Chrome free resin composition having good alkaline resistance and forming properties, method for surface treating steel sheet using the same and surface-treated steel sheet

摘要

Resin mixture without chromium content with good resistance against bases and having good treatability for surface treatment of steel plate containing mixture of urethane resin of soft urethane resin and hard urethane resin; organic oxide on the basis of Ti or Zr; at least one compound selected from group consisting of aluminium phosphate, aluminium dihydrogenphosphate, zinc phosphate and hydrated manganese phosphate; and solvent; wherein the mixture of urethane resin is present in amount from 10 to 90 % by weight and contains 5 to 95 % by weight of soft urethane resin and 5 to 95 % by weight of hard urethane resin, the organic oxide on the basis of Ti or Zr ispresent in amount 5 to 20 % by weight and at least one compound selected from the group of aluminium phosphate, aluminium dihydrogenphosphate, zinc phosphate and hydrated manganese phosphate is present in amount from 0.1 to 10.0 % by weight in relation to the whole solid content of the resin preparation. Method for surface treatment of the steel plate with the resin mixture and surface treated steel plate with use of the resin mixture are also provided.