Effect of PWVA/Sb2O3 complex inhibitor on the corrosion behavior of carbon steel in 55%LiBr solution

The inhibition performance of PWVA/Sb2O3 complex inhibitor on carbon steel was studied in 55%LiBr + 0.07 mol L−1 LiOH solution. Results indicated that the complex inhibitor decreased both anodic and cathodic polarization current density and widened the passive potential region of carbon steel in test solution and can be classified as mixed inhibitor. The complex inhibitor exhibited excellent inhibition performance on carbon steel when the concentrations of PWVA and Sb2O3 were 300 and 200 mg L−1, respectively. With the solution temperature increasing from 145 to 240 °C, the corrosion rates of carbon steel increased from 4.71 to 120.66 μm y−1. In solution containing the complex inhibitor, the relationship between relative coverage ratio of inhibitor on carbon steel surface and inhibition efficiency at 145 °C was obtained as the equation μ = 0.94η, it was a direct proportion. This result proved that the complex inhibitor inhibited the corrosion of carbon steel by geometric blocking effect. When solution temperature was 160 °C, the adsorption Gibbs free energy of PWVA and Sb2O3 on carbon steel were −49.59 and −44.29 kJ mol−1, respectively. It indicated that the adsorption processes of PWVA and Sb2O3 on carbon steel surface were spontaneous processes. As a strong oxidant, PWVA facilitated the compact passive film comprising of FeO, Fe2O3 and Fe3O4 forming on the surface and itself was reduced to heteropoly blue. Sb2O3 adsorbed on carbon steel surface formed an adsorption film. PWVA and Sb2O3 behaved synergistic effect. The corrosion resistance performance of carbon steel in 55%LiBr + 0.07 mol L−1 LiOH solution was improved by PWVA/Sb2O3 complex inhibitor.