Letter 485

Can I skip the chromate on zinc plating

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Actually we have a system enclosed in a box made of steel plated with zinc and yellow chromate. After I did some testing I found that the chromate doesn't offer good conductivity. That doesn't make a good shielded box.

If we only apply zinc with no chromate the finish is very conductive but I was told that corrosion could occur rapidly. Is it right ?

I'm looking for a finish or coating that

protect steel from corrosion
could be painted ???
is very conductive
relatively low cost

Could you help me or refer me to a company.

Best Regards

Francis Pelchat -
St-Léonard, Québec - Canada

Did you try "blue" or "clear" chromate - it is much thinner, therefore more conductive.
You should not be afraid of corrosion - Zinc with or without chromate provides almost the same degree of protection to steel. Without chromate your finish is easily fingermarked though and will show Zinc corrosion (white powder)much sooner than with chromate.

Max Stein
Montreal, Québec

Max is right, blue passivation is the correct answer. If blue is still not good enough, try a short dip in 0.5% nitric acid. The nitric deos not improve white corrosion resistance but gives a better appearance.
Sara

Sara Michaeli     chemical process supplier Israel

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