Abstract
Localized corrosion is troublesome for corrosion engineers because it is generally considered the main cause for pipeline failures in the oil and gas industry, particularly in sour systems, and it is hard to predict or detect. However, compared to general corrosion, localized corrosion is poorly understood and less studied. Hence, understanding mechanisms of localized corrosion in sour fields is critical to corrosion engineers for integrity management. In a previous study, a strong correlation between the formation of greigite and/or pyrite and the onset of localized corrosion was observed. A further comprehensive study was then required to investigate this correlation between localized corrosion and greigite and/or pyrite. Thus, novel experiments involving deposition of pyrite on the steel surface were designed and conducted for the current study to investigate if localized corrosion occurs when pyrite is deposited on mild steel in an aqueous H2S environment. It was confirmed that severe localized corrosion was observed and replicated in the presence of pyrite deposit layers. Furthermore, the impact of pyrite particle size on pit characteristics was also studied. It was found that smaller and deeper pits were observed in the presence of smaller pyrite particles. This was concluded to be due to a larger cathodic area of the small particles, compared to the same amount of larger particles.
