Weight loss measurements and potentiostatic polarization studies show that tetrazospiro (5,5) undecane-3-thione (TUT) acts as an effective inhibitor for the corrosion of mild steel in 1 N HCl and 1 N H2SO4. This is also shown by hydrogen permeation studies by decreasing hydrogen permeation current through mild steel surface. Electrocapillary studies show that it is adsorbed on both the sides of the electrocapillary curves. It＇s adsorption on mild steel from 1 N HCl and 1 N H2SO4 is found to obey Temkin＇s adsorption isotherm.