Chrome plating treatment can be used both for decorative purposes and to improve the technical and operational properties of the workpiece. For metal products, this coating method is especially relevant, as it reduces the risk of corrosion damage. The technology is used not only in industry, but also in the private sector - for example, to decorate and protect the exterior parts of a car. How to chrome metal at home? There are several relatively accessible methods, each of which provides for its own implementation nuances, but there are also general rules for organizing this process.
Preparing the part for chrome plating
The quality of the applied coating directly depends on the condition of the working surface. It must not only be cleansedfrom dirt and dust, and subjected to mechanical cleaning with abrasives. Grinding machines should eliminate the flaws characteristic of problematic parts in the form of minor damage, scale, rust and traces of old paint. The structure of the base of the product should remain directly on the surface. This is a basic preparation condition under which you can chrome metal at home, expecting a positive result. Moreover, special attention is paid to persistent grease stains, which also interfere with the processes of applying chromium. At a minimum, aggressive chemical solvents, mineral spirits or gasoline should be used for this treatment. For a more reliable effect of cleaning from fat and oil films, experts also recommend using compositions based on caustic soda, silicate glue and soda ash, preheating them with a temperature regime of up to 85-90 ºС
Processing conditions
In the process of chrome plating, regardless of the processing method used, the release of harmful fumes is inevitable, so living quarters should be immediately abandoned. The best place is a garage, utility room or other technical room. But that's not all. It is necessary to think about stable ventilation with efficient exhaust. It is impossible to rely on natural weathering, since harmful substances can have an impact already during the work. How to chrome metal at home without causing harm to he alth? Even if ventilation is available, personal protective equipment should be prepared. Required kit includes constructiongoggles, respirator, apron and rubber coated gloves.
Preparing the container for chrome plating
In any case, to perform the procedure, you will need a conditional bath to keep the part in the working solution. Depending on the size of the part, a 3-liter jar, a basin, a tank or a classic bath can be used. The only limiting parameter of choice is the material of manufacture - glass or metal that does not enter into chemical reactions with the electrolyte. Next, you should deal with the arrangement of the selected container. First, it must be placed on a level surface and fixed in a stable position so that the chromed metal is evenly coated. Secondly, in cold weather, thermal insulation of the container will be required, which can be used as fiberglass, mineral wool or bulk material (sand, expanded clay). At the same stage, fixtures or structures are thought out for convenient holding of the workpiece and functional devices that will be used at different stages of the operation.
Sources of electric current
When performing metallization at home, electrodes are needed that will be connected to the workpiece to provide an electrochemical reaction. A negative cathode must be connected to the product, and a positive anode must be connected to the solution. The shape of the electrodes is selected according to convenience; both rod and plate elements can be used. But how to chrome metal so that throughoutoperation did not open the contact? For a circuit with current supply to the part, an alligator clip should be provided. It securely grips the workpiece in the desired position. If you plan to process a compact, lightweight part, this gripper will also replace the tool holding in the solution. An ordinary rheostat can act directly as a current source with sufficient voltage. For small workpieces, wires up to 2.5 mm2 will suffice.
Electrolyte Solutions
Ordinary motorists for this procedure use a simplified composition based on chromic anhydride (250 g/l) and sulfuric acid (up to 3 g/l). It is important to keep in mind that the main ingredient of hexavalent chromium is the above anhydride, and trivalent - chromium chloride or sulfate. The second scheme is used less often, since such a composition has a significant impact on the textural and textural properties of the part. As for the temperature regime, high-quality chrome-plated metal can be obtained at 45-60 ° C, but this range can be expanded depending on the chosen technology. Now we can take a closer look at the methods for implementing the task.
Electrochemical technology
The most common method that is widely used in the household. Instructions for its use look like this:
- The prepared container is filled with water by about 60-70%. Importantnote that the liquid must be pre-filtered - it is best to use settled distilled water.
- The container warms up until the temperature of the contents reaches approximately 60 °C.
