Chemical plating and chrome plating at home. We chrome some elements of the car

Chromium-coated elements are typically used to improve the design of cars and motorcycles. The cost of such parts made under production conditions is quite high, and meanwhile, chrome plating at home is quite possible. By applying chrome to the surface of various products with your own hands, you can save significant financial resources.

Interest in doing chrome plating of various parts with their own hands at home is shown by many craftsmen who are not indifferent appearance them vehicle. In the technology of chrome plating at home, many nuances can be distinguished. In addition, it requires strict adherence to the sequence of all its stages.

Preparation for the procedure

To perform chrome plating at home, you need to do some preparation. First of all, you should choose the right room (preferably non-residential). In addition, before performing chrome plating, it is necessary to:

ensure ventilation of the room in which the technological operation will be performed (it is desirable that such ventilation is not natural, but forced);
find personal safety equipment (respirator, goggles, tight rubber gloves and apron)
decide how waste from the process will be disposed of.

Design of a chrome plating plant

For chrome plating at home, you can make a device consisting of the following elements:

a container in which a container for chrome plating will be installed;
the container itself, which can be used glass jar volume of 3 liters;
a wooden box with insulated walls, which contributes to the high-quality flow of the electrolysis process (fiberglass, sand, mineral wool or glass wool)
heating element, in the role of which an ordinary heating element of the corresponding power can act;
a device with which you can measure the temperature (it is best to use a contact thermometer, which allows you to automate technological process);
sealing cap, which is best made from wood board or moisture resistant plywood;
wires with which the workpiece is connected to the negative contact of the electric current source, and the anode, also immersed in the electrolytic solution, to the positive (the wire connected to the workpiece is best equipped with a crocodile clip: in this case it will be connected much more convenient).

You must also include a special bracket for hanging the workpiece in the electrolyte in your kit for chrome plating. It is necessary to use such a bracket so that the surface of the product is covered with a layer of chromium evenly from all sides.

Power Supply Requirements

Coating the surface of products with a layer of chromium, including chrome plating of parts at home, involves the use of a source direct current. Wiring diagram homemade device for chrome plating must meet the following requirements.

The current source that is equipped with a chrome plating kit must be able to adjust the output voltage. In the simplest version, a conventional rheostat can be used as such an adjusting device.
The cross section of the wires, with the help of which the anode and cathode are connected to the current source, is selected according to the maximum current strength. So, the equipment used for chrome plating of products small size, must be equipped with wires with a cross section of at least 2.5 mm 2.
If a household appliance for chrome plating involves the use of not an ordinary thermometer, but a thermostat, then for the correct use of such measuring device you need to assemble the appropriate electronic circuit.

The composition of the electrolyte and the rules for its preparation

In the event that you decide to apply a layer of chromium on the surface of the product with your own hands, it is important not only to assemble the appropriate equipment, but also to properly prepare the electrolytic solution. The composition of such a solution for chromium plating of metal includes the following components:

chromic anhydride (CrO 3) - 250 g / l;
sulfuric acid (H 2 SO 4) - 2.5 g / l.

These components are mixed with water.

After mixing with a hydrometer, check the density of the solution, which can be used to judge the content of chromic anhydride

Exist certain rules preparation of an electrolytic solution, which are as follows.

The container in which the electrolyte is prepared is half filled with water. In the event that not distilled, but ordinary water is used, it should be boiled and allowed to settle. The temperature of the water to which the remaining components are added should be about 60 °.
After the water is prepared and heated to the required temperature, chromic anhydride is poured into it and the resulting mixture is stirred until it is completely dissolved.
If the volume of the solution has decreased, it is necessary to add water to it.
Sulfuric acid is poured into the resulting solution. It should be borne in mind that the above values of the H 2 SO 4 content in the solution are relevant for an acid with specific gravity 1,84.
After the electrolyte is ready, it must be "worked out". Through it for 3.5 hours is passed electricity, the strength of which is calculated according to the following formula: 6.5 A for each liter of solution. Knowing specifications current source used, you can easily determine the required volume of electrolyte. If all the steps for "working out" the electrolytic solution are performed correctly, then its color will change to dark brown.
The electrolytic solution, with the help of which do-it-yourself chrome plating of parts will be performed, must be allowed to settle in a cool room for a day.

