MIL-A-8625, AMS 2469, AMS 2482
Hard anodising is a sulfuric acid based electrolyte, is much thicker and denser than the more conventional sulfuric acid anodizing. Hard anodizing is specified for aluminum components subject to extreme wear applications where superior abrasion resistance is needed, or corrosive environments where a thicker, harder, more durable coating is necessary. It can also be valuable where enhanced electrical insulation is required.
Hard anodizing with PTFE impregnated aluminium oxide been used typically to increase surface hardness and resistance to abrasion and corrosion of aluminum alloys
TYPES
Type III – Hard anodizing
CLASSES
Class 1 – Undyed (Sealing – Deionised Water, Dichromate, Nickel Acetate)
Class 2 – Dyed (Red, Black, Customized)
HARD ANODIZING -PROCESS CONTROL & TEST METHOD
VISUAL INSPECTION – MIL-A-8625 & CUSTOMER SPECIFICATION
THICKNESS TEST – ASTM B 244
COATING WEIGHT TEST – ASTM B 137
CORROSION RESISTANCE TEST – ASTM B 117
ABRASION RESISTANCE TEST – ASTM D 4060
CO-EFFIECIENT OF FRICTION TEST – ASTM D 1894