Coating composition for metal

A surface-treating composition for metallic surfaces which contains hexavalent chromium ions or hexavalent and trivalent chromium ions as an inorganic compound, and a mixture of acryl-series polymer emulsion set forth below and one or more lubricants dispersed by an emulsifying agent set forth below, wherein from 1 to 50% by weight (in terms of nonvolatile matters) of one or more lubricants as a lubricating component are dispersed by a first nonionic emulsifying agent which has been added for preventing coagulation of the lubricating component in the surface-treating composition wherein said emulsifying agent is added to the lubricating component and the emulsifying agent and the lubricating component are melted together, the surface-treating composition having a pH of 5 of less, wherein said acryl-series polymer emulsion is obtained by emulsion-polymerizing, by means of a second nonionic emulsifying agent which is essentially free of anionic emulsifying agent and cationic emulsifying agent and which contains a polyoxyethylene-polyoxypropylene block copolymer, monomers of 1), 2) and 3):

• 1) one or more monomer of ethylene-series, unsaturated carboxylic acid
• 2) one or more monomers selected from a), b), and c):
• a) alkoxyethylene (metha)acrylamide and its derivatives(s) expressed by the following general formula ##STR4## X is C.sub.n H.sub.2n+1 (n=0 or 1) Y is C.sub.m H.sub.2m+1 (m=0-4)
• b) acid phospho-oxyalkyl(metha)acrylate, and
• c) alkoxy-alkyl(metha)acrylate
• 3) one or more acryl-series monomers (a part of which may consist of 2) (c)) .