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Why do we have scratching on Zinc-Iron plating with black chromate?

Need help with problem, tried everything but I am still getting scratching on the parts with zinc fe and black chromate with sealer; customer rejecting the scratching. How can I solve this problem or what is causing this issue
thamks

Mark Banspach
plating shop - Providence, R.I.
2005

First question is do you get scratching of sealer or chromate? Second: are parts chromated and sealed in barrels, baskets, racks, etc.? Third how are parts dryed and at what temperature? Fourth: How are parts handled and shipped?

Gene Packman
process supplier - Great Neck, New York
2005

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2005

Hi!

Try to increase Iron level in the bath to the highest level that is suggested from your supplier.
Analyze bath on carbonate, when it is over 80 gpl, than dilute the bath on half, or get rid of carbonate by cooling down the bath on 4-5°C. Carbonate (an also a lot of caustic) will pecipitate.

Dimitrij Us
- Kranj, Slovenija (EU)

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Dear Mark,
Check the pH of the black passivation bath and adjust as per suppliers manual. Use deionised water for rinses.
Please give more detailes about the process cycle you follow.
Good luck

T.K. Mohan
plating process supplier - Mumbai, India
2005