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topic 4541

Black EN


Since a few month we are plating small steel parts with 12 µm EN. Since two weeks we have problems: After less than 0,3 MTO the EN layer becomes blackish ore anthracite. We didn't change anything. We repeated that "game" for four times, but it's always the same - it begins with very bright EN and after a few charges it turns to anthracite coulored layers. Can anybody give me a hint?

Klaus-Martin Hentrich
- Velbert, Germany


You are probably contaminating your tank with copper or cadmium or aluminum or gross amounts of iron.

Drag in is my first guess. This is probably a shared line

The EN tank might be close to a chrome tank where the hood is shut off when not in operation or is inadequate.

At the price of nickel these days, it deserves its own preprocess line.

James Watts
- Navarre, Florida


It sounds as if you are shocking the solution by making adds which are too large. You might try making your adds more often in smaller quantities.

Phil Pace
- Tulsa, Oklahoma

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