Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

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Does nickel coated 302 SS wire need to be passivated to avoid corrosion

Is nickel coated 302 SS wire more resistant to corrosion in a salt spray test, than 302 SS with a soap coat finish? How long will nickel coated 302 SS last in a salt spray. Does it have to be passivated to pass a salt spray(120 hrs). I would like to skip the passivating process. Is there anything I can do ? and keep the parts from rusting?

George,

The 302 Stainless wire is typically coated with a non-oil lubricant to aid in the wire drawing operation. Some wire manufactures use nickel, but most use a soap coating.

Also, springs are typically shot peened after coiling to improve fatigue life of the spring. Check to see your springs are being shot peened? The media and equipment need to be reviewed. Standard steel shot will leave free Iron on your springs and cause rust. To avoid the issues of free iron & the need to passivate after, you can use Conditioned Stainless Steel shot Instead. Just ensure the shot peen media and equipment are cleaned out of any steel shot before using Stainless steel shot.

If corrosion resistance is your concern, together with keeping the springs properties, you should look at thermo diffusion zinc coating. There are several companies that I'm familiar with.

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