Experimental and computational study of penicillamine drug and cysteine as water-soluble green corrosion inhibitors of mild steel

Abstract

Cysteine amino acid is well known as an effective green corrosion inhibitor. Due to the structural similarity between d-penicillamine (PA) drug and cysteine, it is expected PA also acts as a green corrosion inhibitor. Herein we describe the corrosion inhibition ability of PA and l-cysteine (Cys) on the mild steel in 1 M HCl using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Experiments were performed in various concentrations of Cys and PA and different immersion times. The results suggested that both Cys and PA can be used as effective corrosion inhibitors. PA and Cys are mixed-type inhibitors; however, PA affected significantly only the cathodic reaction. The adsorption of inhibitors followed the Langmuir adsorption isotherm. Electronic structure of Cys and PA was elucidated with density functional theory (DFT) calculations. Molecular adsorption on Fe(110) was investigated using molecular dynamics (MD) simulations.