Aqueous resinous binders comprising graft copolymers, water-dilutable urethane polyols, epoxy-phosphorus acid reaction products, and an aqueous dispersion comprising the reaction product of trimellitic anhydride and a polyol, wherein the molar ratio of trimellitic anhydride to the polyol in the reaction product ranges from 1:2 to 1:4, and wherein the reaction product is further reacted with an anhydride to form another reaction product are disclosed. The binders are useful in primer formulations for automotive applications.