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Tin/Zinc Plating with Black Chromate Treatment

I received a military print for a small plain carbon steel, stamped part. The part will be heat treated to 32-40 HRC and the print calls for Tin/Zinc plating per WSE-M1P93-A1 with black chromate treatment. My Tin/Zinc plating company out of Chicago claims a black chromate treatment to a Tin/Zinc plating is impossible (or at least not done). Is this true? Any help would be appreciated.

Regards,

Ryan Nelson
- Oklahoma City, Oklahoma
2002

Tin-Zinc with a black chromate is not normally done. There are some chromate products just released to the market that we will be testing in our lab very soon. We also have some tricks that can produce Tin-Zinc black now.

Andy Scheer
- Pacoima, California, USA
2002

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2007

Tin-Zinc colors currently are yellow and white (clear). Any black, green or whatever is not possible with one exception:

Some people want their finish of tin-zinc to look as nice as regular zinc. What some platers are doing is to "strike" or "flash" a coating of traditional zinc over the tin-zinc. Then they apply a regular zinc chromate of yellow, blue (or whatever) on top of the zinc strike.

Now, the product has the protective coating of tin-zinc, with a very fine layer of traditional zinc, followed by a traditional zinc chromate conversion coating with the color or their choice. The green or O.D. dye color could also be added on top of the zinc strike plating.

The downfall to this is two issues. One, cost goes up even more with a zinc strike applied. Issue #2 is that if one is following a tin-zinc spec (like Ford's for instance), adding the zinc strike coating on top of the tin-zinc may bring the plating job out of spec. It may also add other problems which are too long to get into here on this forum.

Roger Fasting
- Sacramento, California, USA