Metal finishing Q&As since 1989

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Silicon in electroplated zinc and yellow dichromate

2006

Hello,
My name is Jon and I work for a tier supplier to the automotive industry. Our customer is having welding issues where as the electrodes stick to the plated product and produces high arcing as well. Their electrode supplier suggested removing the silicon in the plating process but we are concerned about the repercussions this might present.

What role does silicon have in electroplated zinc and yellow dichromate. Our customer has inquired if we can remove the silicon due to they were told it is why their welding electrodes stick to the plated parts. Will this removal have an affect on the plating and/or salt spray requirements?

Jon Beck
Fastener supplier - Carol Stream, Illinois, USA

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First of three simultaneous responses --

Hi Jon,

Hmmm, to the best of my knowledge there shouldn't be any silicon present on a yellow zinc part after plating. I have heard that minuscule amounts of brightener components can be included in a plate, but I can't imagine silicon being one of these. It sounds like there is more going on here as this type of plating gets welded fairly frequently without this sticking problem.

Oh yes, there may be silicates in your cleaners, but if you are rinsing correctly they should not be present on the plating either.

Hope this helps

Trent Kaufman
electroplater - Galva, Illinois
2006

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Second of three simultaneous responses --

It is the other guy's fault! It does not matter who you ask. I really doubt that there is enough silicon in any plated material to cause a problem. That and the plating layer is so thin that it should not bother. Now, on the other hand, some steel and some aluminums have a lot of silicon. I would send a few pieces out to another welding shop and see if they find a sticking problem.

James Watts
- Navarre, Florida
2006

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Third of three simultaneous responses --

"What role does silicon have in electroplated zinc and yellow dichromate?" -- None (that I know of).
Ask for more info. Is a silicone sealant applied after chromating?
Is this stud or spot or other welding? Higher contact pressure and amperage & longer times are required for coated steel. Ask the welding equipment supplier for proper settings for chromated, zinc-plated steel. Periodic cleaning of zinc buildup from the electrode is necessary.
Some info & references on welding zinc-coated steel at www.welding-advisers.com/Joining-lead-tin-zinc.html

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2006

Although I agree with the previous three replies, could the user be talking about silicates? These would be contained in sealers used over the zinc plate and conversion coating.

Gene Packman
process supplier - Great Neck, New York
2006