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Compatibility of hard anodized 6061-T6 aluminum billet machined part with EN plated 7075 aluminum blllet machined part

Specifically an automotive brake caliper machined from billet aluminum and EN plated using pistons machined from 6061 and hard anodized. After a very short time of use the pistons look corroded as though exposed to salt water.

Are these two processes compatible within the same assembly when exposed to heat @ 300*F and synthetic automotive Dot 4 brake fluid [on eBay or Amazon] ?

39889

Ashley Page
- Mooresville, North Carolina, USA
2006

There is "hard coat" and there is "hard coat" and it all varies from one job shop to another as definition standards have not yet been written.

But the scientific work has been done on thermal expansion. The aluminum oxide in hard coat has 0.2 times the coefficient of expansion as the underlying aluminum. At your temperatures there will be some cracking.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2006

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