Blemishes on Zinc plated carbon steel 2

[Hercules28]

Hi,

I am evaluating a new supplier and I saw black blemishes on zinc plated carbon steel. I suspect it has to do with pre and postcleaning the parts. See attached pics.

Any similar experiences?

Thanks,

Herc

 

[CoryPad]

Blemishes like that do occur and inadequate pre-cleaning is a common cause. If the parts are acid pickled prior to plating, maybe there was some smut remaining on the surface prior to plating.

 

[Metaljon]

The usual cause is carbon contamination. Excessive carbon on the surface of the substrate will greatly decrease the overall adhesion of the zinc deposit. Proper acid pickling treatment or anodic cleaning will greatly reduce or even eliminate the formation of carbon on the surface.

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