Investigation and testing of tailor-made lubricating oils for H2 applications

As part of the research project, the properties and requirements of lubricating oils for hydrogen applications were investigated. As a climate-friendly energy source, hydrogen exhibits significantly different combustion and operating conditions compared to conventional fuels, which creates new challenges for lubricants. Of particular relevance are, for example, high levels of water ingress due to hydrogen combustion, altered oxidation and nitration processes, and potential effects on wear, corrosion, and oil aging.
To investigate these issues, various base oils with different polarities and structures—including oils from API Groups II and III, PAO, ester, and PAG oils—as well as additive-containing test oils and fully formulated engine and compressor oils were analyzed. The study focused on the water and gas solubility, water separation capacity, changes in viscosity and density, interfacial tensions, foaming behavior, and oxidation and nitration stability of the lubricants in the presence of varying water contents.
The results show that, in particular, the chemical structure and polarity of the base oils have a decisive influence on the behavior of the lubricants during hydrogen operation. Polar lubricants such as PAGs and esters offer advantages in terms of water absorption capacity and water compatibility, but they also present different conditions regarding additive solubility and material compatibility. At the same time, it became clear that existing test methods are only partially applicable to hydrogen applications and must be modified or expanded.
The project thus provides an important foundation for the development of hydrogen-specific lubricants and testing methods. The findings are expected to facilitate the selection of suitable lubricating oils for H2 applications in the future, as well as contribute to the development of new lubricating oil concepts and to the reliable assessment of oil conditions during hydrogen operation.

IGF project 01IF22934N was funded by the Federal Ministry for Economic Affairs and Energy as part of the „Industrial Collaborative Research“ program, pursuant to a resolution of the German Bundestag.