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Sealer after powder coating?

Q. Hello,

This is my 2nd question to this site. Thanks everyone for the help on the 1st question (20391).

The problem I have now is in the design of the part that I am coating. There is about a 1/8 inch gap about 1/2 deep that I can't get the powder into. After coating the part and setting the part outside for couple days I notice the part will start to rust inside this gap.

Is there some kind of sealer that I can dip my part into to seal up any of these types of spots after coating?

Thanks again Ron

Ronald D Flahart


A. Hi, Ronald. I reviewed your 1st question and note that you were having an adhesion issue. Taking your two problems together I'm beginning to suspect that perhaps you aren't doing any pretreatment. You need to phosphatize before powder coating both for adhesion and corrosion resistance; and if the parts are to be used outside it really should be zinc phosphatizing. This will not totally prevent rusting but will make a big difference in corrosion resistance, as well as promote adhesion.

Please describe what you do to the metal before powder coating it. Thanks, and good luck.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

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