-0.15

Phthalimide 0.08–0.1

Nickel plating operating temperature 50–60°C, electrolyte pH 3.5–5, cathodic current density with intensive stirring and continuous filtration 2–12 A/dm2, anode current density 1–2 A/dm2.

A feature of nickel plating is a narrow range of electrolyte acidity, current density and temperature.

To maintain the composition of the electrolyte within the required limits, buffer compounds are introduced into it, which are most often used as boric acid or a mixture of boric acid with sodium fluoride. In some electrolytes, citric, tartaric, acetic acid or their alkaline salts are used as buffer compounds.

A feature of nickel coatings is their porosity. In some cases, dotted spots, the so-called "pitting", may appear on the surface.

The domestic industry produces a good anti-pitting detergent "Progress", which is added to the bath in an amount of 0.5 mg / l.

Nickel plating is very sensitive to impurities that enter the solution from the surface of parts or due to anodic dissolution. When nickel plating steel de-

hoists, the solution is clogged with iron impurities, and when coating copper-based alloys - with its impurities. Impurities are removed by alkalizing the solution with carbonate or nickel hydroxide.

Organic pitting contaminants are removed by boiling the solution. Sometimes nickel-plated parts are tinted. In this case, colored surfaces with a metallic sheen are obtained.

Black nickel coatings have good decorative qualities. These coatings are obtained in electrolytes in which zinc sulfates are added in addition to nickel sulfates.

The composition of the electrolyte for black nickel plating is as follows, g/l:

Nickel sulfate 40–50

Zinc sulfate 20-30

Potassium thiocyanate 25–32

Ammonium sulphate 12–15

Nickel plating is carried out at a temperature of 18–35°C, cathodic current density of 0.1 A/dm2 and pH=5.0÷5.5.

2. CHROME PLATE

Chrome coatings have high hardness and wear resistance, low coefficient of friction, are resistant to mercury, adhere strongly to the base metal, and are chemically and heat resistant.

Chrome plating is an electrolytic coating with chromium, despite the harmfulness of production, it is one of the most common types of coatings. When covering any part of a motorcycle or car, it becomes much more attractive in appearance and richer. And any chopper, classic or retro car, after chrome coating of its parts, literally transforms and attracts the eye. In this article, we will consider whether chromium plating, copper plating or nickel plating is possible at home, what types of chromium plating are and how they differ, we will consider both chemical and electroplated chromium plating (as well as modern method spraying), coating parts with nickel and copper, as well as the composition of various electrolytes and features of work.

Many people know that the chrome coating has not only a decorative function, but also many others. useful properties. These are corrosion resistance, both at normal and elevated temperatures, high hardness with a low coefficient of friction, resistance to mechanical wear, and a high light reflection coefficient, which is very useful when covering, for example, headlight reflectors.

In general, chromium coating can be divided into two groups: 1 - decorative and 2 - functional chromium plating.

Decorative chromium coating is widely used in the motorcycle and automotive industries, and in many other areas of technology, in which high demands are placed on both the aesthetic appearance of products and corrosion resistance. The decorative coating is applied in very thin layers (less than 1 µm) on intermediate layers, but the volume is lower.

Functional chromium coating is used mainly for coating tools (often measuring), templates, various forms for casting parts under pressure, and for coating other parts that are subject to mechanical wear.

Functional chromium coating is also very useful in restoring the original size of worn parts and machines. Functional coatings can be applied directly to steel or other substrates. and thickness functional coatings can reach several millimeters (especially when restoring worn parts).

Chrome has the property of being covered with a transparent and dense film (passive film), which increases resistance to corrosion and prevents darkening of shiny decorative coatings. But it should be noted that chromium itself is not able to create good anti-corrosion protection. And that is why, before applying chromium, it is important to cover the part with intermediate layers, such as nickel, and even better copper, then nickel.

To apply layers of copper, nickel and chromium to the surface of parts, there are several ways. The first one is electroplating coatings, the second is chemical coating, and the third method, which has appeared recently, is spray coating. We will consider each of these methods below, and which one is preferable, each master decides for himself, based on the conditions and possibilities.

Galvanic coating.

Galvanic method of application various coatings, despite the most high costs production and harmfulness, has the main advantage over other methods - it is the ability to apply a strong film of great thickness, which means it allows you to restore almost any worn part.

