23rd International Colloquium Tribology - January 2022 345 Novel electrical current feed apparatus for aging simulation of lubricants Controlled electrical current feed and analytical analysis of lubricants and additives Yasmin Korth Dr. Tillwich GmbH Werner Stehr, Horb-Ahldorf, Germany Corresponding author: yasmin.korth@tillwich-stehr.com Susanne Beyer-Faiss Dr. Tillwich GmbH Werner Stehr, Horb-Ahldorf, Germany 1. Introduction Lubricants used in industrial applications consisting of baseoils and additive packages are mostly insulators and therefore not suitable to lead off electrical currents from e.g., friction bearings in cars. Adding conductive additives as ionic liquids has already been used in industrial applications [1]. But until now it is not clarified what will happen to the chemical structures exposed to these electrical currents. In this applied joint research approach [2] different ionic liquids with different conductivities and different model lubricants where exposed to well defined electrical currents using a new constructed equipment to examine the impacts of different voltages and exposing times using IR spectroscopy, rheology and conductivity measurements of the liquids. 2. Methods The ionic liquids and model lubricants were exposed to the shown current feed equipment (test chamber and oven), Figure 1. In the apparatus voltages from 0 to 25V are possible with different selectable polarization. The test chamber may be heated and the occurring conductivity can be metered. Figure 1: Test chamber and current feed apparatus 2.1 Infrared spectroscopy: The current feed samples were analyzed by using this spectroscopical method to characterize rearrangement and decomposition processes, example Figure 2. 2.2 Rheology: Measuring the changes in viscosity to determine the degradation progress have been performed. 2.3 Conductivity: Identifying the changes during the current feed operation was mapped. Figure 2: IR example spectra of a current feed ionic liquid and pictures of the current feed test chambers after 4 hrs, 24 hrs and 288 hrs. 3. Results The examined ionic liquids, chemically described as molten salts with no measurable vapor pressure are electrically conductive. Depending on their own conductivity they react on the applied voltage by degradation of 346 23rd International Colloquium Tribology - January 2022 Novel electrical current feed apparatus for aging simulation of lubricants their chemical structure and attacking the steel sample chambers depending on the composition of the used steel parts, even the PTFE distance ring can be affected. The conductivity decreases during the process as well as the measured viscosity afterwards leading to the assumption that the ionic liquids have been degraded by the voltage, Figures 3,4. Figure 3: Measured conductivies of different ILs before and after current feed. Figure 4: Measured viscosities of different ILs before and after current feed. Adding ILs to conventional lubricant baseoils in additive like concentrations, no corrosion at the steel parts are visible. In the IR-Spectra the ILs seems to “disappear” dissipated by the current feed. Conductivies are measurable and confirm the conductivies of the model lubricants, Figures 5. Figure 5: Measured conductivies of different ILs before and after current feed. Using 5% of the IL, the viscosity of the model lubricants are not influenced significantly, Figure 6. Figure 6: Measured viscosities of different model lubricants before and after current feed. 4. Conclusion Depending on their chemical structure, the ILs have been decomposed differently, taking also into account their viscosity and resulting conductivity. The corrosion potential only depends on the chemical structure of the ILs. Dissolving ILs into base oils in additive like concentration leads to conductivity of the fluid, depending on their solubility. The ILs are consumed without leading to corrosion. References [1] Khazalpour, S.et al., “Applications of phosphonium-based ionic liquids in chemical processes,” Journal of the Iranian Chemical Society, Review, Springer, 2020 [2] Joint research project EPiG: Development of electrically conductive lubricants and adapted nanocomposites for sliding bearings by use of ionic liquids and graphene. BMBF support code 03XP0220A. Duration 01.05.2019 to 30.04.2022