Ask the Expert Question-and-Answer Archive

by Ron Joseph

January, 2009

Painting Aluminum Parts with Powder

Q. I work for a company that supplies a large number of Fans for the HVAC market and I am looking for a low cost wash option for a system originally designed for steel. We presently paint our steel parts in an e-coat system and in the event that a black color is required, we paint over the ecoat with powder. This allows us to have plenty of salt spray protection and an easy way to get that second color the customers seem to believe they cannot live with out. Our problem occurs when we paint aluminum Hubs and complete fans with steel centers and aluminum blades. the E-Coat wash system becomes contaminated when you introduce the aluminum into the chemicals used for steel cleaning. We are considering a chemical that would work for both aluminum and steel which may solve our problems, but in the mean time do you know of an easy way to wash these parts manually? I am thinking a wash booth with a pressure washer, or a conveyor type system with stages. If you have vendor suggestions I would be interested in that as well.

A. What is your current wash system? Are you using a chromate conversion coating for the aluminum? Probably the most effective system for both aluminum and steel is a phosphate wash and pretreatment that is designed for both metals. This is not as effective as conversion coatings specifically formulated for aluminum; however, such phosphate pretreatment chemicals are available from companies such as Henkel Surface Technologies and Chemetall Oakite. Many vendors are available to design and build a pretreatment washer system, and all of them can be found on the Internet. I don't have a particular recommendation.

Regards,

Ron Joseph