US 6,143,365 A · Autodeposited coating with improved thermal stability and composition and process therefor

Abstract

The susceptibility to heat degradation of an autodeposited coating in which the principal organic constituents are copolymers of vinylidene chloride in which vinylidene chloride residues constitute at least half the weight of the total binder phase in the autodeposited coating is improved if the wet autodeposited coatings are rinsed, before being later dried and cured, with a water-based liquid rinse that comprises dissolved phosphate ions in a concentration that corresponds stoichiometrically to at least 0.5 g/l of tripolyphosphate ions. The water-based liquid rinse preferably has a strongly alkaline pH and also comprises dissolved organic molecules that are effective chelating agents for dissolved iron cations by reason of having in each molecule at least two carboxyl, carboxylate, and/or other hydroxy moieties.

Claims12

Dependent claims

A process for forming an autodeposited coating with improved thermal stability on an active metal substrate, said process comprising operations of:

(I) contacting the active metal substrate with an autodepositing composition that comprises as its predominant coating resin a copolymer of vinylidene chloride, residues of vinylidene chloride constituting at least 50% by weight of the total weight of said copolymer, so as to form on the active metal substrate a wet adherent autodeposited coating;
(II) contacting the wet adherent autodeposited coating formed in operation (I) with a water-based liquid rinse comprising a concentration of tripolyphosphate ions that is at least about 0.5 g/l, so as to form a phosphate-rinsed wet adherent autodeposited coating;
and
(III) heating the phosphate-rinsed wet adherent autodeposited coating so as to convert it to a cured dry autodeposited coating.

1 more element

A process for forming an autodeposited coating with improved thermal stability on an active metal substrate, said process comprising operations of:

(I) contacting the active metal substrate with an autodepositing composition that has been made by mixing with water a stable dispersion in water of copolymer molecules of vinylidene chloride, residues of vinylidene chloride constituting at least about 50% by weight of the total weight of said copolymer molecules and said copolymer molecules together constituting at least about 50% by weight of all organic molecules in said autodepositing composition;
(II) contacting the wet adherent autodeposited coating formed in operation (I) with a water-based liquid rinse that has been made by mixing with a first mass of water at least a second mass of a water soluble salt of tripolyphosphoric acid, said second mass containing a sufficient quantity of tripolyphosphate ions to correspond to a concentration of tripolyphosphate ions that is at least about 0.5 g/l of the total water-based liquid rinse, so as to form a phosphate-rinsed wet adherent autodeposited coating;
and
(III) heating the phosphate-rinsed wet adherent autodeposited coating so as to convert it to a cured dry autodeposited coating.

1 more element

Dependencies are inferred from the claim text.

Autodeposited coating with improved thermal stability and composition and process therefor

Life of this patent

Autodeposited coating with improved thermal stability and composition and process therefor

Life of this patent

Abstract

Claims12