Electrochemical Investigation of Injection Rate of WS 86-1 Inhibitor on Corrosion of Carbon Steel API 5L Gr.B in Piping System of Nowrooz Offshore Complexes

In this study, the corrosion behavior of carbon steel API 5L Gr.B and injection rate of WS 86- 1 inhibitor was investigated in Piping System of Nowrooz Offshore Complexes. For this purpose, after immersion of samples at open circuit potential for 30 min, Tafel polarization and Electrochemical Impedance Spectroscopy (EIS) measurements were done. Tafel polarization curves showed that the minimum values for corrosion current density achieve at 40 ppm concentration of inhibitor. EIS results expressed that maximum values for polarization resistance achieve at 40 ppm concentration of inhibitor and demonstrated an agreement with the Tafel polarization results. Also, EIS results showed that the best electrical equivalent circuit presents two time constants. The first high frequencies time constant can be correlated with the charge transfer process and it is composed by the charge transfer resistance (R1) in parallel with the double layer constant phase element (Q1). While, the second low frequencies time constant can be related with the surface adsorption and it is composed by the adsorbed surface film resistance (R2) in parallel with the adsorbed surface film constant phase element (Q2).