Extreme Pressure and Antiwear Behavior of Boronized Amine Salt of Thiophosphate as a Gear Oil Additive

A series of S-P type additives were synthesized in an attempt to find alternates as commercial multifunctional additive zinc dialkyldithiophosphates. The emphasis was placed on the synthesis of a multifunctional additive containing tribologically active elements S, P, N, and B, which was based on the boronization of the synthetic amine salt of thiophosphate. The extreme pressure and antiwear abilities of the synthetic additives were comparatively investigated using various commercial P-S type additives as the references, while the thermal stability and corrosion behavior of the synthetic compounds examined by means of thermogravimetric analysis and Cu strip corrosion test. It was found that the boronized amine salt of the thiophosphate as an additive in SAE90 oil showed much better extreme pressure and antiwear ability than the other two synthetic additives. It had better thermal stability and corrosion-resistance as well, which made it a promising candidate as a novel multifunctional ashless additive in gear oils and hydraulic oils.