The Rhodanine inhibition effect on the corrosion of a mild steel in acid along the exposure time

The corrosion performance of a mild steel (MS) exposed to a 0.5 M HCl solution with various concentrations of Rhodanine (Rh) was studied by means of anodic and cathodic voltammetric curves, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. Rh makes the corrosion of MS in HCl solution decelerate with the exposure time so as to reach a protective value of more than 99% in 168 h. The adsorption of Rh molecules on the MS obeys Langmiur adsorption isotherm. Thermodynamic parameters, adsorption equilibrium constant (K _ads), and standard free energy of adsorption (ΔG _ads ^o ) were calculated and discussed. The high inhibition efficiency was discussed in terms of blockading the metal surface by the Rh molecules strongly adsorbing witch their active centers and thus forming a sufficiently effective protective film.