Laboratory Study of Sour Localized / Pitting Corrosion

Abstract

Abstract Carbon steel is widely used in upstream oil and gas pipelines and piping because it is cost effective and versatile. Field experience indicates that failure of carbon steel facilities in sour environments typically occurs due to highly localized / pitting, rather than general corrosion over a large surface area. Such localized / pitting attack has been attributed to the formation of anodic sites where the iron sulfide scale (cathodic) has been damaged. High pressure autoclave laboratory testing has been carried out to study the sour localized / pitting corrosion mechanism. The effects of several environmental parameters were investigated on iron sulfide scale formation, including flow rate, chloride concentration, and temperature. The effect of film forming organic corrosion inhibitor on the scale formation was also studied. It was found that severe localized / pitting attacks occurred under certain test conditions that promoted a partially protective sulfide scale. These conditions included high chloride concentration, high flow velocity, and under-treatment using corrosion inhibitor.