Flexible Paint

Q. I need to paint steel parts and form them later. Can you recommend a paint type that is flexible enough to adhere after bending? My parts are small, made from 1-inch-OD thin wall tubing. The tubing is compressed laterally and budges outward, forming a “V” on either side. The parts will be plated and painted, and then formed after painting. We are looking for a flexible paint that can take the forming without fracturing.

The tubing material is mild steel with a zinc-nickel coating that has some very slight micro cracks. The flexible coating also will need to be resistant to galvanic corrosion, as the parts will be used outdoors. —D.C.

A. My concern is the micro cracks in the ZnNi plating. If the cracks open up, they may cause the paint film to rupture. Several of the more-flexible paints have poor adhesion when used direct to metal. They would require a primer, while others would require pretreatment of the plating to obtain adhesion. In either case, that would add an extra step to your process.

Paints based on polyvinyl chloride, certain polyester, epoxy polyamide, amine cured epoxy and dicyandiamide-cured epoxy resins would have sufficient adhesion and flexibility for your application. All of the epoxies would chalk in direct sunlight, however.