Corrosion Inhibition Of 20R Steels In Desulfurization Solutions

In recent years,more and more deep sea gas fields in the South China Sea is needed to be developed,so a large number of FLNG?Floating Liquefied Natural Gas?are urgently needed to provide equipment and technical support for the exploitation of natural gas resources at sea.In order to remove the H₂S of the natural gas,FLNG must be equipped with sulfur recovery device for desulfurization.As the first batch of FLNG sulfur recovery unit in China,the desulfurization solution will result in the corrosion of the carbon steel during operation,so it's of great importance to inhibit the corrosion of the carbon steel in desulfurization solution.Electrochemical measurement was mainly used to investigate the corrosion inhibition of two imidazoline organic compounds?LED and ODD?and two inorganic compounds?SIA and SIB?for 20R steel in desulfurization solution systematically,and the influence of the Concentration of the target compound,temperature and medium flow rate on the corrosion process were studied.Then the optimized inhibitor was composited based on the corrosion inhibition behavior of the target compound.Finally,the corrosion inhibition effect was verified by dynamic weight less test and SEM test.The main contents of the paper are as follows:Potentiodynamic polarization results showed that the LED and ODD were mixed type inhibitor which mainly inhibit the anode process,and could inhibit the corrosion by absorbing on the surface of 20R steel.But the adsorption would affect the stability of the oxide film on the surface.So these two imidazoline inhibitors were not suitable for the corrosion inhibition of 20R steel in the desulfurization solution;SIA was a anodic type inhibitor and inhibited the corrosion by maintaining and repairing the oxide film on the surface of the anode;SIB was a mixed type inhibitor which mainly inhibit the anode process;The temperature range of these two inhibitors were wide,so they could be used for the corrosion inhibition of 20R steel in the desulfurization solution.Electrochemical impedance spectroscopy test results are consistent with the potentiodynamic polarization results.Considering the inhibition efficiency,compatibility,economic cost and safety,the paper selected SIA as the main agent,and then composited four corrosion inhibitors.Electrochemical measurement results showed that the composited inhibitor was mainly anodic type inhibitor;SIA formed a uniform,dense three-dimensional film on the surface of the carbon steel with iron oxide.The organic compound X₁ and Y could adsorb on the outermost layer of the membrane,and there was synergistic effect between the two.In the operation window with temperature of 40⁶0?and flow rate of 0.5¹.0 m/s,the corrosion inhibition efficiency of composited inhibitor FP-3 for 20R was 65%⁹8%,which had excellent corrosion inhibition effect,High stability and strong adaptability of the process.Dynamic weight loss test results verified the conclusion of the electrochemical measurement.The composited inhibitor FP-3 could maintain excellent corrosion inhibition effect under all test conditions with the corrosion inhibition efficiency achieving 48%⁹4%,and the corrosion rate of 20R was maintained at a very low level.The paper believe that the excellent performance of FP-3 can be attributed to the high stability of composited composition Y and its good synergistic effect with SIA.Considering the good corrosion inhibition effect of the composited inhibitor FP-3 for the 20R steel in the desulfurization soloution under various operating conditions,the paper recommend that FP-3 can be used to control the corrosion of FLNG sulfur recovery unit for 20R steel equipment effectively,reliablly and economically.