Protective properties of petroleum lubricating oils

Influence of humidity on the tribological performance of unmodified soybean and sunflower oils

“…This is consistent with other studies, and it has been suggested to be the result of the excess water in the mineral oil actually decreasing the operating viscosity, thus decreasing the film thickness to the point where metal‐to‐metal contact occurs . Other suggested reasons for this include the electrochemical corrosion influence of water and other constituents of the mineral oil on the metal and the fact that mineral oils cannot displace water from metal surfaces . Common mitigation techniques for these phenomena include the addition of low‐solubility corrosion inhibitors, additives to specifically mitigate the deleterious effects of water and the use of non‐ionic surfactants as emulsifying agents .…”

“…Other suggested reasons for this include the electrochemical corrosion influence of water and other constituents of the mineral oil on the metal and the fact that mineral oils cannot displace water from metal surfaces . Common mitigation techniques for these phenomena include the addition of low‐solubility corrosion inhibitors, additives to specifically mitigate the deleterious effects of water and the use of non‐ionic surfactants as emulsifying agents . However, such mitigation techniques would not be necessary for the vegetable oil stocks, as they already retain their high lubricity, low friction levels and good surface protection properties in an unmodified form at extremely high levels of relative humidity.…”

“…To reiterate, at such high level of saturation, it has been suggested that the viscosity of the mineral oil actually decreases, thus decreasing the film thickness to the point where metal‐to‐metal contact occurs . In addition, the mineral oil could introduce a higher degree of electrochemical corrosion with the presence of water and cannot easily displace water from the metal surfaces . Mitigation techniques for employment of mineral oil in extreme humidity environments include corrosion inhibitors, additives to specifically mitigate the deleterious effects of water and the use of non‐ionic surfactants as emulsifying agents .…”

“…In addition, the mineral oil could introduce a higher degree of electrochemical corrosion with the presence of water and cannot easily displace water from the metal surfaces . Mitigation techniques for employment of mineral oil in extreme humidity environments include corrosion inhibitors, additives to specifically mitigate the deleterious effects of water and the use of non‐ionic surfactants as emulsifying agents . The superior wear reduction properties of the unmodified vegetable oils when compared with the unformulated mineral oil indicate that the vegetable oil stocks would be a superior base stock for industrial applications involving high humidity levels and could possibly perform well even without modification.…”