Painting Anodized Aluminum
Q. We provide powder coating to a company that does stadium seating, scoreboards, gymnasium equipment, etc. They have a job where a top rail of a stadium will be of anodized aluminum (not sure of the specific process used to anodize) and they wish to powder coat in an orange color. Can you tell me the pros and cons of painting anodized aluminum? Do you know of companies that powder coat such parts? J.P.
A. Anodized aluminum can be effectively powder coated. There are different aluminum alloys, and anodizing can be done with different acids. Adhesion over some anodized parts can be a problem, so you should confirm that this is not going to be a problem for your parts. Be sure that the surface is clean and free of dust, dirt or oils.
Run a sample part and perform a wet adhesion test. Cut the coating in a cross hatch pattern in accordance with ASTM 3359. Put the cut panel in boiling de-mineralized water for 20 min. Remove, dry, cool and do the normal tape pull test.
If you pass this test, it is a very good sign that your part is clean and ready for the powder.
Masking is employed in most any metal finishing operation where only a specifically defined area of the surface of a part must be exposed to a process. Conversely, masking may be employed on a surface where treatment is either not required or must be avoided. This article covers the many aspects of masking for metal finishing, including applications, methods and the various types of masking employed.
Powder coating is one of the most durable finishes that can be applied to industrial manufactured products, and offers excellent corrosion protection and is very safe because of its lack of volatile organic compounds.
Metal fabricators that laser-cut with oxygen take steps to prepare parts better for powder coating.