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Chromate degradation caused by perspiration?

This is something I've never run across before. We are a distributor/supplier in the plating industry, and a customer has a situation I'm not familiar with. They zinc plate parts and coat with a clear chromate. These parts are then assembled at their customers facility. They had a problem with the chromate being damaged/removed, but the problem only comes from one assembly person. This person sweats profusely, and is on a regimen of dietary supplements, including energy drinks, vitamin C in large qty, and herbal supplements. My question is, has anyone out there experienced this phenomenon before? Is there any validity to this, or is it coincidence? Would sweat itself degrade a chromate film?

Kirk Jansen
- Portland, Oregon, USA

I don't know of any studies on that but I do think that people assembling chromated parts should be wearing gloves.

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

First of two simultaneous responses.

I do not know of any study, but from personal experience, I have seen one person that was so bad that a freshly ground piece of too steel would rust in less than half an hour wherever he touched it. He could remove yellow chromate with more handling and a longer time. My wife used a hand lotion that would remove the chromate coating from zinc and cadmium parts in seconds.

James Watts
- Navarre, Florida

Second of two simultaneous responses.

I too would suggest that anyone handling chromated parts should wear protective cotton gloves. The idea of perspiration attacking the base article is interesting and quite possible, but the rate of attack will depend on the thickness of the chromate passivate. It will also depend on the potency of the perspiration. Generally perspiration comprises lactic acid, other organic acids and various salts including sodium chloride, but when people start taking supplements, these can alter the chemistry of perspiration; people who eat a lot of garlic often find their perspiration also has its odour. The important thing will be the chloride ions, as these may be able to permeate the chromate film and attack the base zinc. You may even be able to see the attack in the form of fingerprint - induced corrosion on the zinc.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

This is so un-PC (politicaly correct)but many years ago the printed circuit board people noted that some women during the monthly cycle would corrode copper faster.
It was a theory among others for a random tarnish problem on copper. They could not single out this group of the work force so all had to wear gloves.

Jon Quirt
- Minneapolis, Minnesota

This one is just tooo....Well, come on, what is sweat comprised of? Water and salt? Among other things? Of course sweat will corrode even the best zinc plated parts. Ever see what it does to Stainless? Aluminum? Bare steel? Always wear gloves when handling parts both before and after processing.

Bill Grayson
- Santa Cruz, California

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