How to prepare a workpiece

The quality and durability of the coating applied to it depend on how correctly and carefully the chrome-plated surface is prepared. While the finished electrolytic solution is settling, you can start preparing the product, which consists in performing a certain list of actions.

cleaning

In the cleaning process, not only traces of dirt are removed from the part processed before chrome plating, but also residues old paint, rust, and any other foreign layers. The tools and fixtures used for cleaning are selected depending on how heavily soiled the surface is. To perform such a procedure, in particular, it can be used as usual sandpaper as well as a grinder.

Degreasing

The technology of chromium plating in production or at home involves the obligatory degreasing of the treated surface. The characteristics of the applied chromium coating also depend on the quality of this procedure.

For degreasing, as a rule, it is prepared special solution, which allows you to perform this procedure with the highest quality. The most popular of these aqueous solutions includes the following components:

sodium hydroxide - 150 g / l;
silicate glue - 5 g / l;
soda ash– 50 g/l.

The solution is heated to a temperature of 80–90 ° and the product is kept in it for 20 minutes. If the surface of the workpiece is highly complex or heavily soiled, the soak time in the degreasing solution can be extended up to 1 hour.

How is chrome plating

After everything preparatory work completed, a natural question arises: how to chrome a part correctly? First of all, it is necessary to heat the electrolytic solution to the required temperature (53 ± 2°) and maintain it throughout the entire processing process. After that, the product is placed in the electrolyte, which should already contain the anode. After some time, during which the temperature of the product becomes equal to the temperature of the electrolytic solution, an electric voltage is applied to the anode and the product.

After the completion of chromium plating, the product is removed from the electrolyte and placed in a heating furnace, where it is subjected to heat treatment for 2.5 hours. This is necessary in order not only to improve the adhesion of the chromium layer to the surface of the base metal, but also to increase the hardness of the coating.

In order to perform decorative chromium plating with the highest quality, it is important to study the theoretical material and learn the features of such a process (for example, from a video), as well as take a responsible approach to all stages of preparing the part and the electrolytic solution.

It is best to perform chromium plating of a prototype before processing the product in order to work out all the nuances of the technological process.

Chrome plating defects and their causes

When doing do-it-yourself chrome plating, many home craftsmen face the most typical defects applied coating, which can occur for various reasons.

1. There is a sheen on the coating, but it is uneven.

The current supplied to the product and the anode is too high.
The temperature of the electrolytic solution is not brought to the required value.

2. There is no gloss on the applied coating at all.

There is too much or not enough chromic anhydride in the electrolytic solution.
Operating current rating exceeded.
The amount of sulfuric acid in the solution is insufficient.

3. Brown spots appeared on the chrome surface.

The amount of chromic anhydride in the electrolytic solution is exceeded.
There is not enough sulfuric acid in the chromium plating solution.

4. Small shells are visible on the applied coating.

The treated surface was not well prepared.
When processed in solution, hydrogen is not removed from the surface. To solve this problem, it is necessary to change the layout of the product in the solution and the method of its subsequent drying.

5. Chrome plating is uneven.

Operating current is exceeded.

6. The applied coating is too soft.

The operating current is underestimated.
The temperature of the electrolytic solution is higher than the required value.

7. The applied coating peels off.

The voltage applied to the anode and cathode is unstable.
The surface of the workpiece was not sufficiently well degreased.
The temperature of the electrolyte during processing decreased.

Thus, in order to apply a layer of chromium on products with your own hands, it is not enough just to assemble your electroplating apparatus and study the theoretical base, it is also important to take into account many nuances that directly affect the quality finished coating. Therefore, it is important to know not only how to perform chrome plating, but also how to make sure that the chrome coating being formed is of guaranteed quality.

Chrome plating of parts is a process of plating with chromium in order to give the surface physical, mechanical and chemical properties and characteristics that differ from the original material of the part. Chrome plating is used to improve corrosion resistance, erosion resistance, mechanical resistance, decorative finishes and others.

