The dissolution of aluminium in 2N hydrochloric acid solution is retarded by the addition of some 1,3,4-thiodiazole derivatives to the medium. Three different techniques, viz., weight loss, gasometric and thermometric are applied. Temperature effect has been investigated in the range 25-40 degrees C and the activation energies have been calculated. The inhibition efficiency decreases with the rise in temperature while the activation energy increases in the presence of the additives. The inhibitive character of the additives depends on the concentration as well as the composition of the inhibitor.