Within the DESSERT project, AC2T research GmbH investigated the stability of two lubricants for threaded connections under hydrogen exposure. The results show that both lubricants remained chemically stable, supporting the development of reliable and more sustainable solutions for hydrogen underground storage.
Lubricants in threaded connections must avoid galling and ensure the correct level of friction during make-up of the connection. But additionally, they must stay stable during the service life of the tubes and connections. This means the employed lubricants must not be altered by the hydrogen environment.
Investigated lubricants
Two different lubricants were selected for further analysis and provided by Tubacex Innovación. One of the lubricants was a grade of API modified which is a well-established standard product in the oil and gas industry. This lubricant is based on conventional petrochemical products with a high content of solid lubricant particles such as graphite, copper, zinc and lead. In particular, around 30% of its content is lead, an environmentally harmful substance.
Therefore, a novel green lubricant was investigated and tested as alternative. This lubricant is based on ester base oil containing mineral particles in its composition. The tribological suitability and galling resistance for both lubricants was investigated within DESSERT by Fundación Tekniker.
Testing and qualification
For both lubricants, test series comprising long term exposure of the lubricant to hydrogen within a gas solubility test chamber with subsequent chemical and rheological analysis were performed. Both lubricants showed similar results where a significant amount of gas uptake was measured with the gas solubility test chamber and foaming was observed. Immediately after removal of the specimen from the gas solubility test chamber, analysis with heating of the samples and analysis of the outgassing species employing high-resolution mass spectrometry were performed. These measurements detected no significant dissolved hydrogen in the specimen at ambient conditions. Also, chemical analysis with infrared spectroscopy and measurements of the rheological properties showed no alteration of the lubricants due to hydrogen exposure.
This proves that both lubricants are stable in hydrogen atmosphere and hydrogen is only physically dissolved without any lasting effect or chemical alteration of the lubricant.
