ABSTRACT Corrosion mitigation of mild steel (MS) using the expired drug sodium hyaluronate (SH), as a green inhibitor, in 0.5 M HCl solution was evaluated by electrochemical methods and adsorption studies. Varied concentrations of SH drug (0.005, 0.01, 0.02, and 0.04 gL−1) were added and the corrosion rate (CR) of mild steel was measured at 303 and 308 K. Kinetic parameters were calculated and results were fitted into suitable adsorption isotherms. Contact angle measurement was used as a tool to understand the hydrophobicity of the material after the adsorption of the inhibitor. Adsorption of the inhibitor was confirmed by surface studies like scanning electron microscopy (SEM) and elemental dispersion analysis (EDX). A suitable mechanism was proposed for the adsorption of the inhibitor onto the surface of the material. The inhibition efficiency increased with an increase in the concentration of inhibitor and decreased with temperature. Using potentiodynamic polarisation data, a maximum inhibition efficiency of 91% in 0.5M HCl at 303 K and a concentration of 0.04 g/L SH was obtained. The inhibitor acted as a mixed type and obeyed the Langmuir adsorption isotherm. Contact angle measurement established the hydrophobicity of the MS surface after the addition of SH. Surface studies reaffirmed the adsorption of the inhibitor on the material. A suitable mechanism was proposed for the corrosion and inhibition process.