The purpose of this study is to investigate the electrochemical properties of the Co(1.5)CrFeNi(1.5)Ti(0.5)Mo(x) high-entropy alloys in three aqueous environments which simulate acidic, marine, and basic environments at ambient temperature (similar to 25 degrees C). The potentiodynamic polarisation curves of the Co(1.5)CrFeNi(1.5)Ti(0.5)Mo(x), alloys, obtained in aqueous solutions of H(2)SO(4) and NaOH, clearly revealed that the corrosion resistance of the Mo-free alloy was superior to that of the Mo-containing alloys. On the other hand, the lack of hysteresis in cyclic polarisation tests and SEM micrographs confirmed that the Mo-containing alloys are not susceptible to pitting corrosion in NaCl solution. (C) 2010 Elsevier Ltd. All rights reserved.