Aluminum is a fairly soft metal. Any product from it loses its original form over time, scuffs, oxides appear on the surface, the product dims. If you want to give the old thing a new look, you should polish aluminum. To do this, you can use one of the following methods:
- electropolishing;
- chemical polishing;
- decorative etching.
Methods of polishing aluminum: chemical method
This technology is environmentally friendly, simple and fairly fast. It can be implemented with acid-resistant steel, which will form the basis of the polishing bath. If the scope of work is relatively small, you can use porcelain crucibles. Acid solution is poured into the container:
- sulfuric;
- nitric;
- phosphoric.
Products are immersed in a hot solution, the temperature of which should vary from 90 to 120 ° C, the final value will depend on the type of aluminum. Exposure to the composition of aluminum is necessary for 30 seconds or minutes, repeat the action should be about 6 times. At intervals, the parts are washed, and they must be shaken constantly.
Chemical polishing of aluminum will be better if you use a drum rotating at a certain speed. After completion of such manipulations, a film of contact copper will remain on the surface. It should be removed by washing the product under running water with a low temperature. This must be done in a catcher. In the next step, the products are treated with 30% nitric acid.
Additional work recommendations
Aluminum polishing can be carried out using alkali solutions:
- trisodium phosphate;
- sodium nitrate;
- caustic soda;
- sodium nitrate.
Their temperature should be higher compared to the acid method, the limit is 120-140 ° C. It is necessary to sustain products about 5-20 seconds. When such a technique is used, aluminum loss will be approximately 8 μm of the total layer thickness.
Using Electropolishing
Polishing of aluminum can be carried out in another way. At the same time, it is possible to obtain a sparkling and smooth surface, and the cleaning is characterized by high quality. Electrolytes for such work in most cases have sulfuric and phosphoric acid, the remaining components will depend on the material.
Electrolytes can achieve shine after completion of work. For the process, the temperature should be lower than in the above case, the temperature limit will be from 60 to 90 ° C.
Polishing must be done within 5 minutes, while the current density can be 10-50 A / dm². The polishing process involves the use of lead cathodes, however, there are other alloys that involve the use of stainless steel. Polishing requires the use of duralumin suspensions, as well as electrolyte baths with polyethylene, lead or fluoroplastic treatment. It is necessary to prepare alkaline electrolytes, they will be cheaper.
The parameters of the process will be affected by the composition of the electrolyte, the temperature limit can vary from 40 to 95 ° C, as for exposure, it lasts from 3 to 6 minutes, while the current density at the anode is from 3-20 A / dm². When choosing cathodes, nickel-plated should be preferred.
Features of decorative etching
Polishing of aluminum can be carried out in a decorative way. This technique acts as a subspecies of electro polishing. Aluminum alloys are etched by anodes according to the regime in a phosphorus-chromium electrolyte. A crystalline pattern forms on the surface of the products, which looks like rosettes or frost. All parts are hung on the anode rod, and then you can start processing. Manipulations should be carried out at a voltage of 25-30 V. By the end, the voltage rises to 35-40 V, the anode current density will be equal to the limit of 8-12 A / dm², while the temperature will vary from 50 to 80 ° C.
After about 20 minutes, a pattern appears. If the voltage starts to rise arbitrarily, then we can consider the process complete. After the end of the manipulations, the products are washed, dried well, anodic oxidation is carried out above them. Aluminum is then stained with organic paint.
Mirror shine of aluminum can be obtained by another method of anode etching, which is called sparkling. For this product, before and after the process are subjected to heat treatment according to a special scheme. You can use anode etching "snowball", which allows you to create a matte-sparkling surface.
What is the best way to use at home
Polishing paste is one of the most commonly used home polishing agents for aluminum polishing. This is due to the fact that the chemical compounds are toxic, they are dangerous to human health. For polishing, you can apply:
- sand paper;
- hard brushes;
- varnish;
- rags;
- alcohol type cleaning products.
When choosing sandpaper, it is important not to overdo it with grit, because otherwise you will have to remove scratches. To increase wear resistance and give shine, it is better to use varnish.
Features of electrochemical polishing
Electrochemical polishing of aluminum involves the implementation of work by the method of parallel chemical and electrical effects. According to the technology of this method, the part acts as an anode electrode, and a positive current supply source is connected to it. The workpiece with the current supplied to it must be immersed in a tank that is filled with electrolyte. The role of the second electrode are copper cathodes.
Using a polisher
The polishing machine is a very convenient way to give the aluminum an initial shine. To do this, you can use a polishing wheel for 1000, which is wetted with water. Use a sponge or cloth to apply water to the area to be treated. Next, a polishing machine for 1400 revolutions per minute is turned on. At a similar speed, the spray will fly about 1 meter around.
The surface of the aluminum will warm up, the liquid will evaporate. You should be prepared for the fact that the circle will become clogged with aluminum "porridge". Therefore, every minute the machine should be stopped to wash the abrasive wheel with a wet sponge under running water. To do this, some craftsmen use a regular spray bottle.
The "porridge" should also be removed from the part. Mirror shine will turn out if you additionally use also felt. This stage is one of the most important. It will depend on him 80% of the final result. Felt should protrude 10 mm behind the base, the circle should be moistened by spraying it with a spray. The part is wetted with a damp sponge. The polishing paste is used coarse, its application should be carried out on the part, and not on the circle.
Conclusion
Do-it-yourself polishing of aluminum can be done by different means, but one of the most effective is paste. It does not contain ammonia additives and is able to gently clean the part from roughness and scratches. With this composition, you can achieve the initial shine. The protective layer will eliminate the occurrence of oxidation over a long period.