Structural characteristics of anodized film on industrial aluminum profiles

Anodizing of industrial aluminum profiles is the most common surface treatment method. Natural color oxidation can maintain the original metallic color of industrial aluminum profiles, and the color is more uniform and bright. The anodized aluminum profile improves its wear resistance and corrosion resistance. Today, let's take a look at what kind of structure makes the oxide film so powerful?

The chemical composition of the anodized film on industrial aluminum profiles is actually aluminum oxide (Al2O3), which is hard, transparent, and has a unique structure. Compared to the oxide film of other metals, it is dense and porous. The regular micropores are perpendicular to the surface, and the structural unit size, pore size, 40 · Jan. 1999 Electroplating&Finishing Vol. 18 No.1 wall thickness, and barrier layer thickness can all be controlled by the composition of the tank liquid and process parameters. The thickness of the oxide film is directly proportional to the electrification time within its limit thickness range, which means that the longer the electrification time, the thicker the film.

Generally speaking, the length (film thickness) of a hole is more than 1000 times the pore size. The porosity is usually around 10%, and the porosity of hard films can be reduced to 2-4%; The ordinary oxide film is about 11%. So after anodizing, it is necessary to perform sealing treatment to protect the substrate of the aluminum profile. Aluminum profiles that require oxidation coloring also need to add some metal salts to the tank solution before sealing, so that these metal salts deposit in the gaps of the oxide film, forming different colors. For example, iron salts can form deep red and black; Copper salts can form blue and green.