Robust Superhydrophobic Membrane for Solving Water-Accelerated Fatigue of ZDDP-Containing Lubricating Oils

Superwetting materials show distinct advantages in interfacial applications such as oil-water separation. However, it remains a challenge to solve water-accelerated fatigue of lubricating oils owing to the poor mechanical durability of superhydrophobic surfaces and the intractable emulsions stabilized by additives. In this work, a robust superhydrophobic membrane for solving water-accelerated fatigue of lubricating oils containing zinc dialkyldithiophosphate (ZDDP) as a typical antiwear additive is presented. An all-inorganic coating is constructed by SiO₂ nanoparticles and aluminum phosphate using a simple spray-coating method. After silanization, the prepared membrane can extremely repel water and effectively separate ZDDP-stabilized water-in-lubricating oil emulsions (the purities of the collected lubricating oils are over 99.995%), even after sand impingement for 100 cycles. Ball-on-disk tribological tests at severe contact pressures reveal that the reclaimed lubricating oils recover the protective ability, and the catalytic dehydrogenation of lubricating oil is dramatically suppressed to avoid producing a mass of unwanted carbon-based wear debris. This work advances the development of superwetting materials in the lubricating oil industry.