Passivation Treatment of Electro-polished Type 304 Stainless Steel with H₂O₂ Solutions

Abstract

To develop a safe and environmentally friendly passivation treatment, the pitting resistance of Type 304 stainless steels, which were finished with different polishing methods and then passivated in H 2 O 2 solutions under various conditions, were examined by measuring their pitting potentials in deaerated 3.5 %NaCl. Results show that pitting potentials were strongly dependent on the surface polishing conditions. A remarkable increase in pitting potential was attained on an electro-polished surface. The highest resistance to pitting was obtained on a surface treated in 3.5 %H 2 O 2 at 25 ℃ for 2 h. The steels treated under this condition showed extremely high pitting potential of 1075 mV （vs. Ag/AgCl （sat. KCl） ） in 3.5 %NaCl, but they showed no change in pitting potential after immersion in aerated 3.5 %NaCl for 100 d. Change in anodic polarization curves of electro-polished and passivation-treated Type 304 stainless steel in deaerated 3.5 %NaCl with immersion time in aerated 3.5 %NaCl. The electro-polished steel was passivated in 3.5 %H O for 2h and then immersed in aerated 3.5 %NaCl for 1-100d before the measurement of anodic polarization curves in deaerated 3.5 %NaCl.Contents of