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How does zinc plate with chromate or bright chrome finish perform in hydrogen sulfide?

May 29, 2008

Hi
I am working on the design of a product that is to be used in environment exposed to both dry and wet hydrogen sulfide. The fasteners used are case hardened steel and the manufacturer offers zinc plate with chromate or bright chrome finish. Would anyone know how those two types of finishings perform in those situations?
I looked into using stainless steel like 316 before but the cost a lot higher than the regular finishes.
Thanks very much in advance.

Tom Li
product designer - Kitchener, Ontario, Canada

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May 30, 2008

Hydrogen sulfide can form several different acids with water and oxygen and are very corrosive, especially as the temperature goes up. I think that you would be better served with a high phosphorous electroless nickel than chrome. Zinc is an absolute no-no.
You need to watch the quality of your plater very closely to not have problems. I would be very cautious of a shop that was significantly cheaper than several others. I would want to be comfortable that they had a good quality program and actually followed it, and not just certified to it.
Depending on size/shape and machining problems, 316 might be the better way to go, and it might not be the best SS for the job.

James Watts
- Navarre, Florida