Aluminum chemical polishing technology

1. Mechanical polishing on the surface of aluminum products:
1. The mechanical polishing process is: rough grinding, fine grinding, polishing, polishing, sandblasting, brushing or rolling, etc. Different processes are appropriately adopted according to the roughness of the surface.

2. Chemical degreasing:

The chemical degreasing process uses chemical reactions and physical and chemical effects to remove oil stains on the surface of the parts. Chemical degreasing is carried out in a weak alkaline solution.

Formula and process conditions of chemical degreasing liquid:

1. Formula: Sodium hydroxide 30-50G/L, industrial detergent 0.5-1ML/L, water 70-125G.

2. Process conditions: Temperature: 50-60℃ Time: 1-2min

3. Rinse with water after degreasing.

4. Chemical removal of oxide film: pickling treatment to neutralize the residual lye on the surface of the part and remove its natural oxide film to expose the aluminum and aluminum alloy matrix of the part. For the production of silicon-containing aluminum alloy, it must be used The mixed solution is pickled to remove the dark silicon floating dust on the surface.

The formula of the pickling liquid:

Concentrated nitrate liquid 200″270ML/L

Temperature: Room temperature time: 1-3min

The formula of pickling solution for removing oxide film and silicon floating ash on the surface of silicon-containing aluminum alloy parts:

3 volumes of concentrated nitric acid; 1 volume of concentrated hydrofluoric acid.

Temperature: Room temperature Time: 5-15min

After the aluminum and aluminum alloy parts are chemically pickled, they must be cleaned immediately with running warm and cold water to remove residual acid, and then immersed in water for chemical polishing.

5. Chemical polishing:

Chemical polishing is a chemical processing method that uses the selective self-dissolution of aluminum and aluminum alloys in acid or alkaline electrolyte solutions to level and polish the surface of the year to reduce its surface roughness and PH. This polishing method has the advantages of simple equipment, no power supply, no limitation on the size of the part, high polishing speed and low processing cost.

The purity of aluminum and aluminum alloy has a great influence on the quality of chemical polishing. The higher its purity, the better the polishing quality, and vice versa.

Chemical polishing is carried out using a brief theory of viscous liquid film.

Polishing liquid formula and process conditions:

Formula 1: (parts by weight)

Concentrated phosphoric acid 75%; concentrated sulfuric acid 8.8%; concentrated nitric acid 8.8%; urea 3.1%; ammonium sulfate 4.4%; copper sulfate 0.02%.

Temperature: 100-200℃ Time: 2-3min

Formulation 2: (parts by weight)

Concentrated phosphoric acid 85%; concentrated nitric acid 5%; glacial acetic acid 10%.

Temperature: 90-105℃ Time: 2-5min

Preparation method of polishing liquid:

1. Pour phosphoric acid, sulfuric acid, and nitric acid into the polishing tank gradually according to a certain weight (%), and carefully block them.

2. According to the ingredients of the formula, dissolve a certain (%) weight of glacial acetic acid, urea, amine sulfate, and copper sulfate in the tank and mix well.

3. Then, under agitation, gradually adjust the polishing liquid to the temperature range required by each formula, and then chemical polishing can be carried out.

3. The influence of chemical polishing process conditions:

1. Temperature influence: The temperature should be controlled between 90-115℃, and the best temperature is 105℃.

2. The effect of polishing time: polishing time is inversely proportional to polishing temperature, low temperature prolongs polishing time, high temperature shrinks polishing time.