ToF‐SIMS analysis of phosphate‐type lubricant additives adsorbed on friction surfaces of ferrous materials

The adsorption of phosphate‐type lubricant additives on ferrous materials has been investigated by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) of friction surfaces. Eight kinds of model compounds were used for the friction tests. In ToF‐SIMS spectra of the friction surfaces after washing with hexane, Fe‐alcoholates were detected as reaction products of alcohol units of the additives and the ferrous material, and Fe‐polyphosphate was detected as a reaction product of a phosphate unit and the ferrous material. The quasi‐molecular ions of model compounds, which suggest the existence of physical adsorption, were detected in some of the lubricant systems. The amounts of these products were found to be correlated with lubrication properties such as friction coefficient and width of wear scar.