For their superior CO2 corrosion resistance and relatively low cost, the new generation of low Cr (3 to 5%) bearing steels seem to be a good choice to meet the demand of preventing wet CO2 corrosion of sub-sea wet gas pipelines. The data of extensive laboratory assessment and field experience have confirmed that low Cr bearing steels have an improved corrosion performance when immersed in CO2 containing solutions, while the resistance to wet CO2 corrosion has not been clarified. In this paper the effect of temperature on wet CO2 corrosion of 3%Cr pipeline steel was investigated. Wet CO2 corrosion environment in sub-sea wet gas pipelines was simulated in a high temperature and high pressure autoclave. A series of experiments were carried out at wet gas temperature of 30~90?, while the cooling temperature was kept relatively low to provoke water condensation on the surface of coupons, ranging from 10? to 30?. The corrosion rate was determined by weight loss measurement. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrum (EDS) were employed to analyze the corrosion scales.
The carbon dioxide (CO2) corrosion of carbon steels has been a severe problem in the oil and gas industry for many years, causing huge damages every year.1, 2 Because of their cost effective characteristics, carbon steels are widely used as construction materials for pipelines.3 However, due to their poor CO2 corrosion resistance, carbon steels are very susceptible to top of line corrosion, causing severe damages to pipelines for wet gas transportation. Previous studies have demonstrated that 3%Cr steel used as tubing can improve the CO2 corrosion resistance by a factor of 3-10 while maintain the cost less than 1.5 times that of conventional grades of carbon steels.