Study on the Influence of Sodium Chloride Concentration on the Electrochemical Corrosion Behavior of X80 Pipeline Steel Base Material and Weld Zone

Abstract

With the continuous development of China's offshore oil and gas resources, the corrosion of pipeline welded joints has become one of the main factors leading to the failure and safety of marine operating pipelines. In order to provide more accurate theoretical basis and practical guidance for corrosion protection and material selection of marine pipelines, the electrochemical corrosion behaviors of the base material and weld zone of X80 pipeline steel welded joints were studied in different NaCl solution concentrations(1.5%, 3.5%, 5.5%, mass fraction) via dynamic potential polarization technology and electrochemical impedance spectroscopy testing method. Results showed that in the solutions with different NaCl concentrations, the polarization curves of the base material and weld zone exhibited obvious anodic dissolution characteristics without passivation phenomenon. With the increase of NaCl concentration, the open circuit potential and self-corrosion potential of the two regions shifted negatively, the polarization resistance first decreased and then increased, and the self-corrosion current density first increased and then decreased. Furthermore, the thermodynamic stability and corrosion resistance of the base material zone were always superior to those of the weld zone.

Keywords

• weldzone; x80 pipeline steel; electrochemical corrosion; nacl concentration