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Ted Mooney, P.E. RET
Pine Beach, NJ

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Aluminum pulley locks itself onto stainless shaft

I have a stainless steel shaft from gear box running into an aluminum pulley (with belt drive). Over a period of very high speed runs, the fit on the shaft and pulley became a press fit from a clearance fit. There was some kind of reaction happening with Al and SS material as the steel shaft was eaten up on the surface. Could any one explain me why this is happening?

Thanks,

Aaron Presley
Packaging Industry - Chicago, Illinois, USA
2003

2003

Aluminum is an active metal that 'anodizes' itself; that is, some of the aluminum turns to aluminum oxide. The anodized coating is about twice as voluminous as the aluminum consumed, such that the I.D. gets smaller. Stainless steel is a passive metal, so there is a galvanic current accelerating this process.

One solution would be to have the pulley anodized so its growth has stopped before you mount it on the shaft.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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