In-situ nano-indentation and scratching tests using a pyramidal Berkovich diamond indenter were performed to examine the nano-mechano-electrochemical properties of the passivated polycrystalline titanium surfaces. There were significant differences in the load-depth curves obtained between in-situ (kept at 5 V (RHE) in solution) and ex-situ (in air) nano-indentation tests at a maximum load of L-max = 300 muN for the titanium surfaces passivated at 5 V (RHE) for I h in pH 8.4 borate Solution. The hardness (9 GPa) of the passive titanium surface obtained from the in-situ load-depth curve was three or four times as large as that obtained from the ex-situ load-depth curve. The coefficient of friction for the passive titanium surface obtained from tile in-situ nanoscratching was also significantly larger than from that obtained from the ex-situ nano-scratching. The large differences in hardness and coefficient of friction between in-situ and ex-situ tests were discussed from the mechano-chemical viewpoint such as tile differences in repassivation rate at the film rupture sites near edge of contact area during indentation or near the front area of scratching between under potential control in solution and in air. (C) 2003 Elsevier Ltd. All rights reserved.