Moreover, the restored part will be more wear-resistant than the new one, and its resource will increase. This is very important property useful for example when restoring rare antique motorcycles or cars for which to buy new part, instead of worn out, is not so simple.

With the galvanic method of applying metal coatings, it is required to make special galvanic baths in which special substances are dissolved according to certain recipes (which are discussed below). And the amount of substances in these recipes corresponds to their content in one liter of the prepared solution.

Even for the electrolytic deposition of metals on parts, you will need a powerful DC source that will be capable of delivering a sufficiently large current at a low voltage (from 2 to 12 volts) - more than a hundred amperes. But for coating small parts (small things), a not very powerful power source is enough, even a rechargeable battery is suitable. It all depends on the size of the part and the smaller it is, the less current will be required (the same with the size of the bath, but more on that below).

You will also need a rheostat to adjust electric current in the anode circuit (the anode circuit is connected to the plus of the current source). An ammeter should be connected in series to the same electrical circuit to control the current strength. In addition, it will also be necessary to control the desired acidity of the electrolyte, which is determined by measuring the concentration of hydrogen ions (pH).

This indicator is determined using an electronic device "pH - meter", in which the pH value is shown on the scale, and in more modern devices on the display. Who does not have such a device, then you can look for a special indicator paper in the store, which is immersed in an electrolyte solution, and by changing its color shows the pH value.

Used to isolate metallic coatings special baths, or vessels (depending on the shape and dimensions of the parts). Small parts can be coated with metals in porcelain or glass jars (bowls). To cover larger parts, special baths are used, often made of steel sheet that are lined various materials. The lining material of the baths depends on the composition of the electrolyte and the required operating temperatures. But most often use sheet rubber.

Details must be sanded and polished to mirror shine, otherwise any scratch will be visible after applying copper, nickel, chrome. Rust is also removed from parts, and this can be done both mechanically (with steel brushes) and chemically.

Further, the parts are degreased chemically or electrolytically and thoroughly washed with running water. And only after that, the parts are suspended in the bath, that is, they are connected to the negative pole (minus the power source) and are the cathode. Most often, parts are suspended on copper wire, or on special hangers designed for several parts.

An anode in the form of a plate is connected to the positive pole (plus) and suspended on a wire in the bath. The plate is in most cases made of the same metal with which the part is to be coated. But in rare cases, when a part needs to be coated with some kind of rare metal, insoluble anodes made of platinum, stainless steel and even graphite are used. Periodically, the anodes should be removed from the bath and cleaned with a brush in a jet of water, from sediments deposited on them.

Security measures.

When working with galvanic baths, a number of conditions must be observed so that later you do not walk with ruined health. For electroplating use separate room, otherwise the tools in your workshop will rust pretty quickly.

And the first thing that will need to be done in this room, and right above the galvanic bath, is a forced exhaust. Hood 0 is the first and important condition that you should spend money on. It should also be taken into account that in many countries, after the hood, there must be special filters, otherwise such production will simply not be allowed to work.

Exhaust ventilation is simply necessary and should be installed directly above the bath, since even baths that are not energized, but at operating temperature, emit fumes harmful to the human body.

It should also be borne in mind that most electrolytes consist of highly caustic substances (alkali, acid), so be sure to work with rubber gloves, a rubber apron, and if there are several large bathtubs in the workshop, then it will not interfere with rubber boots. And when transfusing electrolytes, or filtering it, preparing it, etc., you should wear a protective face mask.

It should be remembered that some bath substances are dangerous poisons (mercury compounds, cyanides, antimony, arsenic). Therefore, you need to work with them very carefully and store such substances in a separate place (preferably in a safe). In general, in order to open production in many countries and work with such substances, qualified persons are needed who have permission to work with poisons.

If some people are stopped by what is written above, then you should choose other methods of chrome plating, that is, skip a few paragraphs and go down below to read about them. If you need to use the galvanic method, which allows you to get the thickest and most durable coatings - the so-called real chrome (or restore the size of a worn part), then read on.

Copper plating by galvanic method.

