This work investigates the effect of amines on the lubricity of castor oil-sulfated sodium salt (CSS) emulsion solution for titanium alloys. It is found that the amines with hydrophilic parts such as diglycolamine, have a negative effect on the lubrication while those with hydrophobic parts such as dicyclohexylamine (DCHA), show a synergistic effect when they are mixed with the CSS. The mechanisms of both the synergistic and negative effects of amines are investigated. The quartz crystal microbalance with dissipation-monitoring results show that the ammonium salt with hydrophobic parts such as DCHA can form a strong adsorption film on the titanium surface. These findings indicate that the amines with hydrophobic parts can be used as a pH regulator and corrosion inhibitor for developing an effective cutting fluid for titanium alloys.
