TREATING FLUID FOR SURFACE TREATMENT OF METAL AND METHOD FOR SURFACE TREATMENT

摘要

An aqueous fluid for surface treatment for use in surface-treating one metal material selected from iron based materials, zinc based materials, aluminum based materials and magnesium based materials, or surface-treating, at the same time, two or more of the above metal materials, characterized in that it comprises one or more compounds selected from zirconium compounds and titanium compounds in an mount of 5 to 5000 ppm in terms of the metal and 0.1 to 100 ppm of a free fluoride ion and has a pH of 2 to 6; and a method for the surface treatment of the metal material, which comprises contacting the metal material with the aqueous fluid or subjecting the metal material to an electrolytic treatment in the aqueous fluid, to form a coating film. The fluid may further comprise a calcium compound, a magnesium compound or a strontium compound, a phosphate residue, an oxygen acid and/or a salt thereof , a polymer and a surfactant. The aqueous fluid is free of a component harmful to the environment and the method allows the precipitation, on the surface of a metal, of a surface treatment coating film being excellent in the corrosion resistance after coating, without generating a sludge resulting in a waste.