| abstract |
A method of preventing the yellowing of the outermost coating of a multicoat coating system is disclosed. The method comprises initially depositing onto a conductive substrate by cathodic electrodeposition a primer coating comprising at least one layer of an amine-epoxy resin adduct and a cross-linking agent, and then curing said primer to a hard, durable film. Then, depositing a second coating onto the primer layer comprising at least one layer of a pigmented film-forming basecoat. Then depositing a third outermost coating onto the second coating comprising at least one layer of a clear, film-forming topcoat, and then curing the basecoat and topcoat. The primer coating contains a cross-linking agent selected from the group consisting of aliphatic polyisocyanates containing at least six carbon atoms, the isocyanurates of aliphatic polyisocyanates containing at least six carbon atoms, aromatic polyisocyanates having a molecular weight greater than 174, and the isocyanurates of aromatic diisocyanates having a molecular weight greater than 174. The polyisocyanates or isocyanurates are blocked with a blocking agent. |