Ask the Expert Question-and-Answer Archive

by Ron Joseph

January, 2003

Acid-Etch Resistant Paint for Aluminum

Q. We are looking for a paint type that is acid-etch resistant for painting 6061-T6 aluminum. The paint must be resistant to NAoH (sulfuric acid) and not leave stains once the liquid is crystalized and wiped clean either with Alcohol or warm water. Paint must be matte black. Any advice you can give is appreciated.

A. Without knowing more about your product or the conditions under which it will be used, I can only give you a generic answer.

First, you need to tell me about the surface preparation of the aluminum. Will you be providing a chromate conversion coating, such as Alodine, or do you intend to paint directly to the aluminum? Adhesion of paint to the substrate is critical and you need to attend to that before anything else.

With regard to the coating system, you will probably find that an epoxy primer MIL-P-23377 or an equivalent will work well. Unless you are in need of a very highly acid resistant coating, you might want to evaluate a polyurethane, such as MIL-C-83286.

Please do not take my advice until you have actually tested the system under similar exposures conditions. If the polyurethane doesn't provide sufficient resistance you might want to evaluate a true vinyl coating. Finally, the choice of a system will also depend on the paint facility and equipment that you have available for painting large quantities of these items.

If you need further advice and need to conduct laboratory tests to validate your selection I will be willing to assist you on a consulting basis.