Metal finishing Q&As since 1989

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Hard coat failure

2002

I have a large alum 36"dia x .750 plate with a 19: ID that has been hard coated anodized. The part is driven by a belt on the OD the ID is rollinr on 6 high carbon steel rollers, with a # 4 finish. The load pressure on each roller is 40 to 50 pounds. The part turns at 2 to 4 rpm rev/min. There is not any lubrication used in service. The base mat. is 6061 t-6 alum. The hardcoat is failing and turning into a dust/powder in only a couple of weeks.

So my Question is what should I do to fix this? Is this the right coating for this application ? Should we use E-nickel instead?

Please advise I'm lost.

Dwayne Conley
- Dayton, Ohio.

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First of two simultaneous responses

Relax, how much worse could electroless nickel be? Electroless Nickel will have the same hardness and much better lubricity and frictional properties.

Todd Osmolski
- Charlotte, North Carolina, USA
2002

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Second of two simultaneous responses

Hardcoat anodize is a very hard but brittle coating. The underlying aluminum provides the support for the oxide. If point or line loading occurs, such as with bearings or rollers, it is possible that the aluminum will deflect in a localized area. This will cause the hardcoat to spall off. Hardcoat works best in sliding load applications where the load is distributed over a larger surface.

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.

Wadsworth, Ohio

2002