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  for Metal Finishing since 1989
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Yellow vs. Black Chromate

I simply need to know which will last longer in a continuous salt spray test, a steel part coated with zinc/yellow chromate conversion, or one coated zinc/black chromate conversion, or does it make any difference?

Aaron Acton
- Westfield, Indiana, USA
2000

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Hi Aaron,

From my understanding, black zinc chromating can last longer in salt spray test. Regards.

Kwok-wai Chook
Hong Kong, China
2000

Should it be the other way around that a yellow/iridescent chromate conversion coating last much longer than a black chromate on electrodeposited zinc at a standard 5% salt spray test?

S. Y. Yuen
- Hong Kong, China
2000

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The yellow lasts longer - 96 hours in 5% ss. But if you are really looking for a long time in SS, try a zinc alloy like zinc iron with black chromate (no silver needed) ,zinc cobalt or zinc nickel.

Sara Michaeli
Tel-Aviv-Yafo, Israel
2000

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I have done many salt spray tests on both. My vote is for yellow!

Tim Neveau
Rochester Hills, Michigan
2000