Metal finishing Q&As since 1989

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Zinc plating peeling/blistering off

2006

I had several parts (machine doors) which I found some peeling/ blistering around/ near the internal curvature portion.
note: the door material is steel and it was blue zinc plated and after that it was
sent for powder coated on one of the external surface.

please advise what is the possible cause of the peeling/ blistering of zinc plating at only surface near the curvature area?

Elvin Tan
Contract manufacturing - Singapore

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The peeling/blistering is probably due to high internal stress of zinc deposit at curvature area which is considered as high current density region compare to flat area.

David Shiu
- Singapore
2006

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2006

Mr Tan

When you state " Internal Curvature Area " we presume this is the INNER part of the door where possibly the steel is bent at a 90 Degree angle.

If this is really the case the possibility of lack of zinc deposit in the Lo Current density are may exist.

Secondly, a blue chromate is usually less thicket than a Yellow chromate and absorbs less paint which can sometimes become a cause of paint peel off.

Most plated components that go for Powder coat or paint use a HEX yellow or a TRIVALENT green thick film coat.

Both are thick and paints adhere well.

Hope this helps.

Asif Nurie [deceased]
- New Delhi, India
With deep regret we sadly advise that Asif passed away on Jan 24, 2016

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2006

Hi there,

I would recommend zinc phosphating before powder coating.

Regards,

Dominik Michalek
- Mexico City, Mexico