Metal finishing Q&As since 1989

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Neutral salt spray resistance for zinc plating with clear passivation

We have analysed a component plated with Zinc plating and clear (blue) passivation for neutral salt spray as per ASTM B117 and didn't find white rust even after 450 hours. Is this possible? What are the factors make this different?

Narasimhun Parthasarathy
auto electricals - Chennai, Tamilnadu, India
2006

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First of two simultaneous responses --

Any thing is possible, at least on a one time basis. Assume that it is a thick coating that has been very well done with an excellent blue chromate and has been handled with care.. My real guess is that they put a very thin coat of clear lacquer or wax on it.

James Watts
- Navarre, Florida
2006

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Second of two simultaneous responses --

Dear Mr Parthasarathy;

Yes its possible with a combination of Alloy Plating, amazing chromate products and really good topcoats.

My plating shop commits 250 hours to white rust for Zinc but delivers much more!

best regards,

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2006

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2006

1. I would check all the operating parameters of the salt spray cabinet.

2. 450 hours can be reached with a zinc alloy (zinc cobalt/iron/nickel) with an organic sealer on top of it.

Sara Michaeli
Tel-Aviv-Yafo, Israel

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It is a Zinc plating with clear passivation having thickness of 10-16 microns. And please let me know the methodology to find out the presence of topcoat or sealant by any instrument/chemical test?

Narasimhun Parthasarathy
autoelectricals - Chennai, Tamilnadu, India
2006

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