Abstract
Tribology and corrosion engineering are both fields of engineering that deal with surface damage. This paper introduces lubricants, which occupy a significant area in the field of tribology, discussing market size, product composition, and more. Additionally, lubricants are composed of base oils to which additives are added, enhancing various properties. The role of lubricants in controlling friction and wear, cooling, preventing corrosion, removing and dispersing dirt, sealing, impact absorption, and power transmission is explained, focusing on engine oils. As base oils are refined, impurities are removed. The higher the purity of the base oil, the more effectively additives can perform their functions. This phenomenon is explained based on literature regarding the solubility state of additives in base oils. On the other hand, while viscosity and appearance are similar to oil-based products, there exists a aqueous glycol hydraulic fluid consisting of water-soluble components. In actual corrosion cases that occurred, it was necessary to employ different techniques compared to the aforementioned lubricants. Using knowledge from corrosion engineering, the causes and countermeasures were examined. By utilizing the concepts of depassivation pH and crevice repassivation potential, it was revealed that maintaining chloride concentration below 10 ppm can sustain passivation and prevent corrosion. The formation of passivity is also inferred to occur with oil-based lubricants, and detailed elucidation is awaited. Furthermore, there are practical challenges in increasing the limit concentration of chlorides in aqueous glycol hydraulic fluids. The progress of this technology will be discussed next time.
