Anodizing is an electrochemical process used to create a stable oxide film on a metal surface. As "anodization" itself describes, the metal to form an oxide film must participate in an electrochemical reaction as an anode. The reaction also requires a suitable electrolyte and another cathode material. Since the oxide layer of aluminum alloy is formed by the reaction of the base metal, the oxide layer will not peel or peel off.
Aluminum and aluminum alloys are the metals most commonly used for anodizing. Other metals that can be anodized include: magnesium, zinc, zirconium, titanium, niobium, etc. The anodizing process is not suitable for ferrous metals (such as carbon steel) because the iron oxide (rust, including FeO and Fe2O3) itself is not dense and is very loosely connected to the matrix, and cannot play an overall passivation role.
For pure aluminum and aluminum alloys, the direct effect of anodizing is to increase the thickness of the natural oxide film on the surface. Its main functions are: improving the wear resistance of aluminum alloys; the increase in the thickness of the oxide film is conducive to improve the corrosion resistance of aluminum alloys; the aluminum oxide film itself is transparent and can make the metal appear shiny; anodized parts have good insulation properties.