PURPOSE: To provide a water-soluble resin composition which has an assured necessary rust-preventive power and good driability inspite of a relatively low unsaturated fatty acid content.

CONSTITUTION: The resin composition is prepared by mixing an epoxy resin with linseed oil fatty acids as unsaturated acids, a styrene monomer and an acrylic acid monomer as essential component, and neutralizing the resulting mixture with triethylamine to make it water-soluble.