Can this be applied to plastic parts?
Plastics vary widely, and the condition along with the area and use also must be considered. If the plastic is rigid and weathered somewhat, you should get good adhesion for most general use. Other plastics which are newer will be somewhat of a hit and miss depending on your intended use. For these plastics, we would recommend testing a small area first by scuffing somewhat and then using an adhesion promoter such as Bull Dog adhesion promoter (available in most auto paint supply stores or online) first.