Influence of temperature on 5 typical steel corrosion behavior under supercritical CO₂ condition

To obtain the influence rules of temperature on 5 typical steel corrosion behavior under supercritical CO₂ condition, and improve the corrosion protection effect of pipelines that are used for transporting supercritical CO₂, hightemperature autoclave was adopted to conduct the coupon corrosion comparison test. With the help of scanning electron microscope, the corrosion surface morphology of different stainless steel (DSS, 13Cr and austenitic steel) and carbon steel (X70 and P110) coupons, the surface morphology of metal matrix after removing corrosion products, the formation process of corrosion product film and the relation between coupon corrosion rate and corrosion product mass were studied under different temperatures. The results indicate that the solubility of water in supercritical CO₂ presents an approximately linear increase with the pressure, or temperature rise. In supercritical CO₂, the corrosion rate of stainless steel is one or two orders of magnitude lower than that of carbon steel. With the temperature rise, the inhibition of corrosion product film on metal corrosion exceeds the promoting effect of temperature, resulting in a reduction in uniform corrosion. However, the existence of honeycomb or striped cracks in the formation process of corrosion product film leads to serious local corrosion on the surface of the coupon. It is concluded that the influence of temperature on 5 typical steel corrosion behavior is bidirectional under supercritical CO₂ condition, in other words, the temperature rise will lower the uniform corrosion rate of pipelines, but on the other hand, it may increase the local corrosion rate.