Experimental evaluation of new inorganic phosphites as corrosion inhibitors for carbon steel in saline water from oil source wells

Corrosion inhibition potentials of three phosphites namely, M(HPO3) (where M = Mn, Co and Cu), for carbon steel in saline water from oil source wells were evaluated using weight loss and electrochemical impedance spectroscopy (EIS) methods. Characterization of the surface morphology was performed by SEM/EDX investigations. The corrosion rate of carbon steel in saline water decreased with increasing M(HPO3) concentration and increased with increasing temperature. M(HPO3) inhibits the corrosion of carbon steel by an adsorption mechanism, which follows Langmuir isotherm adsorption. The order of the inhibition efficiency of inhibitors is as follows: Mn(HPO3) < Co(HPO3) < Cu(HPO3). The thermodynamic functions of dissolution and adsorption processes were calculated and discussed.