HARD ANODISING OF ALUMINIUM ALLOYS

Hard anodising is an electro-chemical process which builds an aluminium oxide Al₂O₃ surface onto aluminium alloys. The coating thickness and density is higher than those found in normal sulphuric acid anodising.

The hardness of a normal hard anodised surface is 60-70 HRC or 8-8.5 in MOHR scale.

Typical qualities of hard anodising:

• Excellent abrasion resistance
• Excellent corrosion resistance
• Excellent insulation properties (2000 VDC)
• Creates an evenly anodised surface including inside holes and on threads
• Corrosion resistance can be additionally improved by using various sealing processes. However there is some sacrifice of the materials abrasion resistance
• Coatings to a certain extent can be dyed
• Coatings can be sealed with a Teflon® solution which dramatically decreases friction. At the same time corrosion resistance is also improved dramatically. Teflon® sealed surfaces are able to tolerate continuous 5 % salt spray solution (+35ºC) (ASTM B-117 and DIN 50021 standards) for more than 2000 hours without corrosion.