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Assistance with tech. question concerning standard Zinc plate yellow chromate

2004

I need some anwsers about Zinc plate Yellow chromate finish. i.e., GM 4344M 6D96/48.

How many days after the finish is applied, is the part fully cured ?

Is there a finish hardness diffrence on day one compared to day 14 ( after finish is applied) ? Does heat to the finish change or distort the finish ? If so what tempatures, and what does it do to the finish ? Will this tempature to the finish change the salt spray protection of 96/48 ?

How can someone tell if the processor skipped the required bake cycle required for this spec ?

Dan Lubera
- Chesterfield, Michigan, USA

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Yellow chromate on Zinc ( or aluminum) require at lest 24 hours to cure. There may be a small change in the 14 -day period you mention, but not very significanat. Heating above 150 °F will dehydrate the protective film. The result is loss of salt spray protection, and loss of the self healing properties of chromate conversion coatings.

Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
           and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])
2004

Standard Process would be to Plate part as you normally would except dry good with out chromate, Bake for hydrogen embrittlement the chromate or brite dip in .5% nitric acid and chromate (of course all the rinse's) depending on process, how well parst are pre-dried and and there may be some dullness to the parts

Chris Snyder
plater - Charlotte, North Carolina
2004