抄録
Anodic polarization curves of electro-polished Type 304 stainless steel were measured in organic acid solutions of eight types to develop a safe and environmentally friendly passivation treatment. The pitting potentials of the steel passivated in the solutions were examined in a deaerated 3.5%NaCl solution. Among the organic acid solutions, 8%DL-malic acid, 8%citric acid, 8%L-tartaric acid and 8%glucono-δ-lactone were found to be suitable as treatment solutions because of the low current densities（＜0.02 A･m－2）of the passive state and high pitting potentials（＞700 mV vs. Ag/AgCl（sat. KCl））of the passive films. Passive films formed on Type 304 stainless steel by natural immersion into 8%DL-malic acid＋0.98%H2O2, 8%citric acid＋0.98%H2O2, 8%L-tartaric acid＋0.98%H2O2 and 8%glucono-δ-lactone＋0.98%H2O2 showed high pitting potentials（＞1000 mV）in NaCl solutions of 3.5% - saturation concentration. For solutions containing H2O2, the pitting-potentialraising effects were greater on an electro-polished surface than on a buffer（#400）-polished surface.
