Abstract:
An acidic aqueous coating composition containing an organic coating-forming material forms on a metallic surface immersed therein a coating, the weight or thickness of which is related to the time the surface is immersed in the composition. The coating composition, which tends to become unstable as a result of the build up of metal ions in the composition, is stabilized by removing the metal ions with an ion exchange material. Also, in maintaining stability, anionic and/or nonionic surfactants or dispersing agents, which are present in the composition to disperse the organic-coating forming material, are added to the composition in an amount in excess of that which is added to replenish the organic coating-forming material as it is consumed during use. Also, coating compositions treated with the ion exchange material tend to produce coatings which have a textured or grainy appearance. The texturing of coatings can be avoided by contacting the coating composition with the ion exchange material in the presence of a cationic surfactant or an amphoteric surfactant which has cationic properties in the acidic aqueous coating composition, or other material which maintains the relatively small particles of the organic coating-forming material in the composition.
Abstract:
An autodepositing coating process wherein a coating bath containing an acidic aqueous coating composition comprising as essential ingredients: (1) an acid; (2) an oxidizing agent; and (3) an aqueous dispersion of coating forming resin particles and surfactant, which surfactant is subject to being slowly altered by the acidic oxidizing environment in the metal coating bath resulting in the buildup of reaction products in the bath, which bath is maintained in continuous coating forming operability by replenishing in a manner which prevents the deterioration of the coating quality of the bath. The coating composition and replenishing composition may also contain as an optional ingredient an aqueous dispersion of pigment and surfactant and may also contain non-essential ingredients, which non-essential ingredients may increase in concentration as the bath is operated until a deleterious effect is asserted on the coating formation. The coating quality of the replenished bath is maintained by the addition of an aqueous surfactant composition and by operating the replenished bath at an elevated redox potential or by removal of the altered surfactant.
Abstract:
An autodepositing coating process wherein a coating bath containing an acidic aqueous coating composition comprising as essential ingredients: (1) an acid; (2) an oxidizing agent; and (3) an aqueous dispersion of coating forming resin particles and surfactant, which surfactant is subject to being slowly altered by the acidic oxidizing environment in the metal coating bath resulting in the buildup of reaction products in the bath, which bath is maintained in continuous coating forming operability by replenishing in a manner which prevents the deterioration of the coating quality of the bath. The coating composition and replenishing composition may also contain as an optional ingredient an aqueous dispersion of pigment and surfactant and may also contain non-essential ingredients, which non-essential ingredients may increase in concentration as the bath is operated until a deleterious effect is asserted on the coating formation. The coating quality of the replenished bath is maintained by the addition of an aqueous surfactant composition and by operating the replenished bath at an elevated redox potential or by removal of the altered surfactant.