Aqueous surface treatment for environment-friendly precoated metal materials, surface-treated metal materials, and environment-friendly precoated metal materials

The invention provides a chromium-free aqueous surface treatment useful as primer in producing precoated metal materials which are excellent in corrosion resistance, tight adhesion of coat (primary adhesiveness and secondary adhesiveness of coat in T-bend test), and coin scratch resistance. An aqueous surface treatment for environment-friendly precoated metal materials which contains (A) a silane coupling agent and/or a condensate of a silane coupling agent, (B) a metal oxide sol, (C) a metal compound, and (D) water-dispersible silica, wherein the metal compound (C) is at least one member selected from among compounds of V, W, Mo, Al, Sn, Nb, Hf, Y, Ho, Bi, La, Ce and Zn, and the (B)/(A) mass ratio is 1/50 to 10/1, the (C)/(A) mass ratio is 1/1000 to 4/10, and the (D)/(A) mass ratio is 1/50 to 10/1; and metal materials and chromium-free precoated metal materials, which have films made from the surface treatment.