Synergistic Effect of Cl^- and SO₄^2- on the Corrosion Behavior of 316L Stainless Steel

Abstract

In order to reduce the harm caused by corrosion to the normal operation of offshore oil and gas pipelines, the effects of the synergistic effect of Cl- and SO42- on the corrosion behavior of 316L stainless steel in the simulated South China Sea marine environment were investigated through the AC impedance technique and the cyclic polarization technique in electrochemical tests, and the corrosion morphology of 316L stainless steel surface was characterized by scanning electron microscopy(SEM). Results showed that when the SO42- content was constant, an increase in Cl- content could reduce the capacitive arc radius, polarization resistance Rp and pitting potential Eb. As the Cl- content increased from 0 to 50 g/L, significant corrosion was observed on the surface of 316L stainless steel. When the Cl- content was constant, an increase in SO42- content reduced the capacitive arc radius, Rp and Eb values. At the same time, the diameter of the corrosion pit on the surface of the specimen expanded, and the depth gradually deepened.

Keywords

• 316l stainless steel; marine environment; cl^-; so₄^2-; synergistic effect; cyclic polarization