A coating composition for metallic surfaces contains: (1) Cr6+, or Cr6+ and Cr3+, (2) 1-50% of lubricant(s) dispersed by a nonionic emulsifying agent, (3) acryl-series polymer emulsion, which is obtained by emulsion-polymerizing, by means of a nonionic emulsifying agent which is essentially free of anionic and cationic emulsifying agent and which contains a polyoxyethylene-polyoxypropylene block polymer, monomers of A), B), and C): A) a monomer of ethylene-series, unsaturated carboxylic acid B) one or more monomers selected from a), b), and c): a) alkoxyethylene(metha)acrylamide and its derivative(s) expressed by the following general formula(m=0-4) b) acid phospho-oxyalkyl(metha)acrylate, and c) alkoxy-alkyl(metha)acrylate C) one or more acryl-series monomers (a part of which may consist of 2)(c)).