Chrome plating process

Methods for applying a layer of chromium to the surface of the metallized part differ in the methods of setting (holding) between them. They can be classified as follows:

adhesive setting (due to mechanical action);
due to metallic bonds:
1. diffusion zone within the boundary of two surfaces;
2. diffusion zone of the entire overburden.

Chrome plating technology involves several stages:

preparatory;
application process;
final.

Preparatory stage. At this stage, those types of work are performed that will allow the chromium layer to be firmly fixed and held on the surface. long time. Before chrome plating of products, they are ground and, if necessary, polished. After the finishing operation, the products are washed, dried and wiped soft material. Those surfaces (holes, internal cavities) that are not subject to metallization are insulated. Parts are installed (hung) on a device that is designed to introduce parts into the processing area. A mandatory degreasing process is carried out. Decaping is performed to increase the adhesion ability.

The process of applying chromium to the surface. The technology of chrome plating of parts, depending on the method of application, occurs in three types:

in a cold state;
in a heated state;
diffusion.

For example, during the electrolytic method, the products are placed in a bath with an electrolyte solution. Working temperature electrolyte depends on its composition. The set temperature must be maintained throughout the entire process, which guarantees a homogeneous structure of the applied layer and a uniform thickness.

Metallized products act as an anode. The duration of the chromium plating process directly depends on the required coating thickness.

After applying chromium products are dried. If drying is carried out in drying cabinet, then its duration will be 5-10 minutes at a temperature of 85°C-100°C. If drying is carried out by blowing compressed air, then its duration will be 0.5-3 minutes at a temperature of 18°C-25°C.

To increase the strength and hardness of the coated layer, it is subjected to heat treatment. The holding time in the oven is several hours at a temperature of about 200°C.
The thickness of the coating applied to steel ranges from 0.003 mm to 0.025 mm. If you use a change in the polarity of the current (reverse), then the thickness of the chrome plating is adjusted to 0.03 mm.

Types of chrome plating

According to the classification, the metallization process occurring due to mechanical adhesion belongs to the first group, and due to atomic mechanical bonds - to the second group. The second group is divided into two subgroups:
2a - border diffusion;
2b - complete diffusion.

Group 1 includes the following chrome plating methods:

electrical coating;
electric arc or flame spraying (pulverization);
chemical application;
vacuum deposition in a cold environment.

Group 2 includes:

plasma spraying;
electrophoresis;
vacuum deposition in a heated environment;
electrotechnical coating with subsequent annealing;
precipitation of pure metal from carbonate compounds in a gaseous medium;

diffusion deposition of elements.

hard chrome plating

Hard chromium plating has found wide application in the manufacture of parts subject to high wear, active corrosion in aggressive environments, in the restoration of metal parts, to increase the service life of tools (cutting, measuring), as well as for decorative finishing of products made of non-metallic materials.

Hard chromium plating is carried out by the following methods:

galvanic (described above);
catalytic, in which chromium is reduced on the surface from ammonia and silver salts;
vacuum, in which the reagent deposited on the treated surface diffusion activity under negative pressure;
thermochemical, which can be compared with the cementation of products.

Thermochemical chromium plating is carried out in a carburetor, consisting of crushed chromium and kaolin in a proportion of 55-45%. To prevent oxidation of chromium during high temperatures hydrogen is blown through the boxes with parts and the carburetor. The duration of chrome plating is three hours. During this time, the layer thickness reaches 0.15 mm at a temperature of 1300°C, and 0.8 mm at a temperature of 1400°C.

Chrome plating by electrolysis

Chrome plating by electrolysis is the easy removal of hydrogen compared to chromium from the electrolyte. The electrolyte is chromic acid. Bathtubs are equipped with lead insoluble anodes.

Sulfate electrolyte based on chromic anhydride with sulfuric acid CrO3:H2SO4 has been widely used.

The concentration of the solution is selected based on the nature of the coating and the complexity of the shape of the part.

