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Chrome 3 vs. Chrome 6: Different coefficient of friction?
February 11, 2014
Q. Hi all,
Am encountering a friction problem and can't seem to understand where it is coming from. We have recently changed surface treatment from Cr6 to Cr3 but this has a secondary treatment which is Zn-Ni and is the same in both cases.
Does anyone think that the difference between the Cr6 and Cr3 under the Zn-Ni coating have any potential effect on the coefficient of friction of the finished product.
A. Hi Andy. 99.9% of the time the coating sequence would be Zn-Ni electroplating followed by Chrome 6 or Chrome 3 chromate conversion coating (passivation). And even if you did electroplate Zn-Ni on top of chrome plating, again 99% of the time it would employ a chromate conversion coating on top of that.
So I am suggesting that you investigate whether the situation has been transcribed to you correctly because, while anything is possible, it sounds likely to me that the process description became confused somewhere along the line.
Please try to explain the situation behind the friction problem and I'm sure we can do a much better job for you than if it's all kept abstract and intangible. Thanks.
Ted Mooney, P.E.
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