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Reverse Etch for Hard Chrome
Q. Hello All,
I am a hard chrome plater in Ontario, Canada and have a couple questions about reverse etching and bath contamination. My hopes are to reduce the amount of amperage or time (or both) of the reverse etch operation to reduce the amount of iron contamination in the bath.
Across our company we use a couple different reverse etch times and amperages and I was wondering if there are guidelines to follow to ensure chrome adhesion.
We have an ECM (electro-chemical machining) operation which proceeds the plating line. Shouldn't this acid+current operation essentially do the same as reverse etching within the plating bath?
The parts do sit for up to one week between ECM and chrome plating. My guess is that if we eliminate this sitting time we could reduce the reverse etch times/amperages.
Are there any suggestions on how to reduce the reverse etch times/amperages to reduce the iron contamination?
Hard Chrome Plating - Guelph, Ontario, Canada
A. One way we have used when hard chrome back-etching is to have a bath specifically for back-etching and then moving immediately to the plating tank. Not ideal but does prevent excessive contamination with iron.Brian Terry
Aerospace - Yeovil, Somerset, UK
Thanks Brian. That would actually work out quite well. Our alternative to reducing iron contamination is to purify it with either porous pots or a CrPur system. Even if we did decide to purify the baths, it would be MUCH easier to do so on one tank rather than eight.
- Guelph, Ontario, Canada