At a low metallization temperature (not higher than 35°C), the chrome-plated surface has a gray matte tint. The intensity and density of the current does not affect the process. When the temperature rises to 65°C and the current density rises, the surface becomes shiny. Further increase in temperature and current density (up to 30 A/dm2) chromium has a milky tint.

Also, the quality of the coated surface depends on the electrolyte concentration. The chrome coating obtained using concentrations up to 150 g/l is characterized by high hardness and wear resistance. Highly concentrated electrolytes, up to 450 g/l are used for decorative coatings.

Galvanic chrome plating

Electroplating is the most common modern way chrome plating. It is carried out in two ways: in an electrolyte medium and diffusion. electrolytic method similar to chromium plating by electrolysis, they differ only in the modes of the process.

The diffusion method is the process of surface saturation when certain conditions from applied reagents. Finished parts have: strength and hardness, viscosity and elasticity, wear, heat, corrosion resistance.

Chrome plating equipment

The market offers a variety of chromium coating equipment such as domestic production, and foreign. Private foreign entrepreneurship has inspired developers to create compact units that are easy to place in a garage or a small workshop.

Non-professional equipment only imitates high-quality chrome plating, while the quality is not so good. Work is carried out in the following sequence:

cleaning from the old coating;
grinding;
degreasing;
applying a primer;
spray chromium application;
drying;
varnish protection from damage.

Electrolytic (galvanic) chromium plating is widely used in production. For this, special baths, electrical installations, a ventilation system, washing and dryers. In the hot method of applying chromium, furnaces and vacuum installations are used.

But regardless of the type of equipment used, there are physical and chemical reactions accompanied by the release of decomposition products.

Scope of technology

Decorative chrome plating of parts allows you to increase the visual characteristics of products made of both metals and different kind plastics, glass and other materials. For everyday life, chromium is used for coatings:

furniture fittings;
interiors and design projects;
souvenirs;
plumbing.

Plumbing equipment must be chrome-plated to protect against water oxidation (corrosion), whether it is inexpensive silumin or expensive brass with bronze.
The industry uses chromium plating to improve the durability of parts operating in conditions of high friction:

pistons;
compression rings;
videos;

Chrome plating is also used in the manufacture of tools and equipment:

press dies;
cutting tool;
measuring tool.

Chrome plating technology allows you to extend the life of the elements of the mechanism or give products an attractive look.

The presented training courses are to help beginners who love decorative chrome plating of chemical plating. The purpose of the training courses is to fill the gap of systematized knowledge on the topic of decorative chromium plating by chemical plating and make this technology more accessible to beginners. The submitted texts, photos and videos are personal experience the author, who does not claim to be professional. The author of the training courses is not responsible for possible injuries, burns and poisoning associated with the use of hazardous chemicals such as concentrated acids, alkalis, ammonia. Therefore, do not neglect protective equipment and care when handling reagents.

Decorative chrome plating, chemical plating, all these terms and processes were not known to me not so long ago. Dear friend, since you are on this site, it means that you are also hooked on this topic and you are looking for answers to questions. Questions that haunt you ... How to make any thing with a mirror shine? However, the answers are very close, just sit back and carefully look at the contents of this page. In fact, this is a technology of mirror silvering by spraying. This is also called chemical silver plating. So, there is no talk of real chrome plating, but the name has taken root and is misleading. When I started collecting information on this topic, I was faced with the fact that there is a lot of information on the topic of decorative chrome plating, but to my amazement, nothing specific. All around, yes. Here are a lot of videos where garage craftsmen, as well as pros selling equipment, are happy to demonstrate the process of transforming a nondescript detail into a product sparkling with a mirror. But step by step, all the technology, no one lays out for nothing, inflating a big, big secret out of it ... There are many questions, but the answers are paid ...

After reading a mountain of sites and textbooks, a mess formed in my head, probably, like many others, faced with such a task. So that a clear picture appeared in my head, I decided to immediately practice. It is clear that without chemistry, you will not learn how to chemistry, so I began to search and bypass the offices that sell chemistry. First of all, I asked the price for silver nitrate, since this is the most expensive component. Decide on a supplier. For bought on the list of chemicals, dishes and other necessary utensils. The question arose how to try without equipment. The solution is simple - manual household sprayers. The search and experiments began to create a miracle solution of silvering and application technology. And then one interesting detail about the preparation of chemistry emerged ... All the available information posted on the Internet is a copy of the materials of mainly Soviet textbooks on the topic of chemical metallization ...

