Failure analysis of anion synergy on pitting behavior of liner 316L in sour water system by electrochemical tests

Electrochemical tests were employed to study the chloride, sulfate and carbonate ions synergistically effects on pitting. The results showed that SO42- increased the pitting potential of 316L at first and then decreased, peaking at 0.2 M. In this case, the highest critical pitting temperature (12 degrees C), the breakdown potential (0.45 V-SCE), and the maximum impedance (257 k Omega cm(2)) were obtained. The existing CO32- raised the pitting potential but accelerated the general corrosion of 316L surface. The effective adsorption area based on the competitive adsorption mechanism of the anions was proposed to interpret the pitting and the passivation behaviors of 316L, and the properties of the passive film were comprehensive analyzed.

Automated summary

Electrochemical tests were conducted to investigate the synergistic effects of chloride, sulfate, and carbonate ions on pitting. The results revealed that sulfate ions initially increased the pitting potential of 316L, reaching a peak at 0.2 M concentration, before decreasing. At this concentration, the highest critical pitting temperature, breakdown potential, and maximum impedance were obtained. On the other hand, carbonate ions increased the pitting potential but accelerated the general corrosion of the 316L surface. The study proposed an effective adsorption area based on the competitive adsorption mechanism to explain the pitting and passivation behaviors of 316L, and comprehensively analyzed the properties of the passive film.