We do electroforming using nickel sulfamate plating baths. Lately one of our baths is giving us a much brighter than normal deposit. We are not adding any brighteners to the bath. What might be causing this? S.F.
I have heard of a few cases of this happening. Although you say you are not adding any brighteners to the bath, might you be adding something to improve the hardness of the plate? Sometimes cobalt sulfamate is added for this purpose, and the cobalt will complex with impurities in the plating bath giving a brighter deposit. Another possible cause for this is the breakdown of the sulfamate in the plating bath. This tends to be a slow process but over time it can generate enough breakdown products to cause a brightening effect.