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DI Water Protection for Aluminum

Anyone have a recommendation regarding the best plating on AL for use in a DI Water environment? Is el-ni better or worse than hard coat anodize? Any links going into depth on this topic?

Thanks in advance.

Charlie Smart
- Stamford, Connecticut, USA
2003

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If it were my aluminum part, I'd sooner go with hard anodize AND A CORROSION EXTENDING SEAL than with electroless nickel. A single pin hole in EN over aluminum will result in more severe corrosion of the aluminum than if the entire aluminum part was left uncoated. The worst corrosion cells are where there is a small anodic area (the aluminum)with a large adjacent cathodic area (nickel).

The caution on SEALING the hardcoat is stated since most hardcoat on aluminum is provided unsealed for maximum abrasion resistance. Unsealed hardcoat is NOT ADVISED for applications where corrosion may occur. Sealing with nickel acetate, hot DI water, or PTFE must accompany the hardcoat anodize.

I'd guess that the sealed hardcoat alternative is also cheaper than the EN alternative.

Milt Stevenson, Jr.
Plating shop technical manager - Syracuse, New York
2003

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