Limiting Galvanic Corrosion, 302SS & ZnNi Plated Steel
What are options for limiting galvanic corrosion between 302 ss and Zn Ni Alloy plated 1038 steel? Increase steel plate thickness? Barrier coat the stainless (ie, electroless nickel)?Myron Clark
Stanfield, North Carolina
I'm not sure if you are reporting an actual problem, Mr. Clark, or a theoretical concern. In general, you specify the ZnNi alloy plating because you WANT this coating to exhibit a galvanic potential to protect the substrate.
The environment the item is exposed to is important; if it's clean and dry, you probably have little cause for concern. The second subject to consider is the relative surface areas of the ZnNi vs. the stainless; again you probably have relatively little cause for concern if the surface area of the active material, the ZnNi, is large compared to the area of the stainless.
But if the environment is wet and these are small ZnNi plated fasteners on large stainless steel items, you are probably right to be concerned, and the most effective thing to do might be to use plastic bushings and washers so the fasteners don't touch the stainless, or to paint the stainless so the exposed galvanic area is small.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
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