Corrosion inhibition of mild steel in hydrochloric acid solution by the expired Ampicillin drug

This study examines the utilization of the expired drug, namely ampicillin, as a mild steel corrosion inhibitor in an acidic environment. The inhibitor was evaluated using weight loss and electrochemical measurement accompanied with surface analytical techniques. The drug showed a potential inhibitory efficiency of > 95% at 55 °C. The inclusion of the inhibitor increased the charge transfer resistance at the steel-solution interface, according to impedance analyses. According to potentiodynamic polarisation measurements, expired ampicillin drug significantly decreased the corrosion current density and worked as a mixed-type corrosion inhibitor. The Langmuir adsorption isotherm was followed by the adsorption of ampicillin drug on the steel substrate, exhibiting an association of physical and chemical adsorption mechanisms. The surface study performed using contact angle and scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS) measurements supported the inhibitor adsorption on the steel substrate.