| abstract |
An improvement in a process for applying a weldable coating to a metallic substrate which process comprises applying to said substrate having a clean surface (I) a first coating containing a hexavalent chromium component and/or a phosphate component and an electroconductive pigment and thereafter curing said coating and (II) applying over said cured first coating a second coating which is a weldable coating containing a high molecular weight epoxy or phenoxy resin, a diluent and an electroconductive pigment and subsequently curing same; THE IMPROVEMENT RESIDING IN REPLACING AT LEAST 70 WEIGHT PERCENT OF SAID HIGH MOLECULAR WEIGHT EPOXY OR PHENOXY RESIN IN SAID SECOND COATING WITH A COATING COMPOSITION COMPRISING (A) a low molecular weight epoxy resin or mixtures thereof having an average of more than one vicinal epoxy group per molecule, (B) a hydroxyl-containing or thiol-containing material or mixture of such materials which is (1) a polyhydric phenolic or thiophenolic compound or (2) the product of reacting (a) a low molecular weight epoxy resin or mixtures thereof having an average of more than one vicinal epoxy groups per molecule with (b) a polyhydric phenolic or thiophenolic compound, a hydrogenated polyhydric phenolic compound or mixture of such compounds wherein the hydroxyl or thiol:epoxy equivalent ratio is from about 2:1 to about 12:1; and (C) a catalytic quantity of a catalyst for effecting the reaction between (A) and (B) and WHEREIN (A) and (B) are present in quantities such that the phenolic hydroxyl or thiol to epoxy equivalent ratio is from about 0.5:1 to about 1.1:1. |