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ToF‐SIMS analysis of model compounds of friction modifier adsorbed onto friction surfaces of ferrous materials

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. Copyright © 2001 John Wiley & Sons, Ltd.