Mitigating Peeling of Powder Coating on Thick Aluminum

Q: I have been in the powder coating and anodizing business since 1998. We are experiencing the peeling of powder coating on thick aluminum profiles of about 3 mm thickness or more. We follow the curing schedule in a calibrated oven with a temperature tracker and chromate pretreatment. Generally, dark colors like RAL 8016, 1303 and 9007, etc., have a tendency of peeling on the thick profiles. Can you offer some solution?

A: Thank you for the question. I would start by eliminating possibilities. First, check the powder for complete cure. Take a known sample — a small test part — that has been coated and cured to specification. Then check solvent resistance as a measure of cure. Use acetone or a similar solvent. Next, check adhesion issues. Take a very clean test part and abrade the surface with sandpaper or Scotchbrite. Thoroughly clean the surface with solvent and run through your chromate system. Run one clean part without the chromate as well. There may be something amiss in your chromate system. Also, check your coating thickness. Is it abnormally high? Too thick may cause adhesion issues. You may also try another powder or powder supplier.