PRETREATMENT OF IRON OR STEEL SURFACE HAVING IRON OXIDE COATING PRIOR TO PAINTING

摘要

PURPOSE:To improve the corrosion resistance of unpainted iron or steel, and the corrosion resistance of painted coating, by applying on the surface of iron or steel having iron oxide coating an aq. soln. which contains a water-soluble Cr cpd., or further contains water-soluble or water-dispersible resin, and a metallic oxide. CONSTITUTION:On the surface of iron or steel having iron oxide coating formed by heat treatment such as annealing is applied an aq. soln. described as follows: The aq. soln. contains water soluble Cr cpd., e.g., CrO3, CrCl3, in an amount 0.1- 50g total Cr/l, six valent Cr being not less than 10%, pref., 50-90% of the total Cr, or further contains 0.1-50g/l water-soluble or water-dispersible resin, e.g., poly(meth)acrylic acid (derivative) and 5-300g/l oxides of Si, Al, Ti, or Zr.