Resin coated metal substrates

A process of coating a metal substrate in the form of a pipe having at least 100 mm internal diameter or a container which comprises (1) providing an epoxy resin coating composition formed from a homogenized solid mixture of (A) a solid epoxy resin based on epichlorohydrin and a component selected from the group consisting of (a) 4,4'-diphenylolpropane, (b) 4,4'-diphenylolmethane and (c) a combination of (a) and (b), (B) from 1 to 12% by weight based on the epoxy resin of at least one hardener for said epoxy resin selected from the group consisting of (a) compounds of formula ##STR7## wherein R is hydrogen or an alkyl group of 1 to 6 carbon atoms or an aromatic hydrocarbon residue with 6 to 10 carbon atoms, (b) compounds of formula ##STR8## wherein R is hydrogen or an alkyl group having 1 to 6 carbon atoms or an aromatic hydrocarbon residue with 6 to 10 carbon atoms and (c) an adduct of any one of the hardener compounds (a) and (b) to an epoxy resin with an epoxy equivalent weight of from 50 to 2000, (C) a flow imparting amount of a flow agent of 0.1 up to 5% by weight based on the epoxy resin and D) a thixotropic agent in an amount of 1 to 5% by weight of the total composition and (2) heating said substrate to a temperature above the melting temperature of the epoxy resin component of said mixture and sufficient to cure the epoxy resin thereof, and powder-coating the said epoxy resin mixture onto the hot surface of the substrate to provide a substantially uniform coating thereon at least 100 microns thick by immediate hardening without any further processing step by means of the heat capacity of the hot substrate.