Draining a fair amount of silver (respectively, money) to the ground in the process of unsuccessful experiments. Came for a pretty good recipe. In other words, everything is in order. This is the end of the lyrical introduction and the beginning short course how to make a thing mirror. I will not ship the theory, I will leave it for self-study. There is a lot of this goodness on the Internet. Let's get straight to the point. Short, concise, to the point. I will show you on the example of silvering a glass cup.

Technology of chemical metallization with silver, sputtering method

To get the first experience of silver coating on the surface, by spraying, you should learn the technology. And to put it simply - the sequence of actions.

I will list them:
1. preparation of solutions
2. surface preparation
3.surface activation
4. plating

ladies short review listed items. To get the big picture in my head. Let's take a closer look at the lessons of the same name.

Preparation of solutions

To prepare solutions you will need:

stannous chloride
Hydrochloric acid
Nitrate silver
Sodium hydroxide
Ammonia
Glucose
Formalin
Distilled water

We buy chemicals in stores or warehouses of medical equipment.

From the equipment you will need:

Measuring cup for 1 liter
Measuring cup for 200 - 250 ml.
100 ml bottles - 3 pcs.
Disposable syringes for 5, 20 and 50 cubes
Disposable cups 50 ml
Disposable knives and spoons
Electronic balance, measuring up to 200 gr.

We buy equipment in household goods and pharmacies.

You can start preparing solutions with a solution of tin dichloride. Required to activate the surface. For this we take:
1. Stannous chloride
2. Hydrochloric acid
3. Distilled water

The next solution is "silver". We take:
1. Nitrate silver
2. Sodium hydroxide
3. Ammonia
4. Distilled water

Surface preparation

To prepare the surface, it must be degreased. To do this, you can prepare a simple degreasing solution, consisting of:
1. Sodium hydroxide
2. and water temperature 40-60 degrees

The surface should be carefully wiped with a sponge moistened with a degreasing solution. Then wash off the solution with distilled water, wiping, but with another sponge. A sign of good degreasing is the wettability of the surface with water. That is, watering with water, the entire surface should be covered with a water film. If there are dry islands, silver will not stick there.

Surface activation

In order for the metallization reaction to take place precisely on the surface, and not in the sink, it is necessary to activate it, as they say. That is, to help the silver stick to the surface. It is for this that we take a solution of tin dichloride. It's very important point procedure time. Water the part with a solution of stannous chloride for one minute. Then pour with distilled water - three minutes. This is very milestone and non-observance of the surface treatment time leads to marriage, that is, to a waste of time, effort and money. Watering should be as even as possible so that all areas of the surface are equally moistened.

Metallization

This is the most interesting stage of obtaining a mirror film of silver on the surface. Actually for the sake of this, the whole idea. To do this, you need only a silver solution and a reducing agent solution. This will require some skill, which comes with experience. It is necessary to spray so that the solutions mix on the surface and nothing else. And sprayed in equal amounts by volume. Having reached such accuracy, we get an ideal mirror, without defects.

In addition, you should be aware that the mirror film not durable and in order for it to retain its properties, it should be protected with a layer of transparent or tinted varnish. But that's a completely different story.

The process of decorative chrome plating can be repeated even at home in the bathroom without buying expensive equipment with minimal cost. You can learn more about the technology by studying the email course Technology of decorative chrome plating and trying it in practice, it will allow you to decide whether it is worth moving further in this direction.

What does the email course "Technology of decorative chrome plating" consist of?

