Effect of organic acid on corrosion behavior of 13Cr stainless steel in CO_2 contained solution

摘要

Corrosion of oil and gas production system is affected by many factors, such as temperature, pressure, CO_2, H_2S, chloride ion, and organic acids. In this study, effects of formic, acetic and propionic acids on corrosion behavior of 13%Cr stainless steel have been mainly investigated because previous data and information of the effects are not enough to understand corrosion mechanism of 13%Cr stainless steel. The study has been conducted by experiments using electrochemical method in the simulated oil and gas production service. The experiment results showed that the organic acids affect polarization curves of both cathodic and anodic reaction. From the results, the concentration of acetic acid influences the reaction rates of cathodic area. The main reaction in cathodic area is H_2 generation. Organic acids accelerate this reaction, and in the range from corrosion potential to H2O reduction potential, the polarization curve shows different behavior according to the weak acid concentration. Also, anodic reaction changed a little. The range from corrosion potential to pitting potential, the more concentration of acetic acids, the more goes down the anodic current density. Furthermore, acetic acids make the corrosion potential shift to positive potential. In addition, we examined the case of propionic acid, the difference appeared. Compared to acetic acid, it had more corrosive property to 13%Cr stainless steel. In the presentation, the outcome of weight loss experiment and the surface observation will be demonstrated.