What is Anodizing?
Anodizing is an electrochemical process that converts the metal surface into a durable, corrosion-resistant, anodic oxide finish. Unlike paint or plating, the anodic oxide structure grows from the underlying aluminum substrate, creating an integral bond that cannot chip or peel [5].
The process involves immersing aluminum parts in an acid electrolyte bath and passing an electrical current through the solution. This creates a porous aluminum oxide layer on the surface, which can then be sealed and optionally dyed to achieve various colors.
Industry Standard Classifications
The aluminum anodizing industry recognizes three main types, each serving different application requirements:
| Type |
Process |
Typical Thickness |
Primary Applications |
| Type I |
Chromic Acid |
0.00002-0.0001 inches (0.5-2.5 µm) |
Aerospace, military applications requiring thin coating |
| Type II |
Sulfuric Acid |
0.0001-0.001 inches (2.5-25 µm) |
Consumer products, architectural, general industrial [5] |
| Type III |
Hard Coat (Sulfuric Acid) |
0.0005-0.003 inches (12-75 µm) |
High-wear applications: automotive, aerospace, hydraulic components [5] |
Type II sulfuric acid anodizing is by far the most common process for B2B manufacturing, offering the best balance of cost, performance, and aesthetic flexibility. Type III hard coat provides superior wear resistance but at significantly higher cost.
Technical Specification: Type II anodizing typically achieves coating thickness of 0.0001-0.001 inches (2.5-25 microns), while Type III hard coat ranges from 0.0005-0.003 inches (12-75 microns) with hardness ratings of 400-600 HV
[5].
