Painting ABS and Other Plastics

Q1. I need to paint black thermoplastic parts with white paint. Do I need to clean and sand them before painting? J. G.

Q2. I want to paint ABS parts. What types of paint will adhere to the surface? Do I need a primer? Do I need to sand the surface before solvent wiping? Z. A.

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Q3. I’m trying to find information on prep work before painting ABS plastics. I saw your question and answer about painting ABS, but my question is more about how much fine sanding I should do. What grit should I use? K. M.

A. The rules for preparing ABS and other plastic substrates for painting are similar to preparing any other substrates. The substrate must be clean, free from oily soils, release agents and particulates

To remove oily soils, plastics are cleaned using alkaline cleaners, detergent cleaners, emulsion cleaners and solvents. Release agents are best removed using recommendations from their suppliers. Certain plastic substrates must be pretreated to promote adhesion after cleaning. If necessary, plastic substrates are pretreated using abrasives, chemical etching, corona discharge, combustion spray, plasma spray and lasers. When sanding is used to abrade the substrate, the grit must be fine enough to prevent scratch or gouge marks on the surface that will show through the paint.

The applied coating must be compatible with the substrate. Compatibility of the coating with the substrate means its solvents should not attack, dissolve or otherwise destroy the substrate. Although, it is possible that the solvent attack can promote adhesion. Some plastic substrates must be primed to promote adhesion or to prevent attack by the solvents in a topcoat.