Paint Undercoat Primer
The Undercoat is a term used broadly to describe the coatings which can provide a base for the final coat It includes primers, primer colour coats.surfacers, fillers, stoppers and sealers.
A prirner is an undercoat designed to ensure that the paint system adheres well to the substrate, initially and in service. It is generally used over bare metal, although it can also be used over old finishes. As its main function is to establish a secure base for the paint system as a whole, a primer is most effective if applied in a relatively thin film. Primers are not formulated to fill scratches or to be flatted. For a very light rubbing down that should be carried out.