Triggering\nthe Interplay of sp<sup>2</sup>–sp<sup>3</sup> Carbon-Assisted\nSustained Tribofilm via Two-Dimensional Surface\nModulation for Exceptional Wear Resistance of Steel Surfaces

The relentless wear and friction\nof steel-based moving\nmachinery\nhave created ongoing challenges that hinder their industrial applications.\nOne promising solution is the use of reduced graphene oxide (rGO)\nas a lubricant due to its excellent mechanical strength and promising\ntribological properties. However, its tendency to self-agglomerate\n presents a major hurdle for its practical use. This study aims to\ncombat the restacking of rGO nanosheets by strategically intercalating\nself-assembled α-ZrP between the rGO layers, unlocking exceptional\nwear resistance in mild steel through hot-dip galvanization. The multilayer\narchitecture of the developed coatings ensures lubrication through\nlayer slippage during friction, while the coexistence of sp<sup>2</sup>–sp<sup>3</sup> hybridized carbons further extends wear life,\nwith the Zn-0.22/ZP_5@G coating exhibiting the highest wear resistance\n(0.277 × 10<sup>–7</sup> mm<sup>3</sup> N<sup>–1</sup> m<sup>–1</sup>). The as-tailored composite coating, featuring\na tribolayer composed of graphitic sp<sup>2</sup> carbons, ZrO<sub>2</sub>, Zr(PO<sub>4</sub>)<sub>2</sub>, and Fe<sub>2</sub>O<sub>3</sub>, serves as an effective dissipative medium for contact stress.\nThe formation of diamond-like sp<sup>3</sup> carbons induced by the\ntribological process further contributes to the increased hardness\nof the resulting tribofilm. The reduced generation of the π-conjugated\nsystem in the composite prevents the movement of electrons toward\nthe cathodic site, while the passivation effect induced by the composite\neffectively inhibits electrolyte permeation, resulting in substantial\ncorrosion resistance. The exemplary wear resistance with remarkable\nanticorrosion performance achieved in this study offers significant\nimprovement in the realm of hard coatings for mechanical applications,\nincluding moving machinery and manufacturing. Hence, the system can\nfind effective use in such industries following the completion of\nrelevant case studies.