Powder Coating Over Rust

Ask an Expert From: Products Finishing, from Powder Coating Consultants, Div. of Ninan, Inc.

Posted on: 6/1/2005

Question: I’ve just returned from a new (small) powder coating shop in Canada.


I’ve just returned from a new (small) powder coating shop in Canada. It’s very basic with no “tanks” in place. The steel parts are Phosphate “power” washed using Fremont 658. Then “Hot” tap water rinsed. The parts are placed approximately 25-feet away from the power wash booth and hang-dried prior to powder coating. The wash booth has no “doors” on it and the next power washing casts a large moisture cloud into the room. The hanging parts immediately start to “rust.” The powder coater doesn’t have a concern. I do because these parts are part of a system that sells for $50–80K !!! Do I have a reason to be concerned? R. D.


Powder coating over rust is a bad thing. The rust will eventually bleed through the coating when your part is exposed to moisture. Eventually the coating will delaminate and fall-off your part. Considering that your product is very expensive, I would guess that your customer would not like their paint job rusting quickly after they purchased your product. Remember that the coating is the last thing you do to your product, but is the first thing the customer notices. It establishes the value and quality of your product. You have only one chance to make a good first impression. Having your customer see rust bleed through your paint probably isn’t the impression you are trying to establish. If your coater is not willing or able to correct this problem, go elsewhere for your coating services.


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