Abstract: The pitting potential of a carbon steel and a Mn steel were determined via polarization experiments in 3% NaCl solution under removing oxygen condition and un-removing oxygen condition,and corrosion characteristics have been studied by means of electron probe micro-analyzer(EPMA).The results showed that the pitting corrosion under un-removing oxygen condition is more noble than the one under removing oxygen condition.The polarization experiments under un-removing oxygen condition could be employed to compare the susceptibility to pitting initiation for different steels more conveniently and accurately than under removing oxygen condition.