Abstract: Thermosetting aqueous anionic electrocoating composition are disclosed which comprise a carboxyl-functional anionic polymer dispersed in water with the aid of water miscible organic solvent and a volatile base, and from about 1% to about 5%, based on the weight of the polymer content of the composition, of an oxirane-free epoxy phosphate, this epoxy phosphate being produced by slowly and incrementally adding a resinous polyepoxide to a solvent solution containing from 0.05 to 0.9 mole of orthophosphoric acid per oxirane equivalent in the polyepoxide together with sufficient water to hydrolyze all of the oxirane functionality which is not consumed by the orthophosphoric acid. These epoxy phosphates improve the corrosion resistance of electrodeposited cured coatings without objectionably wrinkling their surface.

Abstract: Aqueous thermosetting cationic electrocoating compositions are disclosed in which an amine-functional cationic polymer is dispersed in water with the aid of an acid, a curing agent being added if the polymer is not self-curing, and there is added from 1% to 30% of the polymer content of the composition of an oxirane-free epoxy phosphate. This epoxy phosphate is produced by slowly and incrementally adding a resinous polyepoxide to a solvent solution containing from 0.05 to 0.9 mole of orthophosphoric acid per oxirane equivalent in said polyepoxide together with sufficient water to hydrolyze all of the oxirane functionality which is not consumed by the orthophosphoric acid. When the epoxy phosphate is made in the manner set forth, the salt spray resistance of electrodeposited cured films is improved.