The composition at number 1 in the table, it is recommended to mix, and it is intended for matte copper plating (current efficiency is 95 - 98 percent).
Solution number 2 is better suited for bright copper plating, and it does not need to be stirred during the process.
Electrolyte solution number 3 is more suitable for fast copper plating, but it is recommended to mix it.
Well, solution number 4 is used to obtain shiny and smooth coatings, because it contains a gloss-forming and leveling additive. In addition, copper coated in this electrolyte has good ductility and low internal stresses.

It should only be taken into account that when preparing electrolyte number 4, the chemical purity of all components of the composition is required, and the presence of sodium chloride, which is added to distilled water, on the basis of which the electrolyte is prepared. And if you constantly mix the composition, then the current density in such an electrolyte can be increased to three or four amperes per square decimeter of the volume of the composition.

For direct coating of steel (and zinc), cyanide compounds are used, which, despite toxicity, are widely used. Moreover, copper is deposited very quickly when using them (and in solutions with a high concentration of copper, a high current density is allowed).

To cover steel and zinc alloys with copper, a fairly simple electrolyte composition is widely used, consisting of only two components: free sodium cyanide 10-20 (grams per liter), and copper cyanide (cyanide salt) - 40-50 g.l. The working temperature of the solution is 15 - 25 degrees, and the current density is approximately 0.5 - 1 ampere per square decimeter; current output 50 - 70%.

Other cyanide electrolytes differ only in various additives that slightly speed up the copper deposition process, or improve appearance coatings. For example, if you add 50-70 grams per liter of potassium-sodium tartrate (Rochelle salt), then the passive film on the anodes will dissolve during the coating process.

If there is a desire to most fully replace toxic and harmful cyanide solutions, then an electrolyte based on potassium ferricyanide and Rochelle salt can be used. The exact composition of the electrolyte is as follows: copper 20-25 grams per liter, ferrous-cyanogen potassium 180-220 gl, Rochelle salt 90-110 gl, caustic potash 8-10. Wherein working temperature the solution should be within 50-60 degrees, the current density is 1.5 - 2 amperes per square decimeter, the current output is 50 - 60%.

Instead of cyanide electrolytes, you can still use an electrolyte consisting of phosphoric acid, with a concentration of 250 - 300 grams per liter. Anodizing is carried out at room temperature and at a current density of 2 to 4 amperes per dm², with an average holding time of 10 minutes.

After that, the parts are washed in water and hung under current in any of the copper sulfate electrolytes, and then the specified thickness of the copper layer is increased. For whom all this is complicated, then you can cover the part with copper more in a simple way, described .

Nickel plating.

As I wrote above, before chrome plating, you need to apply a layer of copper to the part, then nickel and only then chromium. Therefore, nickel plating should also be described in detail, like copper plating and chromium plating. In addition, nickel plating is the most popular electroplating process.

And nickel-plated parts on custom and hot rods serve as a kind of fashionable style solution. After all, nickel-plated parts have an attractive appearance, sufficiently high corrosion resistance and good mechanical properties.

But it should be noted that nickel, which is applied directly to bare steel, is a cathodic coating, and therefore protects it from corrosion only mechanically. And the porosity of the nickel coating contributes to the formation of corrosive pairs in which steel is a soluble electrode.

This causes corrosion under the coating, which destroys the steel base and contributes to the peeling of the nickel film. To eliminate the troubles described above, the steel must first either be coated with copper, or coated with bare steel with a dense and thick layer of nickel (and without pores).

Nickel, like chromium, due to its high mechanical properties, is used to restore worn parts of engines and other units of machines and mechanisms. Moreover, in chemical industry a thick layer of nickel covers parts that are exposed to strong alkalis (for example, alkaline battery cases).

The cost of reagents together with a gun is approximately 380 - 400 euros. A portable sprayer can cost around 1,700 euros. But professional installations(with large volumes) can cost around 4000 euros, and some are even more expensive (for example, the Devil unit costs 5000 euros - shown in the photo on the left).

In addition, professional units can be equipped with a double gun (385 euros) as in the photo, which is more economical.

In general, it is unrealistic to describe such installations in detail within one article, and interested people can go to special sites selling such equipment and get acquainted in detail with many models and their prices. In addition, the technical process is developing every day, and every month something new and more perfect appears.

That seems to be all. I hope this article will be useful to someone, and everyone will choose for themselves the method of chrome plating of parts that is most suitable for their capabilities and their workshop, good luck to everyone.