PURPOSE: To provide a coating agent for metals, having excellent drying characteristics, hardness, golss, and adhesivity, comprising an aqueous emulsion containing a polymer or copolymer composed mainly of nitrocellulose and a (meth)acrylic acid alcohol ester.

CONSTITUTION: A coating agent comprising an aqueous emulsion of polymers wherein each particle dispersed in water is composed of a homogeneous mixture of 5W45wt% of nitrocellulose and 55W95wt% of a homo- or copolymer composed mainly of a (meth)acrylic acid ester of a 1W10C alcohol. When the content of the nitrocellulose is less than 5wt%, the drying characteristics, the hardness, and the gloss of the coating film are remarkably decreased, and when it exceeds 45wt%, the weatherability becomes poor. To improve the stability of the polymer or the copolymer, 1W5 parts by weight of (meth)acrylic acid may be incorporated to 100 parts of the 1W10C alcohol (meth)acrylate.