Multidentate Cyclohexylphosphonic Acid as Corrosion Inhibitor for Structural Steel in 3.5% NaCl Solution: An Experimental and Computational Study

The inhibition effect of cyclohexylphosphonic acid (CHPA) on the corrosion of structural steel (EN 10027) in 3.5% sodium chloride solution has been studied by using potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) technique and weight loss measurements for a wide enough temperature range (298-328 K). Electrochemical results confirmed that the examined inhibitor can effectively suppress the structural steel corrosion in 3.5% sodium chloride solution with an inhibition efficiency of 93% after 30 min of immersion. Potentiodynamic polarization results revealed that CHPA is a well mixed-type inhibitor, and its adsorption on structural steel surface in 3.5% NaCl-fulfilled with the Langmuir isotherm. Both chemi-and physisorption of CHPA take place on the structural steel, resulting in the formation of a protective layer, which was evidenced by SEM observations. Density functional theory and molecular dynamics (MD) were carried out to clarify the inhibitor/metal interactions.