The role of anodic oxidation treatment for aluminium and aluminium alloys

Let's talk about the role of anodic oxidation treatment for aluminium and aluminium alloys. Aluminium and its alloys are oxidised in the air. The oxide film formed naturally on the surface of aluminium is amorphous, which causes the surface of aluminium metal to lose its original lustre, and although this natural oxide film makes the surface of aluminium metal slightly passivated, it is very thin, about 4-5nm, and has a large porosity and poor mechanical properties. After anodising, the surface of aluminium and its alloys can be given a dense film layer (from tens to even hundreds of microns) that is much thicker than the natural oxide film. This artificial oxide film is then closed and the crystalline oxide film is transformed into a crystalline oxide film and the pores are closed, thus making the surface of the metal lustrous for a long time, corrosion resistance and mechanical strength are improved, and a decorative appearance can be obtained by dyeing. As aluminium and its alloy products have many characteristics after anodising, the aluminium anodising process is widely used in the surface treatment of aluminium products. The applications in industry can be broadly classified as follows.

(1) Prevention of corrosion of products

As the film layer obtained by anodising is properly closed, it has good stability in the atmosphere. Whether the oxide film is obtained from sulphuric acid solution, oxalic acid solution or chromic acid solution in the normal process, its corrosion resistance is excellent, e.g. aluminium pots and pans for daily use, washing machine liners, etc. The chromic acid oxidation method is particularly suitable for aluminium welded and riveted parts.

(2) Protection - decoration

In the acquisition of high transparency of the oxide film, oxide film has the characteristics of a variety of organic dyes or inorganic pigments can be adsorbed, oxide film can be obtained on a variety of bright and vivid colours and patterns, coupled with the emergence of many new processes in recent years such as an oxidation of multiple coloring, gift patterns, wood grain patterns, oxidation offset transfer printing, porcelain oxidation, etc., so that the appearance of aluminium more beautiful and pleasing, this layer of colour film is both a decorative layer, but also corrosion protection layer, such as lighters, gold pens and crafts.