Insight into corrosion inhibition mechanism of carbon steel in 2 M HCl electrolyte by eco-friendly based pharmaceutical drugs

Abstract

Carbon steel alloys are the usual materials in petroleum refining facilities. However, poor corrosion resistance of carbon steel is a serious problem for the use of its alloys in the petroleum industries. Herein, we demonstrate the use of pharmaceutical drugs namely; levofloxacin, moxifloxacin, metolazone, and nifedipine for enhancing carbon steel resistance in 2 M HCl solution using mass loss, electrochemical impedance spectroscopy, potentiodynamic polarization, computational studies, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The order of average corrosion inhibition efficiency of the studied compounds are Meto>Levo>Moxi>Nife. This order is in agreement with the polarization, mass loss, and theoretical measurements. The morphological studies from SEM and AFM revealed that the tested compounds could effectively enhance carbon steel resistance through adsorption on the metal surface. The adsorption behavior follows Langmuir, Temkin, El-awady, Frumkin, and Flory- Huggins adsorption isotherms. The computational studies using DFT simulation revealed the mechanisms of inhibition performances of the inhibitors on the carbon steel corrosion. The quantitative structure-activity relationship (QSAR) approach provides a clear definition of some measured quantum chemical parameters needed to align with the inhibitors’ inhibition efficiencies that were determined experimentally. Mulliken population analysis revealed the atoms that are responsible for adsorption on the surface of carbon steel. The present investigation provides new insight into the usefulness of these drugs in corrosion mitigation.