Abstract: The invention relates to a process for preparing compositions for coating metal substrates or work pieces in an aqueous bath, in which the substrate forms the cathode.In this process 5-35% by weight of at least one epoxy resin, 2-20% by weight of at least one ketone and/or hydrocarbon resin, 15-60% by weight of at least one cationic synthetic resin having functional groups--this compound is a 10-50% by weight dispersion or solution--, 5-30% by weight of at least one organic cross-linking agent, which is solid at ambient temperature and 0-73% by weight of pigments and/or conventional adjuvants are processed together in one or more stages in a grinding apparatus to form a homogeneous coating composition. At least one stage being a wet operation. The composition has a particle size of less than 100 .mu.m, preferably less than 15 .mu.m. The grinding bath is adjusted with water to the solids content required for application.