Corrosion behaviors and post-corrosion wear mechanisms of lubricants containing multiple additives under H₂-air exposure

Hydrogen internal combustion engines represent a critical power unit for the transition from conventional fossil fuels to zero-carbon energy in the transportation sector. However, the lubricants protecting metal parts are prone to contact with unburned hydrogen and oxygen during operation. The changes in lubrication performance and corrosion characteristics of lubricants containing different additives after prolonged exposure to these gases have not been thoroughly investigated. In this study, lubricants containing phosphate ester, diphenylamine, zinc dialkyldithiophosphate (ZDDP), and basic ZDDP were subjected to corrosive tests by flowing air or hydrogen at controlled rates over metal and steel coupons, respectively. The corrosive behaviors of the testing coupons and the wear mechanisms of the post-corrosion lubricants were analyzed. The results show that oils containing phosphate ester and diphenylamine caused more corrosion on the coupons. Energy-dispersive spectroscopy, inductively coupled plasma, and gas chromatography-mass spectrometry confirmed that introducing hydrogen during corrosion significantly reduced oxidative corrosion on the coupons and mitigated the degradation of antioxidant additive components. Under 12 lph flow rates of hydrogen, the diphenylamine-containing post-corrosion lubricants exhibited 21 % lower average friction coefficient, and the ZDDP-containing post-corrosion lubricants showed 10 % shallower in wear scars compared to their raw oil. The enhanced lubricity is attributed to the hydrogen-introduced corrosion process, which facilitates the formation of composite oxide layer comprised of Fe–FeO–Fe₂O₃–FeOOH, and tribofilm containing zinc phosphate ester and zinc sulfide, respectively. The H₂-introducing corrosion-tribology test is an accelerated practical method for assessing long-term lubrication in hydrogen combustion engine environments, aiding lubricant formulation and design.