Effects of SO2-4 on pitting corrosion behavior of X100 pipeline steel in alkaline solution

Key words:  X100 pipeline steel  alkaline solution  SO2-₄  Cl-  pitting corrosion

Abstract:

The pitting corrosion behaviors of X100 pipeline steel in simulative soil solutions with various mass fraction of SO2-₄ were investigated by electrochemical measurement. The synergistic effects of SO2-₄ and Cl-on the corrosion of X100 pipeline steel were analyzed by scanning vibrating electrode technique (SVET), and the corrosion mechanism models were established in this paper. The results show that X100 pipeline steel is characterized by a typical active dissolution, there is no obvious passive region in the simulated soil solution containing various mass fraction of SO2-₄ and Cl-. With the increase of SO2-₄ mass fraction , the polarization resistance increases significantly and the corrosion current density decreases, which indicates that X100 pipeline steel decreases the pitting corrosion tendency with the mass fraction of SO2-₄ increasing, and SO2-₄ plays a role of inhibitory corrosion anion in simulative soil solution. The corrosion mechanism is that SO2-₄ is adsorbed preferentially on the surface of the corrosion pits by competing adsorption with Cl-, the corrosion product FeS is formed simultaneously and then covers the surface of corrosion holes, thereby reduces the corrosion rate.