Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2004

Painting Over Polished Aluminum--Poor Adhesion

Q. What is happening in the process of "polishing" aluminum that causes very poor adhesion of paint? What can be done to overcome this while maintaining the mirror-like finish?

Thank you for your e-mail. Paints generally do not adhere well to untreated aluminum surfaces because a microscopically thin aluminum oxide film is naturally formed when aluminum is exposed to air. The oxide is relatively inert and is difficult to remove except by abrasion and/or contact with very strong acids. The oxide forms almost immediately after the virgin surface is exposed to air; therefore, even if the oxide is abraded off, an new oxide will form quite quickly

When aluminum is polished it is possible that polishing pastes are used that remain on the aluminum service after the job is done. If so, they will also detract from adhesion of the coating to the substrate.

I hope this explains why you are experiencing poor attention.

Best wishes,

Ron Joseph

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