Sulfuric acid is the most
commonly used anodized coating. Coatings of
moderate thickness 1.8 um to 25 um (0.00007” to
0.001”) are known as Type II, as name by
MIL-A-8625. Coatings thicker than 25 um (0.001”)
are known as Type III, hardcoat. Type III is
produced in a refrigerated tank near the
freezing point of water with higher voltages.
Hard Anodizing can be made between 25 and 150 um
(0.001” to 0.006”) thick.
Anodizing thickness increases wear resistance,
corrosion resistance, ability to retain
lubricants, and provides better adhesion for
paint primers and glues than bare metal.
Standards for sulfuric anodizing are MIL-A-8625
Types II and IIB, AMS 2471 (undyed), and AMS
2472 (dyed). Standards for MIL-A-8625 Type III
are AMS 2469, BS 5599, BS EN 2536 and the
obsolete AMS 2468 and DEF STAN 03-26/1.
- Allows coloring
- Ease of maintenance
- Corrosion resistance
- Increases surface hardness