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Powder coating peeling off Galvanized

I have a customer who is having problems with the powder coating bubbling, peeling off window frame's used on large trucks. These are aluminum frames and it looks to be oxidizing under the coating. the problem seems to be more noticeable on the outside where it get the full weather affect. I have informed the customer that we do not have this problem with other customer who are coating other substrates, such as cold rolled steel. I have informed him to look at his pretreat process, especially when it comes to galvanized. I am looking for any information that I can use to help put them in the right direction.

Thanks,

Mark Hendel
- Grand Haven, Michigan

I think you are on the right track in having them check their pretreatment process. What kind of pretreatment are they using for the aluminum. Also apparently they are coating over galvanized & this raises a new set of issues to be dealt with.

Eric Beeson
- Hastings, NE, U.S.A.

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I am not sure how you equate aluminum and galvanize together in this circumstance. I too presume that this may be a pretreatment problem. I believe that most likely, you have pre-oxide on the part and it was not eliminated within the pretreatment system. If you have this "white" oxide on your parts, it helps considerably to use a floridic cleaner to help clean off this oxide. Make sure also that you do not apply any coatings over smut or moisture since this will enable any oxide to grow and creep or bubble. Double check that you are rinsing with very pure water before drying so that no residual contamination remains upon the part. Also, make sure that your topcoat is properly cured.

Bob Utech
Benson, Minnesota