Replacing non-renewable lubricants with vegetables oils in threaded joints

Lubrication is essential to ensure the proper performance of threaded joints subjected to multiple tightenings. Previous research has investigated the effectiveness of various mineral and synthetic lubricants, but no studies have been conducted on those derived from renewable sources. In this study, the performances of sesame, sunflower, coconut, and castor oil are compared to traditional VG46 oil and MoS${}_2$ grease. First, the rheological properties of the oils have been characterized. Then, tightening tests have been carried out to measure the coefficients of friction at the underhead and thread. The results demonstrate that vegetable oils outperform mineral VG46, especially in terms of repeatability. In particular, fractionated coconut oil exhibits exceptionally low coefficients of friction, which are not influenced by the tightening speed, unlike all other tested lubricants.