The performance and antiwear mechanism of S‐containing organic borate as an oil additive

A sulphur‐containing organic borate (BS‐2) was prepared. Its friction and wear properties when added to n‐tetradecane, and the effect on wear of addition of dodecyl amine to the synthesised S‐containing borate oil, were measured using a Timken test machine. The results were compared with those of tridodecyl borate, and a combination of tridodecyl borate and sulphurised cotton seed oil. X‐ray Photoelectron Spectroscopy (XPS) was used to examine the rubbed surfaces of the test blocks, while Scanning Electron Microscopy (SEM), Energy Dispersion Analysis of X‐ray (EDAX) and X‐ray Diffraction (XRD) were used to study the wear debris. It is found that S‐containing organic borate exhibits a poorer antiwear property than tridodecyl borate but, with the addition of dodecyl amine to the S‐containing borate, its antiwear property can be improved. XPS analyses indicate that sulphur on the rubbed surfaces exists in the forms of organic sulphide and FeSO₄, and the addition of amine reduces the adsorption and reaction of sulphur to the rubbing surfaces. SEM analyses revealed that the wear debris was in powder form, and the EDAX and XRD analyses indicated that iron sulphide, iron oxide and elemental iron were contained in the wear debris. A corrosive wear mechanism of steel test blocks lubricated by S‐containing organic borate is proposed.