Electrochemical corrosion behaviours of five Fe68Ni13-xMoxSi2B16 glasses with x = 0, 1, 2, 3 and 4 have been investigated in both 1 N HCl and 1 N H2SO4 solutions using potentiodynamic polarization and a.c. impedance spectroscopic techniques. The polarization and impedance results show that all the alloys possess inferior corrosion resistance which has been attributed to the low Ni content on one hand and the absence of passivators such as Cr and P on the other. Interestingly the alloys have been found to show weak passivation in more aggressive HCl and not in relatively mild H2SO4 solution. This has been explained in terms of dual behaviours of Mo in HCl and H2SO4 based on impedance data and literature work. The present study attempts to correlate impedance data with polarization data through the parameter polarization resistance and indicates that both values are comparable only when an alloy undergoes active dissolution and not when it exhibits passivity.