Unlike wood surfaces, plastic is slick and nonporous, making it ill-suited for paint adhesion. Without proper preparation, plastic will shed its painted finish relatively soon after application. Like vinyl and fiberglass, plastic must be conditioned to accept paint through abrasion. After the proper preparation steps are performed, most any type of paint will stick to a plastic surface.
Dust particles will inhibit paint adhesion. Plastic surfaces should be washed with dish soap before the application process begins. Soap can also interfere with adhesion. It's important to rinse the plastic thoroughly, or the primer and paint may peel.
Slick, nonporous plastic surfaces lack a tooth for the primer and paint to adhere. The plastic should be scoured with sandpaper prior to application of primer. A 220 grit sandpaper is appropriate for plastic. Sandpapers with lower grits can scar plastic surfaces with scratches.
Abraded plastic surfaces require a primer base coat. Acrylic latex primers are appropriate for most malleable plastic surfaces. Oil-based primers should only be used if you plan to use oil-based paint afterward.
Acrylic latex paints are appropriate for malleable plastic surfaces, because they provide elasticity and won't crack or chip as the plastic bends. Oil-based enamel paints can be used on stiff plastics, but should never be used on plastics that bend. Oil-based enamels offer more durability than latex paints, but are not as flexible. Those who want a durable finish for their stiff plastics, but want to avoid oil-based paints, should choose a water-based appliance epoxy.
Water-based acrylic primers and paints should not be used with oil-based primers and paints, because this will cause the finish to chip and peel. Plastic surfaces should not be painted unless they have been abraded and primed first. Improper preparation will cause plastic to shed any type of paint.