Primerless coating of heat-sensitive substrates

The present invention provides a method of coating substrates with at least two coatings, wherein the same polymer or resin basecoat is employed in both of the two coatings. The first coating layer also includes an adhesion promoter, thereby eliminating a primer layer. Further, the present invention provides an automated or continuous coating line or coating system including a series of coating booths, each for applying one of a series waterborne or solvent borne coatings, wherein at least the first and second booth each comprises an applicator device and feed or supply controller for feeding a desired amount of the same basecoat formulation to an applicator device, and, further wherein the first booth comprises a feed or supply controller for feeding a desired amount of an adhesion promoter to the at least one applicator device. The coating line or system enables the continuous formation of primerless multi-layer coatings, e.g. basecoat, colorcoat and clearcoat on automotive plastic substrates, from a single paint composition, mixing in color or adhesion components as needed in each booth.