Insight into the Elemental Sulfur Corrosion of Carbon Steel in Chloride Bearing Media Using Electrochemical and Non-electrochemical Techniques

Abstract

This paper studies elemental sulfur-induced corrosion of carbon steel in chloride bearing media. The issue is of great importance in industries dealing with sour gas environment and its mechanism is yet not entirely understood. The aim of this study was sought using various electrochemical (such as potentiodynamic polarization, linear polarization resistance technique, electrochemical impedance spectroscopy and zero resistance ammeter technique) and non-electrochemical techniques (such as scanning electron microscopy and Raman spectroscopy). It was found that reduction of dissolved oxygen is not the main cathodic reaction in the process of the sulfur-induced corrosion. Besides, severe corrosion primarily occurs at near peripheral region of sulfur deposition, leading to formation of a ring of FeS. However, the FeS accumulation reduces the corrosion rate, over the time. In the long term, a galvanic couple is established between the near peripheral and remote regions of the sulfur deposition. Occurrence of the consequent galvanic corrosion could cause severe corrosion at the regions which are far from the sulfur deposition and are not influenced by the sulfur-based species.