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Spots appear on zinc plating after 48 hours under normal environment

April 21, 2010

Base metal is 4130, with zinc plating. Being put in stock in plastic bags for 2 or 3 days, corrosion spot appears on the surface. Other parts were plated at the same line does not have this problem. Even several replatings can't solve this problem. Cyanide plating bath, 8-10 µm thickness, Pavco trivalent chromate. The parts were replated at another plater, alkaline plating bath, 10um, Yuken trivalent chromate, but with same issue. What is the root cause?

Sharon Luo
Supplier chain - Shenzhen, GuangDong, China

First of two simultaneous responses -- April 23, 2010

Pitted parts, cold shuts and bad alloy comes to mind.

James Watts
- Navarre, Florida

Second of two simultaneous responses -- April 26, 2010

Is it a cast iron, may be its too porous, I would suggest to have an acid zinc plating, then heat it and then passivation followed by a silicate sealant.

Hope this would help to achieve better corrosion protection.
Best Regards

praveen kumar
Praveen Kumar
plating process supplier
Mumbai, India

April 26, 2010

Sounds like you are plating castings to me. Correct?

Trent Kaufman
Trent Kaufman
electroplater - Galva, Illinois

April 28, 2010


What happens if you do NOT bag the part? Are the parts dry when you bag them? Have you tried a different supplier of bags, or material? Do you bag other parts without issue?

Willie Alexander
- Colorado Springs, Colorado

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