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-----Testing Hardcoat with Conductivity Tester
Quickstart:
In the anodizing of aluminum the components are immersed into a tank of acidic solution and connected to the anodic (+) positive pole of a power supply. The current separates some of the water in the solution into positively charged hydrogen and negatively charged oxygen. The oxygen is attracted to the positively charged components and converts the skin of the aluminum to aluminum oxides.
Readers new to anodizing of aluminum may wish to view our "Intro to Aluminum Anodizing".
Hard anodizing, hardcoated aluminum, will have low conductivity due to a thickness of non-conductive anodized film on it.
Q. I have a tool (6061 Al) that was welded (2139, machined, and then anodized (hard coat). The appearance looks like an alligator skin with a montage of green and silver marks. Can you test with a conductivity tester to see if the hardcoat is present?
Mike RuleEngineer - St Louis, Missouri, USA
2007
A. Hardcoat conductivity can be tested by ohmmeter with two metal contacts. Set the scale limit to 1 k-ohm, slightly touch the surface with two contacts in the distance 1-2 sm from each other. If ohmmeter reading shows more than 1 k-ohm, that it is good anodizing. However thickness of the coating can be tested only in metallographic laboratory with special equipment.
Anna Berkovich
(ed. update July, 2025: sorry, Anna has retired)
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