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The inhibitory effect of Eremomastax polysperma leaf extract on aluminium corrosion in hydrochloric acid solution was investigated using weight loss and thermometric methods. Analyses of the experimental data show that the inhibition efficiency increased with increase in Eremomastax polysperma leaf extract concentration and decrease in temperature. The highest inhibition efficiency of 81.78% occurred at 4.0 g/L extract concentration at 30°C by weight loss measurements. The adsorption of the leaf extract on aluminium surface is proposed to occur via physisorption mode. The experimental data fit the modified Langmuir isotherm. The negative values of ΔG°ads obtained reveal the spontaneity of the adsorption process while the positive values of ΔH°ads indicate that the adsorption of Eremomastax polysperma leaf extract on aluminium surface was an endothermic process.