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Metal on Metal - Zinc Phosphate [Arkansas] 

April 5, 2008

We fabricate steel products and many times we have steel laying across steel. Our competitors use no kind of protection between the metals, they simply paint the finished product. subsequently rust will form and begin to bleed out. Would a zinc phosphate coating on both metals prevent rust forming in between the metals?

Steve Ashmore
Fabrication shop - Rogers, Arkansas, USA

Hi, Steve. Zinc phosphatizing is considered a quality pretreatment method for steel components. If you or your competitors are doing something less in terms of pretreatment, then zinc phosphatizing will certainly improve your product

The ideal treatment, but the most expensive, is zinc plating and chromating (or galvanizing), subsequently phosphatized, subsequently electrocoated, subsequently powder coated.

The least effective treatment is solvent wiping followed by painting. The first step up would be phosphatizing followed by painting -- but whether it is good enough to solve your perceived problem is hard to say.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Hi, Steve,

Selection and quality of pretreatment is tightly related including type of paint. It sounds you may need to review both yours and your competitors'¯ process to need your customer¡¯s need.

Jun Zhang
- Cincinnati, Ohio