Pretreatment of Aluminum for Powder Coating

Question:

What is the best way of treating aluminum before powder coating? How can we protect the phosphated parts after phosphating? A.A.

Answer:

One of the best and most widely used pretreatments for powder coatings or liquid organic coatings on aluminum is a 5- to 7-stage cleaning and treatment with either chrome phosphate or chrome chromate. The sequence would go something like this:

• Alkaline or acid clean
• Rinse
• Rinse
• Chrome phosphate or chromate
• Rinse
• Rinse (DI water)

Perhaps the best way to protect the pretreated metal prior to coating is to cover it with a tarp or plastic (visqueen) to keep the dust off. Material pretreated during one work shift should be coated within that shift or during the next shift. Wait any longer and the surface can become contaminated with dust and other airborne debris, degrading some of the advantages of the pretreatment, namely adhesion and smoothness of the coating.