Patent ID: 6033492
Filing Date: 2000-03-07
Classification: B05D

Abstract:
A process for coating a metal surface, said process comprising steps of:(I) bringing said metal surface into contact with an autodepositing water-based coating composition comprising water and (A) a coat-forming resin dispersed in the composition, (B) an acid, and (C) an oxidizing agent, and, optionally, (D) metal ions and maintaining contact between said coating composition and said metal surface for a sufficient time that a wet autodeposited film forms on said metal surface;(II) discontinuing contact between said wet autodeposited film and any of said coating composition that is not physically incorporated into said wet auto-deposited film;(III) contacting the wet autodeposited film formed in steps (I) and (II), while it is still wet, with an aqueous modifying rinse composition having a pH value from 6 to 11 and comprising a total of from 0.2 to 10.0 g/L of polymer molecules selected from the group consisting of (i) homopolymer molecules and copolymer molecules of carboxylic acid monomers having an ethylenic double bond and (ii) salts of the polymer molecules as recited in part (i), so as to produce a modified wet autodeposited film;(IV) discontinuing contact between said modifed wet autodeposited film and any of said aqueous modifying rinse composition that is not physically incorporated into said modified wet autodeposited film; and(V) hot drying the modifed wet autodeposited film formed in steps (III) and (IV), so as to convert the modified wet autodeposited film into an adherent dry autodeposited coating on the metal surface.