The corrosion inhibition of thiamine hydrochloride (vitamin B1) or biotin (vitamin B7) on corrosion of mild steel in 240 ppm chloride ions solution was studied using weight loss method, potentiodynamic polarization curves and electrochemical impedance spectroscopy. UV–Vis, FTIR and surface analysis using SEM and EDS characterization were carried out to understand the corrosion inhibition property of these inhibitors in 240 ppm aqueous chloride medium. Experimental results show that both thiamine hydrochloride and biotin act as a good corrosion inhibitors. Quantum chemical parameters obtained from density functional theory (DFT) calculations were discussed with experimental results.