Lubrication and tribo-corrosion mechamisms of imidazolium based ionic liquid was explained. Regarding corrosion, molecular behavior of water which mixed with 1-buthyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM] OTf) under corrosion process has been investigated by Fourier Transform Infrared Spectroscopy (FT-IR). It was found that there are two mixture state of water in [BMIM] OTf; one is called free water, the other is called liquid-like water. Liquid-like water associates with corrosion. Then, we will mention the previous research of solid—liquid interface structure of ionic liquid and its contribution on friction. Finally, we will mention our recent results of relation between interfacial structure of adsorbed molecules and friction investigated by sum-frequency generation (SFG) spectroscopy.