Painting Polystyrene Insulation

Q. We manufacture pneumatic (air operated) control equipment. We want to lag the air tanks on each compressor unit by covering them with expanded polystyrene bead insulation. We want to paint the insulation to match our units. When we tried to paint them, the polystyrene was melted by the paint solvent. We ended up covering the lagging with sheet metal, which we painted with our standard paint finish to match our units. This was very costly. I am looking for a less expensive way to lag our air tanks. Do you have any good ideas? S. J.

 

A. Painting is a problem with expanded polystyrene bead structures because they are attacked by solvents. Another concern will be surface defects and roughness which will be highly visible under a high glass topcoat. Both these problems can be solved by using a waterborne primer/surfacer.

Waterborne materials such as block fillers are available at paint and hardware stores. They will not attack the polystyrene. Not only will they fill surface defects, they will form a barrier protecting the polystyrene surface from the solvents in you standard topcoat. Even with some manual smoothing of the primer/surfacer, the overall cost will be lower than covering the lagging with sheet metal.