Anodizing (chromic)

MIL-A-8625/MIL-PRF-8625F Type I, Class 1 is a chromic anodizing process for aluminum and its alloys. Class 1 refers to the thinnest and most basic coating specified under this type, with a minimum thickness of 0.00002 inches.

The purpose of this coating is to provide corrosion resistance and improve the adhesion of subsequent coatings, such as paint or adhesives. It is also used to improve the electrical conductivity of the aluminum substrate.

Type I, Class 1 anodizing involves the immersion of the aluminum part in a chromic acid solution, which forms a thin layer of oxide on the surface of the part. This layer is transparent and can be dyed to achieve different colors. The process is conducted at a low temperature and voltage, typically at or below room temperature and less than 40 volts.

The resulting coating provides excellent corrosion resistance and is often used in aerospace and defense applications where high reliability is required. However, the coating is relatively thin and can be easily scratched or damaged, so it is typically used in conjunction with other coatings for added protection.