Letter 38018

Chem film vs. phosphate wash for adhesion of powder coat [Washington] 

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Is there a research or chemical reference for the properties of chem film vs. phosphate wash for prep of aluminum and resulting adhesion qualities of the powder coat to the aluminum? Is one better than the other? If so, which is best and why?

We have a powder coat line in our sheet metal fabrication plant and have been asked if the chem film step is necessary. I'd also appreciate knowing if anyone has any adverse experience with lack of adhesion using just a phosphate wash for prep of aluminum prior to powder coating.

Thanks.

Fred Brown
L&M Precision Fabrication, Inc. - Washington, USA

Both methods are acceptable. Unfortunately, which one is best is rather dependent on which operator/company is doing the work.
Then, you get into "best" from what standpoint. Added corrosion resistance, adhesion, speed, cost, level of abuse and storage among others.

James Watts
- FL

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