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Zinc Phosphate - Lubricity

I'm an engineer with a small bearing company and have done some steel analysis on some of our competitors products to do a study on material and process differences between our products. One of the items that came back on on the outer race was that it had a very very thin layer of zinc phosphate on the race. The chemical analysis company who did our testing stated that it may have been used for lubricity. I can not find any data to back-up this statement. I was wondering if anyone here has ever heard or has any insight to this dilemma.

Steve Williams
Product Design Engineer - Grand Haven, MI, USA
November 3, 2008

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Hi, Steve. The analysis is probably correct. Zinc phosphate is sometimes applied to such parts and then they are oiled or waxed to somewhat deter corrosion, and to lessen the tendency to gall in the press fitting operation. Manganese phosphate is a heavier phosphate coating that is used for similar and somewhat more severe applications. Internal engine parts and other machine parts are often manganese phosphated to avoid metal on metal contact before oil can get to the parts.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 3, 2008