The behaviour of some 3-methyl-1-butyne halo-derivatives towards Armco iron corrosion in 0.5 M H2SO4 was examined by the analysis of dissolved iron and electrochemical methods. Their inhibitive performance was determined in relation to the introduced halogen atom with respect to the duration of the tests and temperature. At the same time, these effects were compared to those of 1-octyn-3-ol. In general, the results of the electrochemical methods were found to be in good agreement with those of solution analysis. The possibility of obtaining reliable corrosion data from electrochemical impedance spectroscopy measurements by simply applying the Stern-Geary equation is discussed.