Currently, the problems of chromium plating at home are quite acute. The reason for this is the rather high price tag for such services from specialized workshops. The chrome plating of parts and components of mechanisms not only gives them a very effective and attractive appearance, but also improves a number of technical and operational indicators. Thus, a layer of chromium deposited by one method or another prevents corrosion of steel, and therefore, extends the useful life of the product. According to the assurance of metal experts, chromium plating also increases the frictional wear resistance, and even increases the fatigue strength of a metal structure.
General Provisions
The process technology is quite simple, it can be elementarily recreated at home. Chrome plating - applying a surface or diffusion layer to a product made of steel or plastic.
You can apply a layer by several fundamentally different methods:
- galvanic bath;
- galvanic brush;
- flame spraying;
- ion-plasma technologies.
The last two methods are very energy intensive and require expensive equipment. Not suitable for handling parts at home. Chrome plating obtained using flame spraying is much better. But the best result is obtained by ion-plasma treatment in the glow discharge of a vacuum chamber, since in this case the atoms penetrate deep into the product and the layer has very good adhesive properties.
Advantages and disadvantages of a plating brush
The main advantage of the so-called galvanic brush is the absence of restrictions on the overall dimensions of the workpiece. The possibilities of galvanic processing are limited by the size of the bathroom itself. Chromium plating at home of large and weighty products is difficult to put into practice: you will need a large tank, a crane for lifting heavy products, a large volume of mortar, etc.
Not every layman can apply a layer of high quality and evenly, so that the surface is uniform and shiny. Only professionals who are engaged in similar work for a long time and on an ongoing basis can cope with such a task. This is the main disadvantage of this method.
For the chrome plating of parts at home, the simplest galvanic bath is most often equipped.
Safety rules and requirements for galvanic work
It is forbidden to operate the unit in the room in which people live. An ideal place to organize production is a garage or a barn on the street.
In the summer, when the street is warm, you can equip a mini-plating area directly on the street under the roof of the veranda. In city conditions, it is permissible to use the area of the balcony in high-rise buildings for chrome plating at home. In this case, the frame, if any, should be open wide open, and the doors and windows to the apartment should be closed.
Without fail, in order to prevent electric shock and to avoid the harmful effects of chemically active elements, it is necessary to work in industrial rubberized gloves for electricians. To minimize the harmful effects of toxic fumes, wear an industrial gas mask or respirator. To protect against splashes, glasses and an apron made of thick rubberized fabric are used.
Necessary tools and accessories
To implement galvanic chrome plating at home, you will need to buy or find the following elements for the assembly of the installation:
- glass tank (in domestic conditions, an ideal substitute is a regular can for seaming with a volume of three liters);
- a bathtub made of non-metallic material (a plastic basin is well suited for these purposes);
- thermal insulation materials;
- heater (usually a boiler coil is used);
- anode (an alloy of lead with antimony with a mass fraction of the first 93% is ideally suited for the manufacture of this element, the material is rather scarce, therefore, lead of technical purity is most often used for chemical chromium plating at home);
- the cathode is a kind of terminal that closes on the workpiece);
- mercury laboratory thermometer;
- equipment that allows you to hang the item in the bathroom;
- lid for the bathroom (wood and plywood are well suited);
- AC to DC converter with the ability to regulate resistance; to ensure the flow of physico-chemical processes throughout the volume of the banks, the minimum current strength should be 18 amperes.
If desired and with appropriate qualifications, a controlled chromizing process can be implemented at home. The technology provides for galvanic processes at a certain temperature (depending on the surface area of the product, the volume of liquid, etc.) in order to obtain the maximum beneficial effect and quality of the layer.
Above is the simplest installation diagram. The numbers on it mean: 1 - glass container (jar), 2 - anode (or anodes), 3 - chrome-plated part (cathode), 4 - electrolyte solution.
To control the temperature, you need a simple thermocouple and a potentiometer. Such equipment can be easily found in flea markets.
Do I need to clean the surface of the product?
The result of the process depends on many factors. But the greatest influence is, of course, the quality and cleanliness of the surface on which the chromium layer will be applied. To rationally use the time, all work on the preparation of parts is recommended to be carried out during the preparation and heating of the electrolyte. Heating the electrolyte to operating temperature takes no more than three hours.
Therefore, we can say that cleaning the surface of products is a very important stage of the technological process. And if you neglect it, then the quality of the chrome layer will be very poor, and soon such a coating will begin to swell and peel off.
How to clean the surface
The best way to clean the surface of grease stains and dirt is to immerse them in an ultrasonic bath. In production conditions, they do so. This is a very effective method. Currently, it is relatively inexpensive to purchase a small bathtub. But such costs will pay off only if it is planned to regularly and often set the chrome modes.
