Letter 2065

Corrosion

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I work in a plating shop. We have a zinc chloride bath. We are have problem with welder parts, with rust. We have found that between the to parts salt is present. Do you have any idea how to fix this problem? any suggestion will be appreciated

Rafael A Dominguez

If I understand you, solution accumulates in the seams of the parts and causes corrosion. One of the best ways of removing it is with alternating hot and cold rinses. A technique often used in anodizing, and which may be applicable for you, is to try to displace the process acid with a dilute solution of nitric acid; in as much as a nitric acid dip is a good preparatory step for chromating, perhaps you should employ it if you are not already.

If the acid cannot be removed from the seams with hot & cold rinsing or nitric acid, then you can keep it out of the seams by filling them with anerobic sealant before plating. I understand that this technique has been used on computer chassis, so you may be able to find an IBM spec for it.

 
Ted Mooney, P.E. - finishing.com inc. - Brick, NJ

I've just learned about a microbial organism that's present in certian well waters. If during any process of your plating the iron is introduced to non treated well water the organisms can be introduced and corrode the weld area in the heat affected zone of the weld.these organisms have been found to corrode nickel,stainless (304&316), as well as carbon.

James Tullos

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