Chemistry and equipment.
Recipes and preparation of solutions for silvering.
Surface preparation for silver application.
Metallization

This knowledge and skills cost me more than 40 thousand rubles and several months of time. Information is provided to you free of charge, in a concise form and in essence, in the form of 5 short lessons. In order to receive an email course, leave a request by filling out the form located above, under the video. Enter your real name and address Email, then click the "Submit Application" button. After that, you will be taken to a page with instructions to confirm your application. Read it carefully and then go to your mailbox. You should receive an email confirming your application. Click on the confirmation link, and almost immediately you will receive the first letter of the Decorative Chrome Technology course, where you will receive comprehensive information on how to start using the technology.

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

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

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

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

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

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

2 Chrome plating equipment

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

Chrome plating equipment includes:

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

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

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

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

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

3 Electrolyte reagents

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

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

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

The creation of an electrolyte requires the following components:

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

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

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

4 Surface preparation and how chromium plating proceeds

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

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

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

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

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

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

When it enters the groundwater, and then into the wells, chromium oxide causes poisoning and the development of cancer, so it is strongly recommended not to start work without having previously decided on all the intricacies of the process.

Chrome plating is one of the most used and beautiful types of coatings. The deposition of chromium is a physical and chemical action during which a thin layer of chromium metal settles on the plane of the workpiece. It gives the products a wonderful silvery look, and in addition, it protects the iron from rust. You can make high-quality chrome plating at home.

In order to correctly and reliably carry out the process of applying chromium with your own hands, you should take into account all character traits chemical and physiological transformations that take place. Most of chemical elements, involved in chromium plating, is represented by especially dangerous elements, therefore, before proceeding with experiments with chrome plating, it is necessary to carefully study the theoretical side of the process.

Chrome gives the plane a wonderful appearance which gives the product a very elegant appearance. Electroplating opens up great opportunities for improving the decorative, physiological and chemical qualities of materials. Chrome is extremely resistant to aggressive environments, it does not darken when exposed to environment, thanks to this, he found extensive use in the design of car body parts and parts of elements operating in difficult conditions. The thickness of the shiny coating is very small: from 0.075 to 0.25 millimeters.

Unlike nickel, in most cases chromium is not used for metal. For this, a light layer of galvanization is used. This kind of layer consists of copper and requires the use of technological influences, complicating an already difficult process.

Another problem that can stop on the way to the implementation of the task is obtaining reagents. The main component is a chromium compound (CrO3), another name is chromium anhydride. An unpleasant feature of its use is that chromium oxide is the most powerful poison, the lethal dose of which is 6 g. This compound has a small turnover, which is strictly controlled by the state.

Residues arising from the completion of chromium plating must be disposed of in accordance with special procedures and must not enter the sewer or land. The element is a strong carcinogen: if it appears on the skin, there will be very strong irritation, including eczema and dermatitis, a tumor may form.

Reagents for the electrolyte used

It is important to consider all the nuances of the process before you chrome metal at home. The process of chrome plating with your own hands at home is carried out by electrical means. For its implementation, it is necessary to have a cathode, an anode (blank) and an electrolyte in which chemical interactions will be carried out.

A sheet of lead or its compound with tin is used as a cathode. It is most correct that the full-weight record be somewhat larger than the blank. The cathode is connected to the positive electrode. The anode is connected to a material covered with chromium. It must be suspended in the electrolyte medium in such a way that it does not touch the walls, the bottom and does not touch the cathode.

The following elements are needed to form an electrolyte:

chromic anhydride, 250 g/l of electrolyte;
sulfuric acid - 2−2.5 g / l;
the purest, without inclusions, water.

Before making the electrolyte, water is heated to a temperature of 60–80 °C, then dissolved in chromium anhydride. Then you need to slightly cool the solution and add a small amount of sulfuric acid in a thin stream. Acid should not be industrial, but pure. Electrical compensation is very sensitive to the electrolyte formula, so the enterprises have laboratories that continuously monitor the stability of the state of the reagents. If electroplating is carried out at home or chrome plating with my own hands, will have to do without the help of technologists.

Chrome parts equipment

The impact of chromium plating can be not only on metal products, but also on plastics. Chrome plating of plastic at home, for example, headlights, is carried out a little differently. You should be aware that reagents that may be hazardous to health are used to perform the procedure.

