Influence of Chloride and Hydrogen on Electrochemical Corrosion Behavior of a New Kind of Ultrahigh Strength Steel Cr12Ni4Mo2Co14 in Acid Environment

The electrochemical corrosion behavior of a new kind of ultrahigh strength steel Cr12Ni4Mo2Co14 in acid environment was studied by electrochemical methods of polarization curves testing, electrochemical impedance spectroscopy (EIS) testing and Mott-Schottky testing. Both chloride ion and hydrogen can affect the anode passivation zone of Cr12Ni4Mo2Co14 steel. With the increase of concentrations of chloride ion and hydrogen, the pitting potential moved negatively and the passivation zone was narrowed. The Schottky pairs were formed by chloride ions occupying vacancies of oxygen. Vacancies of metal ions gathered, which broke the passive film. Donor and acceptor densities of hydrogen-charged Cr12Ni4Mo2Co14 steel increased in comparison with those of non hydrogen-charged Cr12Ni4Mo2Co14 steel, which increased the concentration of positive ion vacancy. Then the passive film can be broken by the gather of positive ion vacancies at local area.