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

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Resistance welding zinc plate trivalent chromate ring

We have recently changed from a hexavalent chromate to a trivalent chromate zinc plated ring retainer that is subsequently resistance welded with a ring electrode.

The ring retainer contains several small projections which melt and fuse to the sheet steel part after resistance welding.

My question- When resistance welding, is there a difference in electrical resistance between a trivalent chromate and a hexavalent chromate?

Graham Dodd
Automotive - Melbourne, Australia
2005

Your question is quite similar to letter 42062, Graham. Trivalent chromium conversion coatings tend to not be as corrosion resistant as hexavalent coatings, so topcoats (lacquers, waxes, sealers, silicates) are rather routinely applied to make up the difference--and these topcoats will generally significantly inhibit the conductivity.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

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