Q. My company manufactures small plastic items, many of them made using parts molded in various colors. One line of products is fabricated from black PVC irrigation pipe. I would like to be able to offer these products in colors other than black. The coating must be abrasion-resistant enough to withstand metal and plastic objects sliding across its surface without scratching. M.W.
A. I am sure you are aware that many paint solvents will attack PVC pipe and cause anything from surface etching to softening and distortion. However, there are a few solvent-thinned paints that can be used on PVC. I have used some of these on plastic structures for my model railroad without damage.
It is best to protect the PVC from solvent attack using a waterborne coating. Then you will be able to apply an abrasion-resistant coating. To coat the PVC parts without destroying them, you have two choices:
1) Apply a two-coat finish consisting of a waterborne primer topcoated with a compatible epoxy or polyurethane enamel in the color of your choice.
2) Apply a one-coat finish consisting of a water-reducible epoxy or water-reducible polyurethane enamel.
These are industrial coatings available from paint companies.
There is a caveat, however. Since some waterborne paints contain co-solvents that may attack the PVC, test them before you buy them. I have seen a line of spray paint advertised as specifically formulated to paint plastics that can be purchased from Big Box stores, but I have not tried it. These spray paints may coat PVC without damage, but I don’t know anything about their abrasion resistance. It may be worth trying on your PVC products. Otherwise, I suggest you contact your local paint salesman or the industrial sales department of a paint company for their recommendations.