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Uneven plating thickness in acid zinc

Q. We have acid zinc plating line in house. The issue is the plating thickness is very low for one side of the rack and other side has very high for the same rack. What factor causes it and how to fix it?

Elaine Shen
- Menominee, Michigan, USA
October 3, 2018

A. Hi Elaine. According to Faraday's Law the thickness of the plating is directly proportional to to the current flow to that surface. Thus you apparently have very low current flow to one side and very high to the other side.

Is the rack centered between anodes so the back of the parts are roughly the same distance from the anode as the front of the parts?
Is it possible that the anode rod on the one side is "dead" due to a poor connection somewhere? Have you tried a voltmeter from an anode on one side of the rack to the parts, and from the anode on the other side of the rack to the parts?
Another possibility is that you are expecting too much. Fairly wide variation is not unusual.

Try to get us some numerical facts. Thanks.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 2018

plating in Mexico

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