Powder Adhesion to Anodized Parts

Q. We are having problems with powder coating adhesion on parts that are black anodized prior to powder coating. Are there any inherent problems with powder coating over black anodized aluminum parts? Is it better (or possible) to black anodize after powder coating? S. P.

 

A. Parts that have been anodized can be powder coated successfully with certain precautions. First the aluminum has to be cleaned after anodizing using at least DI water to remove salts or complete cleaning using a three-stage cleaning process to remove handprints and soils accumulated during shipment and storage. The three-stage process should be a cleaner/coater followed by a rinse and a DI rinse. If the part is very clean, then the powder coating will have good adhesion. Of course, the powder has to be applied evenly to an appropriate film thickness (1.5–3.0 mils) and fully cured to provide good surface wet-out and adhesion. You can forget about anodizing after powder coating, as this is impossible. Good luck.