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topic 4541

Black EN


(2000)

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


(2000)

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


(2000)

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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