To develop effects of surface polishing conditions on pitting resistance after passivation treatments, pitting potentials of Type 304 stainless steels finished using different polishing techniques and passivated with HNO
3 solutions of different types were measured in deaerated 3.5%NaCl. Steel finished with electropolishing and then passivated in 30%HNO
3 showed high pitting potential of 1010 mV (vs. Ag/AgCl (sat. KCl)), which is in a trans-passive potential region. Increased pitting potential of 1053 mV was obtained when 0.1 kmol・m
-3Na
2MoO
4-containing 30%HNO
3 was used for passivation. Steel finished with mechanical polishing never showed such high pitting potential. No decrease in pitting potential was observed on steel finished with electropolishing and 30%HNO
3 or 0.1 kmol・m
-3Na
2MoO
4-containing 30%HNO
3 passivation after accelerated corrosion tests such as long term immersion in aerated 3.5%NaCl, salt spraying with 5%NaCl or steaming at 121 °C. To achieve high pitting resistance, combined surface treatment of electropolishing and 30%HNO
3 or 0.1 kmol・m
-3Na
2MoO
4-containing 30%HNO
3 passivation is recommended for Type 304 stainless steels.
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