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Using alumina in parts washer as an adhesion-promoting pretreatment

My company is currently having issues with adhesion using powder coating on a certain product. I don't want to use chemical means but I heard grit blasting is a fantastic way to promote adhesion sites mechanically. The only problem is I don't have a grit blaster so I was thinking of adding 50 micron alumina powder to a power washing system to use as a pretreatment for the part. Will this work or be more detrimental to the washer than anything?

Allister Lobo
Analyst - Toronto, ON, Canada
March 14, 2011

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Hi, Allister.

I haven't heard of using an abrasive in a parts washer, but I suspect it would rapidly wear out the nozzles, piping, and pump. But please study phosphatizing before deciding to do without it. It serves important functions besides adhesion promotion, including deterring undercutting, preventing filiform corrosion, neutralizing galvanic hot spots, and providing a little bit of self-healing.

Grit blasting can be good for certain precision plated parts because electroplating is a metal on metal process. It can be much less effective as an adhesion promotion method for powder coating on galvanized metal, powder coating on brass and copper, etc.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 15, 2011