Painting coroplast smooth covers

[Bicycle Bob]

Coroplast is polypropylene, one of the waxy plastics, but it is used extensively for signage, so the factory gives it a "Corona Discharge" treatment to enhance adhesion. When you break open a fresh bale of the stuff, you get sparks like taking off a wool sweater in a dry room. I have seen a piece of it that lay on the ground for months still attract paint from the end of a pointed artists' brush from a short distance, producing an effect like a weak airbrush. However, I'm also having major flaking problems on a re-painted piece. So, it might be back to the sign shop for some vinyl wrap, which can be printed to any hue.

[Grant-53]

Check the Coroplast website for their recommendations. Also check with the local auto body paint suppliers. If you want, switch to ABS plastic which is used on auto fascia. Light sanding, 400 or 600, clean and tack rag, light primer coat, use automotive basecoat / clearcoat acrylic enamel or an industrial grade enamel. White rubberized undercoat can be painted over for abrasion resistance. Use a respirator and down draft paint booth. A large box and a shop vacuum vented outside will do. A heat lamp might be handy as the ambient temperature drops below 70 F.

[KamperBob]

I don't have any first hand experience to share. But, once upon at time I read somewhere, possibly (probably?) on this forum, about folks gluing pieces of coroplast together. The tip was flashing the surface with a flame torch to break down some kind of coating. Just enough for that, not warping the coro, so scrap practice seems prudent. Maybe it's a UV protective coating? Then it was gluable. I'm thinking chemical adhesion here. Mechanical adhesion by sanding only maybe at play with some paint flaking anecdotes.

Another thought: election signs. Find some place that does that kind of printing. Maybe they'll share a nugget or two of experience about making coroplast hold colors.