ELEMENTAL SULFUR CORROSION OF MILD STEEL AT HIGH CONCENTRATIONS OF SODIUM CHLORIDE

摘要

Elemental sulfur deposition commonly occurs in sour gas production fields, especially in high H_2S concentration level reservoirs. In aqueous conditions, contact of solid sulfur with mild steel can initiate catastrophic corrosion problems. According to the previous research, in the presence of high concentration of salt, the corrosion process may be dramatically accelerated. The objective of this project is to study the effect of high sodium chloride concentration on elemental sulfur corrosion of mild steel. Sulfur-mild steel corrosion at both salt free and 10 wt.% sodium chloride conditions was investigated. Severe corrosion attack to the steel was found in both of the studied conditions. Iron sulfide films/scales readily formed on the surface of the steel. These were analyzed by infinite focus microscopy (IFM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Corrosion products were mostly generated in the periphery area of sulfur pellet at the high salt concentration conditions, which is different from the observation at salt free conditions. It was also found that an increase of salt concentration significantly increases the uniform corrosion rate, as well as the localized corrosion rate.