Aluminum and aluminum alloy chemical polishing method

The chemical polishing of aluminum and aluminum alloys is a 70 % ( mass percentage ) phosphoric acid based solution. Commonly used is a mixture of phosphoric acid, nitric acid, and sulfuric acid. When the composition of the alloy changes, the content of sulfuric acid ( mass percentage ) is 9 %. The change is between l5 % and the content of nitric acid ( mass percentage ) varies from 3 % to 9 %. As the operating temperature is around 105°C , a large amount of nitrogen oxides pollutes the environment. Therefore, on the basis of a mixture of phosphoric acid and sulfuric acid, the use of S- type copper brighteners as additives has resulted in a yellow-nosed chemical polishing process. However, such yellow-nosed chemical polishing is only applicable to pure aluminum or aluminum-magnesium alloys, and has a poor effect on other aluminum alloys. Later, there were formulas that only added 2 % nitric acid, and similar additives were used, but the scope of application was not extended. However, since the phosphoric acid, nitric acid, and sulfuric acid mixture is adaptable, it is still the mainstream formulation.

Higher aluminum alloys containing copper and zinc, when chemically polished, add 2 to 5 g /L of chromic anhydride. The manual states that aluminum alloys containing silicon are used. For chemical polishing, a mixture of 60 to 65 mL / L nitric acid, 15 to 20 mL / L hydrofluoric acid, and 1 to 2 mL / L glycerol is used to dilute for 2 seconds at room temperature. However, this method is more like etching.

There is also a formula containing acetic acid, suitable for pure aluminum and 2A 12 (LYl2) :

Acetic acid has a better effect on preventing pitting corrosion.