Patent GB-884675-A (GB)
Title: Improvements in and relating to the coating of metals
IPC: C09D5/08
Filed: 1958-06-19
Abstract: A composition for coating metals comprises an aqueous dispersion of a non-waxy hydrophobic resin (defined as including inter alta bodied linseed and tung oils), chromic acid or a soluble dichromate of a metal having a valency greater than unity, and a soluble reducing agent, compatible with the dispersion for at least one hour at 80 DEG F. the ratio of resin to chromic acid (or chromic acid equivalent of the dichromate) being from 1:5 to 5:1, and the reducing agent being present in sufficient concentration to reduce from 40% to 95% of the chromium compound when the coating is dried at 212 DEG  F.  Other suitable resins are acrylate polymers, alkyd resins, butadienestyrene copolymers, melamine-formaldehyde resins, polystyrene and polyvinyl chloride.  A further coating of a paint, nitrocellulose lacquer or resin may be applied, the resin therein being preferably of the same kind as that in the chromium-containing coating; when both layers contain an alkyd resin the final heating step which may be at up to 450 DEG  F. may be deferred until after application of the top coat, the two resinous layers then being cured simultaneously.  The dichromate may be zinc dichromate or cupric dichromate; the preferred reducing agent is sucrose, but ethanolamine and the reagents listed in U.S.A. Specification 2,777,785, may also be used, also polyvinyl alcohol and metallic maleates and lactates.  Emulsifying agents may be included in the composition.  The metal coated may be in the form of continuous strip, sheets, or preformed articles such as motor car bodies or television cabinets; it may be steel or other specified metals. U.S.A. Specifications 2,634,245, 2,635,086, 2,655,480, 2,683,698, 2,689,242, 2,768,103, 2,768,104 and 2,773,623 also are referred to.ALSO:A composition for coating metals comprises an aqueous dispersion of a non-waxy hydrophobic resin (defined as including inter alia bodied linseed and tung oils), chromic acid or a soluble dichromate of a metal having a valency greater than unity, and a soluble reducing agent, compatible with the dispersion for at least one hour at 80 DEG  F., the ratio of resin to chromic acid (or chromic acid equivalent of the dichromate) being from 1:5 to 5:1, and the reducing agent being present in sufficient concentration to reduce from 40% to 95% of the chromium compound when the coating is dried at 212 DEG  F.  Other suitable resins are acrylate polymers, alkyd resins, butadiene-styrene copolymers, melamine-formaldehyde resins, polystyrene and polyvinyl chloride.  A further coating of a paint, nitrocellulose lacquer or resin may be applied, the resin therein being preferably of the same kind as that in the chromium-containing coating; when both layers contain an alkyd resin the final heating step which may be at up to 450 DEG  F. may be deferred until after application of the top coat, the two resinous layers then being cured simultaneously. The dichromate may be zinc dichromate or cupric dichromate; the preferred reducing agent is sucrose, but ethanolamine and the reagents listed in U.S.A. Specification 2,777,785 may also be used, also polyvinyl alcohol and metallic maleates and lactates. Emulsifying agents may be included in the composition.  U.S.A. Specifications 2,634,245, 2,635,086, 2,655,400, 2,683,698, 2,689,242, 2,768,103, 2,768,104 and 2,773,623 also are referred to.ALSO:A composition for coating metals comprises an aqueous dispersion of a non-waxy hydrophobic resin (defined as including inter alia bodied linseed and tung oils), chromic acid or a soluble dichromate of a metal having a valency greater than unity, and a soluble reducing agent, compatible with the dispersion for at least one hour at 80 DEG F., the ratio of resin to chromic acid (or chromic acid equivalent of the dichromate) being from 1 : 5 to 5 : 1, and the reducing agent being present in sufficient concentration to reduce from 40% to 95% of the chromium compound when the coating is dried at 212 DEG F.  Other suitable resins are acrylate polymers, alkyd resins, butadiene-styrene copolymers, melamine-formaldehyde resins, polystyrene and polyvinyl chloride. The dichromate may be zinc dichromate or cupric dichromate; the preferred reducing agent is sucrose, but ethanolamine and the reagents listed in U.S.A. Specification 2,777,785 may also be used, also polyvinyl alcohol and metallic maleates and lactates. Emulsifying agents may be included in the composition.  The metal coated may be in the form of continuous strip, sheets, or preformed articles such as motor car bodies or television cabinets.  U.S.A. Specifications 2,634,245, 2,635,086, 2,655,480, 2,683,698, 2,689,242, 2,768,103, 2,768,104 and 2,773,623 also are referred to.