Electrochemical Noise Evaluation on Pitting of X70 Pipeline Steel in Na_2CO_3-NaHCO_3 System Containing Cl~-

The pitting corrosion behaviors of X70 pipeline steel in Na2CO3-NaHCO3 system containing Cl-were investigated by electrochemical noise technology.The results show that the metastable pitting nucleation time on X70 pipeline steel surface in the Na2CO3-NaHCO3 system containing Cl-is apparently shortened.And the repairing time of passive film becomes apparently longer after the appearance of pitting.The pitting behavior has the apparent three phases,such as unstable period,metastable pitting nucleation period and pitting period.