Type I,
Chromic Acid Anodizing (CAA)

First commercial type of anodizing
Compatible with many aluminium alloys
Widely used in aerospace and defense
Minimise metal fatigue
Resist corrosion: 336 hours of 5% salt spray resistance as per ASTM B117

Chromic Acid Anodizing

Thin anodic coating: .00002”-.0001” (20 to 100 micro inches).
Surface finish will be gray and since it is thin, it will not be possible to add color.


Good for tight tolerance parts because it will not change dimensions. This type of anodizing is also great for bonding, welded parts and assemblies. Finally, the Chromic Acid Anodizing is non-conductive.


This type of anodizing is good for aerospace components as either a final finish, a base for paint or as a companion finish to hard anodizing (multi-processes).

Sulfuric Acid

Type II, Sulfuric Acid Anodizing (SAA)

Most frequently used type of anodizing, this process will generate a decorative or protective surfaces with a greater durability than surfaces treated with type I. Sulfuric anodize provides a minimum 336 hours of 5% salt spray resistance per ASTM B117.


Type III, Hardcoat Anodizing (HCA)

The primary objective of this process is to obtain a hard coating, resistant to abrasion. It is obtained using an electrolyte of sulfuric acid at low temperature with high voltage and current density.

Boric Sulfuric

BAC 5632 / MIL-A-8625 Boric Sulfuric Anodizing

Developed by Boeing Aerospace as a chrome free alternative to type I, for non-critical fatigue part. The adhesion to paint is equal or superior to Type I and this type of anodizing provides corrosion protection.