The inhibitive effect of fenugreek (Trigonella foenum graecum) seeds extract on the corrosion of zinc in aqueous solution of 0.5M sulphuric acid were investigated at 30, 35, 40 and 45°C by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization curves indicated that the fenugreek seeds extract behaves as an anodic type inhibitor. EIS measurements showed that the dissolution process occurs under activation control. Inhibition was found to increase with increasing concentration of the fenugreek seeds extract but decreases with increasing temperature. The associated activation parameters were determined and the results showed that the fenugreek seeds extract could serve as an effective inhibitor for the corrosion of zinc in sulphuric acid media at higher temperature. The influence of exposure time on the performance of fenugreek seeds extract was investigated. Results showed that the extract performed well after an induction period that is required to release zinc ions in solution in stoichiometric ratio necessary to form stable adsorbed complex with the chemical constituents of the extract.
