Electrochemical and theoretical evaluation of loratadine as corrosion inhibitor for X65 steel in 1M HCl aqueous solution

Currently oil industry infrastructure, mainly fabricated in carbon steel alloys, is exposed to aggressive environments due to the use of acid solutions during cleaning and maintenance operations, the search for eco friendly, economic and efficient protection alternatives is an active field of research in corrosion science. In this work the use of loratadine ($C_{22}{H}_{23}{\mathrm{ClN}}_2{O}_2$) as corrosion inhibitor for X65 steel in acidic media at room temperature is studied by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). Surface analysis was carried out using scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). Theoretical calculations (density functional theory, DFT) were used to elucidate the interaction between loratadine and an iron cluster model. Inhibitor efficiency increases with concentration reaching a maximum value of 93.69% according to PDP and 85.21% according to EIS. Thermodynamic analysis revealed that free energy of adsorption ($\Delta G_{ads}=-39.41$ kJ/mol) corresponds to a mixed adsorption process. Furthermore, the seven membered ring, pyridine and chlorophenyl groups were determined as the preferential active sites. Additionally, electrostatic interactions due to the transference from metal atoms to the organic molecules explains the physical interaction.