- The calculated volume of chromic anhydride is poured. It should be thoroughly mixed with water.
- At this stage, you may encounter the problem of lack of the required amount of water. How to chrome metal at home, if it becomes necessary to correct the proportions of the solution? It is advisable to avoid this, but in any case, it is recommended to make adjustments in the direction of increasing the volume of water to fill the desired tank level.
- Sulfuric acid is added in the right amount.
- After stirring the solution again, it should be allowed to settle for 3-4 hours when the current is applied at the rate of 6.5 A per 1 liter. As the reaction proceeds, the electrolyte will gradually acquire a dark brown hue.
- The power source is turned off, after which the capacity is infused for another day.
Possible marriage when performing chrome plating
If the operation is performed for the first time, then there are big risks of getting various kinds of defects. How to chrome metal at home to eliminate such a possibility? To do this, you need to know the specific reasons for the appearance of marriage:
- There are small pits on the surface - insufficient abrasive treatment was carried out on the part.
- Covering peeling - current source was supplied with voltage drops.
- The chrome layer is softened - toohigh temperature and low current.
- There is no characteristic shine on the surface - evidence of an overestimated current strength or an excess of the chromium component in the solution.
- Shine is uneven on surfaces - lack of temperature or a sign that the solution was poorly mixed.
- Brown spots - a small amount of acid against the background of an excess of chromium.
Alternative chrome technologies
Another way to apply chromium is diffuse. But it is used purposefully for surface modification due to the combined effect of silicon, carbon, aluminum and nitrogen at high temperature. How to chrome metal at home using the diffusion method? The technology provides for wetting in hydrochloric acid, after which laying is carried out with powder mixtures, followed by exposure to gases. A subtype of this method is condensation treatment with chromium chloride vapor, but it is usually performed on technologically sophisticated equipment. Also worth noting is a method called "silver mirror". Its essence lies in the deposition of silver s alts in an alkaline solution. Further, it is necessary to use auxiliary solutions containing hydrazine and invert sugar. To give the coating a certain color at the final stage of processing, special paints and varnishes can be used.
How to restore chrome on metal?
Technically, the structure of this coating can be restored only by decapitation. It consists in re-immersing the part insolution with sulfuric and hydrochloric acids in the required concentration, which depends on the size of the part and the current state of the chromium layer. After this procedure, the workpiece is washed with warm water and infused for several hours in a dry place. More affordable ways to restore a chrome coating on metal involve the use of special pastes produced by auto chemical manufacturers. Such products are literally rubbed into the microfiber coating structure, forming a protective film and filling small damage pores. Grinding procedures also help to correct the imperfections of the chrome surface, but their effect erases the coating over time. For this reason, it is recommended to use additional protective equipment as a preventive measure. Among them are the simplest folk recipes based on crushed chalk and ammonia. However, these materials should be rubbed only with soft sponges and napkins.
Can other materials be chrome plated?
Theoretically, any material with a porous structure on the surface can be subjected to electrochemical metallization, which will ensure sufficient adhesion. Unlike metals, plastic and ceramics are chromium-plated in less aggressive temperature conditions. This nuance applies to all products that are sensitive to temperature effects. Otherwise, the conditions remain the same - both in terms of technical preparation and in terms of preparing an electrolytic solution.
Conclusion
The result of chrome plating is equally valuable andaesthetic effect, and the creation of a protective coating. In the first case, you can count on getting the attention-grabbing shine, which was mentioned above, and in the second, on extending the working life of the part. Even metals chrome-plated at home add wear resistance, strength and hardness properties. For additional hardening of critical parts, special heat treatment of the coating is sometimes used with exposure at temperatures up to 200 ° C. On the other hand, chromium plating also has weak points. Over time, the coating wears out even under conditions of minor mechanical stress, which is why experts strongly recommend taking care of its protection from the very beginning of the operation of the updated surface. As for the processing method itself, with all its availability for home use, it also has a big minus. It is expressed in the toxicity of the electrolytes used, which necessitates compliance with appropriate safety measures.
