| 摘要 |
A chromate coating is formed on a metal, asbestos or asbestos cement surface by treating with an aqueous solution of a hexavalent chromium salt of a metal with a valency greater than 1, e.g. dichromate of Zn, Ca, Mg, Cd, Sr, Ba, Fe, Al Ni, and a polyglycol so that 40-95% of the hexavalent Cr is reduced to trivalent Cr on heating to at least 250 DEG F. The surface treated may be Fe, stainless steel, Al, Mg, Zn, galvanised Fe, or oxidised, phosphated, sulphided, chromated or oxalated surfaces. The solution may also contain a resin dispersion e.g. thermoplastic acrylates, thermosetting acrylics or butadiene styrene polymers, P.T.F.E. or polyvinyl stearate in a ratio of CrO3:resin of between 5:1 to 1.5, or 1/2 -3 parts resin to 1 part CrO3, up to 5% of chromic acid, wetting agents, pigments such as Al, Cu, brass, carbon, phthalocyanin blue TiO2 iron oxide, clay, BaSO4, and also Mn naphthenate, sucrose, hydroxyethyl cellulose and Sio2 gel. The polyethylene glycol is any polymeric form of ethyleneglycol with a molecular weight up to 9000 and the wetting agent may be cationic, non ionic or anionic. The coating is applied by spraying, electrostatic spraying, flow coating or roller coating and cured at 250 DEG -450 DEG F. The chromated surface may be painted with e.g. enamels, lacquers, chlorinated rubbers, alkyd or expoxy paints and the coating may be applied to steel strip in a continuous process, the coated strip being quenched prior to coiling.ALSO:A chromate coating is formed on a metal, asbestos or asbestos cement surface by treating with an aqueous solution of a hexavalent chromium salt of a metal with a valency greater than 1, e.g. dichromate of Zn, Ca, Mg, Cd, Sr, Ba, Fe, Al Ni, and a polyglycol so that 40-95% of the hexavalent Cr is reduced to trivalent Cr on heating to at least 250 DEG F. The surface treated may be Fe, stainless steel, Al, Mg, Zn, galvanized Fe, or oxidized, phosphated, sulphided, chromated or oxalated surfaces. The solution may also contain a resin dispersion e.g. thermoplastic acrylates, thermosetting acrylics or butadiene styrene polymers, P.T.F.E. or polyvinyl stearate in a ratio of CrO3 resin of between 5 : 1 to 1.5, or 1/2 -3 parts resin to 1 part CrO3, up to 5% of chromic acid, wetting agents, pigments such as Al, Cu, brass, carbon, phthalocyanin blue, TiO2 iron oxide, clay Ba SO4, and also Mn napithenate, sucrose, hydroxyethyl cellulose and Sio2 gel. The polyethylene glycol is any polymeric form of ethyleneglycol with a molecular weight up to 9000 and the wetting agent may be cationic, non ionic or anionic. The coating is applied by spraying, electrostatic spraying, flow coating or roller coating and cured at 250 DEG -450 DEG F. The chromated surface may be painted with e.g. enamels, lacquers, chlorinated rubbers, alkyd or epoxy paints and the coating may be applied to steel strip in a continuous process, the coated strip being quenched prior to coiling. |
