[Aluminum] Indispensable membrane removal treatment

In the pre-treatment of the anode treatment process, there is a process that is indispensable. We often hear people call this process "neutralization", "ash removal" or "film removal treatment". Here we collectively refer to it as "film removal". Except ".

After degreasing, there is still an invisible oxide layer on the metal surface, or after roughening or polishing, there will be black matter remaining on the surface. We call it "gray matter" because aluminum alloys contain iron, silicon, copper and other metals. substance. Failure to remove the film will affect the anode film formation or cause powdering. Therefore, this process needs to be used to dissolve the oxide film or black film.

Film removal treatment type

At present, the industry still generally uses nitric acid or nitric acid + additives. The main reason is that the nitric acid type will not further corrode the aluminum surface after removing the oxide layer or metal element film, while other types will corrode; but nitric acid will Problems with nitrate nitrogen and ammonia nitrogen will occur, so sulfuric acid system is gradually used for treatment.

The hydrofluoric acid system is used to remove coatings from aluminum castings as mentioned in the table above. Since the surface of the castings contains quite thick silicon elements, it cannot be removed using ordinary nitric acid and sulfuric acid. Therefore, hydrofluoric acid is required to effectively remove it. However, hydrofluoric acid is In addition to the need to declare controlled drugs, you must also be more careful when using them; in recent years, there have been attempts to replace them with hydrogen peroxide-based drugs, but they are still not as effective as hydrofluoric acid.