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Strong Zinc-Coated Passivation

2006

Hello,

I am a chemistry student in work placement for an engineering firm. Due to recent specification change from our customers, we need to find an alternative passivation to the automotive zinc-coated parts we provide them with. We now need two different passivates :
The first needs to be cheap, free of Chromium (VI) and needs to last 72 hours under salt spray test.
The second requires a much stronger result under salt spray - 240 hours with less than 10% red corrosion. It also must be free of Chromium (VI).

Both must resist to temperatures of 200 °C.

I have looked around for days and called many companies offering passivation solutions, but due to the complexity, I would rather speak with people who have the technical knowledge to advise me.

Thank you very much.

Quentin CAUDRON
Automotive - Durham, UK

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2006

Hi Quentin,

The Guys you have been speaking to are probably the best chaps to advise you if you are not well exposed to the field. Continue talking to them and use their advice.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

If the companies developing and supplying the passivates to the finishing industry don't have the technical knowledge to discuss the situation with you then how do you expect to get the answers you seek on a forum like this?

John Martin
- Wales
2006

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2006

Dear Quentin,
You can use Cr(III) blue passivation for 72 h salt spray test, and you can use Cr(III) yellow passivation that gives 300nm thickness passivation for 240 h salt spray test. I know all electroplating chemicals suppliers have these products. Cr(III) yellow doesn't give yellow color, you shall know this. It gives green-pink color, but we say yellow because it has similar properties like thickness and corrosion resistance with Cr(VI) yellow passivation. If you search chromiting from net you can find lost of information.
Best regards,

Pinar Yilmaz
- Turkey