| 摘要 |
PURPOSE:To form a surface treated layer with superior heat and corrosion resistances at a low cost by forming an Ni or Cr layer on the surface of a steel pipe by plating, impregnating a chromic acid soln., and forming a chromium oxide layer by heating. CONSTITUTION:An Ni or Cr layer 3 is formed on the outside 2 or inside 2' of a steel or copper pipe 1 by electroplating. The pipe 1 is immersed in a chromic acid soln. having >=1.3 specific gravity to impregnate the soln. into the plated surface, and the pipe 1 is heated at 200-700 deg.C for >=20min. A heat and corrosion resistant dense thin film 4 of chromium oxide is formed on the layer 3 by repeating the immersion and heat treatment. |
