Overbased Calcium Dinonylnaphthalenesulfonate: Synthesis, Anti-Wear Performance, and Synergistic Lubrication-Electrochemical Inhibition Mechanism with ZDDP

Abstract

Oil-soluble overbased calcium dinonylnaphthalenesulfonate (OB-Ca-DNNS), with favorable anti-wear and acid-neutralizing capacities, was synthesized from dinonylnaphthalenesulfonic acid in this study. A four-ball tribometer was used to evaluate the tribological performance of OB-Ca-DNNS in PAO8 at mass fractions of 0.2 wt %–1.2 wt %. Its synergistic antiwear and corrosion inhibition performance, in combination with zinc dialkyldithiophosphate (ZDDP), was further explored. Combined SEM and EDS analyses were performed to characterize worn surface morphologies and elemental distributions, revealing the underlying antiwear mechanism. At the optimal addition level, OB-Ca-DNNS can reduce the friction coefficient. The optimal dosage of 0.8 wt % provided a wear scar diameter (WSD) of 0.56 mm for GCr15 bearing steel and reduced surface plowing, achieving a corrosion inhibition efficiency of 91.86% for Q235 steel. When compounded with 0.4 wt % ZDDP, the composite system achieved a WSD of 0.28 mm for GCr15 bearing steel and a corrosion inhibition efficiency of 95.14% for Q235 steel. During friction and corrosion inhibition, OB-Ca-DNNS cooperated with ZDDP to form a dense protective film dominated by CaO, FeS, and phosphates. This film isolated direct metal contact, thereby enhancing the synergistic antiwear performance and corrosion inhibition performance.