Abstract: A colloidal particle dispersion is disclosed, comprising mainly (1) a fumed silica or fumed aluminum silicate, (2) a colloidizing agent (aid) which is at least one compound selected from the group consisting of a phosphoric acid compound, a molybdic acid compound, a boric acid compound, and a silicic acid compound, and (3) water, and a method for preparing the same is disclosed. Further, a water-based coating composition is disclosed, which comprises a water-based coating composition and incorporated therein a colloidal particle dispersion comprising mainly (1) fumed silica or fumed aluminum silicate, (2) a colloidizing agent (aid) which is at least one compound selected from the group consisting of a phosphoric acid compound, a molybdic acid compound, a boric acid compound, and a silicic acid compound, and (3) water, and a method for preparing the same is disclosed. Furthermore, the coating method with which the above water-based coating composition on a metal substrate is disclosed.

Abstract: An aqueous coating composition for formation of a coating film having high corrosion-resistance on a metal substrate which comprises (a) a film-forming polymeric material having at least one hydroxyl group and/or at least one carboxyl group, (b) a zwitter-ion compound and (c) an aminoplast resin and/or an epoxy resin with or without (d) a surface active agent having a hydrophilic functional group and at least one hydroxyl group and/or at least one carboxyl group.