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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.

The adsorption of model compounds of friction modifiers on ferrous materials has been investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Eleven kinds of model compounds, including carboxylic acids, alcohols, amines and esters, were subjected to lubrication tests. Six compounds among these -carboxylic acids and some amines and esters -showed good lubricity. The ToF-SIMS spectra of the friction surfaces after being washed with hexane showed that carboxylic acids formed Fe-carboxylates by reacting with the ferrous material, and esters formed both Fe-carboxylates and Fe-alcoholates by reactions of hydrolysates of esters and the ferrous material. For amines, no reaction products were detected but quasimolecular ions, suggesting physical adsorption, were detected from the friction surfaces. For alcohols, no adsorption or reaction was detected from the friction surface. However, clear correlations were not found between the amounts of reaction products or adsorbed materials and lubrication properties such as friction coefficient and width of wear scar.