For home chrome plating of parts, the following equipment is required:

plastic bath;
a rectifier capable of providing voltage up to 12 volts and up to 50A;
acid-resistant heater for electrolyte heating;
thermometer with a measurement limit of 0-100 degrees.

The parameters and volumes of single types of equipment used for chromium plating are formed depending on the size and quantity of cultivated products. It is necessary to choose the smallest volumes of the bath in which the parts will be immersed. The bathroom can be made from a plastic bucket or other rectangular container. To ensure that the solution does not volatilize during long-term storage, an airtight lid should be guaranteed. Can be used as a rectifier Charger for car battery (suitable for small parts).

Chrome elements will be made in an electrolyte that consists of:

purified water;
chromium trioxide (CrO3) 220–250 g/l;
sulfuric acid (H2SO4) 2.2-2.5 g / l.

In addition to these parts, you will need the following kit: hydrochloric acid (HCl), acetone and sheet metal.

Plane preparation and plating

Independent chrome plating cannot be carried out without proper preparation of the product plane. First, it is necessary to form a copper or nickel-plated substrate, because the element is not in the plane of steel, aluminum or any other alloy.

The copper layer or nickel plating is performed in a galvanic bath. The cathode is metallic copper or nickel, the electrolyte is a solution of sulfuric acid, copper sulfate or nickel. After the end of production, the product is carefully polished, then, in order not to spoil the thin layer of the base, it is necessary to degrease and dry it.

Independent chromium plating must be carried out with stable parameters of all parts. Each deviation can cause damage to the coating. For example, the predominance of the current concentration per unit area leads to the formation of outgrowths and dendrites of metallic chromium in the pointed corners of the products.

Non-observance of the temperature order and fluctuations in the concentration of reagents provoke tarnishing, spotty spraying. After chromium plating of the elements, the shiny plane is covered with the necessary alloy layer, the voltage is turned off, the product is disconnected and placed in a bath with purified water. It is more correct to reproduce the process several times, changing the water.

Stages of chrome plating of elements

Only metals such as copper, brass and nickel can be directly chrome plated. To chrome myself metal parts, you must first apply a copper, brass or nickel layer. This requires the right electrolyte and technology. After drying, the plane is activated in a hydrochloric acid solution (100 g/l).

The processing period depends on the state of the plane (5−20 min). The parts are washed with water and immersed in a chrome bath. To do this, the suspension is made of wire or rod. A "negative" wire is supplied to the suspension. A weighty anode is attached next to the copper rod, to which a “plus” is attached. After 20-40 minutes, the parts are pulled out of the bath and washed in water.

After drying, polishing of the chromium layer is allowed so that the plane is reflective. It is not difficult to prepare an electrolyte: first, chromium anhydride is revealed in water, and then a thin stream of sulfuric acid is added. Before loading parts, you need to hang any plate and turn on the electrolyte for half an hour or an hour.

If a composition with a bright red color turns into a light burgundy shade, then in this case you can include chrome elements. The composition of chromium should be heated to 45 degrees. The current is introduced depending on the surface area of the coated elements. For processing 1 sq. dm requires a current of 15-25 amperes.

The main disadvantages of the coating should not scare beginners. Poor quality layer can be soaked in hydrochloric acid. After that, the parts are washed in water, and the metallization processes are repeated.

Most often there are a number of key disadvantages:

Exfoliation of shiny film. main reason- poor adhesion due to insufficient degreasing. After pulling out the coating, the surface is again cleaned and activated.
Installing chrome in pointed edges. This disadvantage indicates the highest density of the current in the pointed ends. If possible, it is better to round the edges or adjust the screens in problematic areas.
Matte finish. To achieve gloss, increase the temperature of the solution, reduce electricity, or add chromium anhydride.

Before chrome plating with my own hands, n it is necessary to carefully evaluate the future price of the work and conclude that it is necessary. Before shaping a chrome plating fixture, future waste disposal needs to be planned. When it enters the ground, and then into the wells, the chromium compound causes poisoning and the formation of a disease, therefore, it is strongly recommended not to start work without having previously determined all the features of the process. A video tutorial will help you learn the intricacies of chromium coating a metal surface.

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