Evaluation of corrosion inhibitors for P110 steel in simulated oilfield producedwaters using EFM and CMAS techniques

Inhibition performance of a complex inhibitor of bis-quaternary ammonium and thiourea (with mass fraction 1∶1) for the serious corrosion of P110 steel in simulated oilfield produced waters was studied by means of techniques of mass loss, electrochemical frequency modulation (EFM) and coupled multielectrode array sensors (CMAS). Experimental results indicate that this inhibitor could inhibit P110 steel from CO₂ corrosion efficiently. The inhibition efficiency was up to 95.31% when the concentration of inhibitor was 150 mg/L at 60 ℃. The inhibition efficiency decreased at 90 ℃, however, the inhibitor could eliminate the pitting corrosion of P110 efficaciously. EFM and CMAS techniques could monitor the corrosion process of the steel and evaluate the effectiveness of the inhibitor. The deviation from theoretical value of causality factor of EFM could reveal the effectiveness of the addition of inhibitor, i.e. the inhibitor could protect P110 from pitting corrosion. The results of CMAS showed that the prevention of pitting corrosion could be attributed to the adsorbing of inhibitor on the steel surface to relieve the concentrated distribution of cathodic and anodic currents.