Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (6): 1093-1104.doi: 10.3866/PKU.WHXB201504032

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

Effects of Sulfate Ions on Anodic Dissolution and Passivity of Iron in Slightly Alkaline Solutions

CHEN Jun-Jie, XIAO Qian, Lü Zhan-Peng, AHSAN Ejaz, XIA Xiao-Feng, LIU Ting-Guang   

  1. 1 Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, P. R. China;
    2 State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072, P. R. China
  • Received:2015-02-02 Revised:2015-04-03 Published:2015-06-05
  • Contact: Lü Zhan-Peng E-mail:zplu@shu.edu.cn
  • Supported by:

    The project was supported by the International Cooperative Project Sponsored by Science and Technology Commission of Shanghai Municipality, China (13520721200), Specialized Research Fund for the Doctoral Program of Higher Education, China (20123108110021), and Shanghai Pujiang Project, China (12PJ1403600).

Abstract:

The effects of sulfate concentration on the open circuit state and anodic polarization behavior of iron in dilute bicarbonate solutions were investigated using immersion tests, electrochemical measurements, and surface analysis techniques. In the absence of sulfate or in the presence of a low concentration of sulfate in dilute bicarbonate solutions, iron was in a passive state, with a corrosion potential of (-0.225±0.005) V. A high electrochemical impedance and low corrosion rate were obtained. No obvious active-passive transition was observed in the anodic polarization curves. In the presence of a high concentration of sulfate in dilute bicarbonate solutions, iron was in an active dissolution state, with a corrosion potential of (-0.790±0.010) V. A low electrochemical impedance, high corrosion rate, and typical active-passive transition in anodic polarization curves were observed and related to the sulfate concentration. In the presence of a high concentration of sulfate, the anodic polarization curves showed current peaks as a result of iron activation by sulfate ions. Sulfate ions of sufficiently high concentration in solutions degraded previously formed oxide layers on iron or transformed oxide layers in bicarbonate solutions. The transition of the open circuit state from passivity to active dissolution occurs at a lower sulfate concentration in a deaerated solution than in an aerated solution.

Key words: Iron, Electrochemical behavior, Corrosion weightloss, Passivity, Anodic dissolution, X-ray photoelectron spectroscopy, Potential-pH diagram

MSC2000: 

  • O646