Streptomycin for corrosion inhibition of mild steel in sulfamic acid: experimental and computational investigations

The corrosion inhibition capability of the near-expiry date drug streptomycin (STN) was tested as a green inhibitor for controlling the corrosion of mild steel (MS) in sulfamic acid (NH₂SO₃H). Experiments were performed using electrochemical techniques such as potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). Kinetic and thermodynamic parameters were evaluated to predict the mode of adsorption of STN on the Mild steel surface. Adhesion of the STN was confirmed by surface morphology studies using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Density functional theory was adopted to determine various quantum chemical descriptors. Streptomycin was found to be efficient while bringing down the corrosion rate. It acted as a mixed-type inhibitor, underwent physical adsorption, and followed the Langmuir adsorption isotherm. At 303 K and 0.05 g l⁻¹ STN concentration, the maximum inhibition efficiency was found to be 60%. The quantum calculations and the results of the electrochemical studies correlated well with one another. Unused near-expiry date drugs have emerged as environmentally conscious and efficient green inhibitors.