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topic 4853

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


Hi Aaron,

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

Kwok-wai Chook
Hong Kong, China


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


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
sara michaeli signature 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel


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

tim neveau
Tim Neveau
Rochester Hills, Michigan

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