Usually, people clean parts manually. Yes, this method is less productive, and the quality of cleaning is sometimes not so good, but still it is a good alternative to acquiring an ultrasonic cleaning bath.
It is believed that it is best to chrome surfaces with a slight roughness. This ensures a good and reliable adhesive interaction of materials. Therefore, it is recommended to go over the part with fine sandpaper.
Washing operation
When washing the product, the first thing to do is to rinse it in water (preferably flowing). This will eliminate coarse foreign particles. The next step is to degrease the part. Alcohol and acetone leave insignificant streaks when dried. Therefore, it is recommended to prepare a special solution: add 150 grams of caustic soda, 50 grams of soda (calcined) and 5 grams of silicate glue to one liter of water.
The prepared solution is heated to a temperature of at least 90 degrees Celsius, and the parts are placed in it for 20 minutes. After removal from the container with the cleaning solution, the products are removed and dried, then further technological operations can be carried out.
Electrolyte Preparation
It is possible to prepare an electrolyte solution without problems at home. Chrome plating occurs in a solution of sulfuric acid and chromic anhydrite in water. Such a solution is called an electrolyte. The concentration of sulfuric acid is approximately 3 grams per liter of water, chromic anhydride is about 300 grams.
Water purity also has special requirements. Ordinary tap water is unsuitable here: due to the high concentration of impurities, the process will proceed unpredictably, and the result will be of very poor quality. Thus, to prepare the solution, you need to buy distilled water in sufficient quantities.
Before the component is added to the solution, the water must be heated to 60 degrees Celsius. This guarantees a complete dissolution of all components and a high-quality electrolyte for chromium plating at home. Electroplating is a branch of science and technology that requires the utmost attention and accuracy from the contractor and supervisor. Chromic anhydride is a very toxic and dangerous compound. Therefore, you can work with it only in well-ventilated places. It is best to use a chemical hood with a powerful hood. If you seriously approach the matter, then such a cabinet can and should be made with your own hands. Chrome plating at home should be carried out in strict accordance with all requirements and safety rules.
Preparation of electrolyte for work
Before immersion in the electrolyte of the product, it is necessary to pass the current through the solution “idle”. In the event that all the parameters of the system were calculated correctly and the current was selected to the desired value, the solution should acquire a dark brown hue. The general recommendation is that in order to ensure that the process runs along the entire volume of the electrolyte, a current of six and a half amperes per liter of liquid is required. Current is passed for 4 hours.
After the liquid has darkened, it needs to settle. Therefore, you must not touch the bath for at least one day.
Galvanizing
First you need to inform the temperature of the working medium (electrolyte) 53 degrees Celsius. This will provide the most favorable conditions for the course of all processes.
Then it is necessary to suspend the products on the support so that it is completely dipped into the electrolyte. It is necessary to wait for some time (5-10 minutes) so that the temperature between the electrolyte and the product becomes equal.
It is not recommended to immediately conduct the mode on a real part. First you need to test the technology on some prototype. Even if it is spoiled, it’s not a pity.
Once the regularities of the formation of the layer and its dependence on the supply time of the voltage, the composition of the electrolyte, etc., are revealed, we can begin mass production of products.
Features of chrome plastic do-it-yourself at home
It is not possible to use a galvanic bathtub when coating plastic products because plastic is an insulator (with the exception of special materials designed for specific tasks) and does not conduct current, which means it cannot act as a cathode in an electrical circuit.
Therefore, plastic products are coated with a decorative layer of chromium using a completely different technology: initially two or three layers of a protective auxiliary coating are applied to the product, and then a layer of chromium. And despite the small thickness of such a layer, it serves well and is quite able to cope with the tasks that were assigned to it.
Preparation of plastic products for chrome plating
Like steel and metal alloy products, plastic structural elements must also be well washed and degreased before chrome plating. It will not be superfluous to process all surfaces with fine-grained emery paper. This set of operations will provide reliable contact between the plastic and the applied metal layers.
Sulfuric Acid Treatment
An obligatory step in preparing for metallization of plastic products is the etching operation. The essence of this operation is as follows. A special solution is prepared (60 grams of chromic anhydride, 150 grams of phosphoric acid (rust converter), 560 grams of sulfuric acid per liter of distilled water). Products are immersed in the solution for a certain time. It is hard to say what time it will take specifically. It is determined empirically and depends on many factors. Thus, the chrome plating of plastic at home does not differ in repeatability and constancy, and each new mode can take place with its own characteristics. An important point: before immersing plastic products in the bath, the temperature of the medium must reach at least 50 degrees Celsius.
Only after carrying out all these operations can you start applying a metal coating.