A process for coating metal surfaces in which an uncured resin coating is formed on the surface of a metal by contacting the metal surface with an autodepositing coating composition that contains acid, oxidizing agent, and water-dispersible or water-soluble organic film-forming resin, and the uncured coating is thereafter dried, produces a strongly adherent, highly corrosion-resistant autodeposited coating when the uncured coating is brought, prior to its drying, into contact with an aqueous solution that has a pH adjusted to 7 to 11 and that contains at least one selection from the following inorganic acids and salts thereof: molybdic acid, tungstic acid, polyphosphoric acid, and polysilicic acid.
An effective electrically insulating film on the surface of a metal object, such as a common type of electric motor core assembly, in which the surface includes an interior comer on which insulation is desired, can be formed by autodeposition with an adequate thickness in the interior corner without need for excessive thickness on other parts of the surface that are more readily covered by prior art methods of applying an insulating coating. If the autodeposition composition used includes as its primary film-forming component a copolymer of certain acrylic monomers, a very high volume resistivity can be achieved.
A method for formulating an aqueous dispersion of a polymer includes dissolving a polymer such as an acrylic polyol in a solvent to form a polymer solution. A surfactant is added to the polymer solution, and water is then added with mixing sufficient to dispersed the polymer in the water. The resulting aqueous dispersion can be mixed with a water dispersible polyisocyanate to produce coating materials which can be cured to form tough films and coatings.
