Sodium sulfite as an oxygen scavenger for the corrosion control of mild steel in petroleum refinery wastewater: optimization, mathematical modeling, surface morphology and reaction kinetics studies

Abstract

Corrosion protection of mild steel in simulated refinery wastewater solution (2 wt% MgCl2) by sodium sulfite, as oxygen scavenger inhibitor type, was studied at different temperatures, inhibitor concentrations, rotational velocities and exposure times using weight loss and electrochemical techniques. Oxygen concentrations were also monitored at initial and final conditions. The corrosion inhibition process was optimized by 24 full factorial experimental designs. Optimum conditions of minimum corrosion rate were 40 °C, 40 ppm, 1250 rpm, and 6 h for temperature, inhibitor concentration, rotational velocity, and exposure time. Oxygen levels were reduced by the addition of the scavenger. The amount of oxygen reacted and removed during the corrosion process was evaluated and mathematical relationships were obtained. Electrochemical measurements showed that the corrosion potential shifted to the more active direction and corrosion current decreased with the addition of scavenger. Surface morphology investigations proved that the addition of SS prevents the steel surface damages.