Interfacial Redox Regulation by Esterified Ascorbate Enables Corrosion-Suppressed Superlubricity

Abstract

Achieving liquid superlubricity while suppressing wear and corrosion remains a major challenge. In this work, we investigate ascorbic acid and its esterified derivatives as lubricant additives for steel/diamond-like carbon friction pairs. Although ascorbic acid achieves superlubricity (μ ≈ 0.008), friction-induced oxidation of its enediol groups generates corrosive products that accelerate wear. Density functional theory calculations reveal that esterification increases the oxidation barrier, inhibiting the formation of reactive intermediates. Guided by this strategy, L-ascorbyl 2,6-dibutyrate achieves stable superlubricity (μ ≈ 0.0038) while reducing the steel wear rate by over 68.2% to 5.88 × 10–9 mm3/N·m. Its superior performance arises from a stable adsorbed tribofilm and shear-induced molecular ordering of butyryl chains into a brush-like interfacial layer. This work establishes a molecular strategy for corrosion-resistant liquid superlubricity through interfacial redox regulation.