An investigation of effect of MDEA on API 5L X65 corrosion in Na2S & CO2 solution with electrochemical noise analysis

In this study, API 5L X65, which is widely used in gas pipelines was selected. Electrochemical potential and current noise tests have been carried out on this alloy, in a solution containing 0.5 % Na S and in the presence of CO2 gas. Moreover, the effect of Methyl Diethanol Amine (MDEA) addition into the test solution was studied. MDEA is used in the petroleum industry as a H2S and CO2 removal, as well as for controlling pH. The mentioned solution is a simulator solution for the sour gas fluid in the gas transmission pipelines in South Pars Gas Company. The XRD results revealed the formation of same FeS layer in the simulator solution and in the field study. Prior to electrochemical noise data analysis, DC trend removal had been carried out. The results showed X65 samples were reached to optimum condition of general and localized corrosion after addition of an optimum amount of MDEA into the simulator solution. The optimum amount of MDEA was 300 ppm, which results in optimized corrosion resistance.