GB1316890A - Treatment of steel - Google Patents

Abstract

1316890 Enamelling HOESCH AG 19 April 1971 [9 April 1970] 23394/71 Heading C1M [Also in Division C7] To prepare steel for enamelling, it is first pickled either (a) chemically in HNO 3 or (b) anodically (e.g. in a bath containing HNO 3 and/or H 2 SO 4 ) and then coated electrolytically (see Division C7) with Fe and one or two of Ni, Co and Mn, the metals being deposited either as a co-deposite or as separate layers. Thereafter, the steel may be subjected to at least one of the following: (i) chemical treatment in HNO 3 or anodic treatment in H 2 SO 4 , (ii) electrolytic Zn plating with chemical removal of the Zn prior to the enamelling and (iii) coating with a stoving varnish or lacquer. The varnish may contain white or coloured pigmented enamel frit particles and may be applied as a liquid mixture in organic solvents containing, on the basis of the solids content, a copolymer of (a) 1% to 98% by weight of an acrylate polymer, (b) 1% to 98% by weight of a film-forming binder selected from (1) coumarone resins, (2) ketone resins and (3) coumarone or ketone resins combined with hydrogenated abietyl alcohol and (c) 1% to 40% by weight of benzene dicarboxylic acid ester. The plated and varnished steel may be heated to a temperature such as to melt the frit particles but not to depolymerize the varnish; thereafter the steel may be deformed to a desired shape; and later the product may be heated to a higher temperature so as to completely depolymerize and evaporate the varnish and fuse the enamel frits into a uniform coating. Initially, the steel may be in the form strip, sheet or a part and may have a carbon content of 0À04-0À10% or of 0À006%.