By utilizing silica-gel as an adsorbent, ultra-high concentration ozone gas (>70 vol%) was produced from an ozone-oxygen mixture of 5 vol% ozone concentration generated by a commercial discharge cell. This highly concentrated ozone is a strong oxidant that causes a dense passivated film of 7.0 nm in thickness on the surface of stainless steel at room temperature. The concentration of metal leached from the ozone-passivated surface during dipping in pure water at below 80degreesC is one-third or one-fourth of that from the non-treated surface. This result implies that the ozone-passivated film inhibits the electrical anode and cathode reaction on the surface in oxygen-consumption-type wet corrosion. However, we could not observe the effect of ozone passivation on decreasing dissolved metal concentration in hydrogen-generation-type wet corrosion, which would occur in water at over 80degreesC.