Panels received by bodyshops fall into two categories:

a) Transit type primers which are usually cheap dip primers applied solely to protect the panel during transit and storage and must be fully removed prior to painting. These are easily recognised by the large amounts of runs on the paint from the dipping process. They are generally soft and clog the flatting paper or machine sanding devices and they are easily removed with gun wash.

b) OE type primers which are generally electrocoat applied over phosphate pretreated metal. These are often labeled, but can be recognised by the fact that there are no runs (well not many) in the primer. The surface often appears semi-glossy and the primer machine flats crisply. Removal of this coating is not necessary and is liable to lead to a poorer durability if removed.

Surface preparation requires removal of any surface contaminants with solvent wipe and the surface keyed to increase mechanical and chemical adhesion.