The multiple roles of a chemical tribofilm in hydrogen uptake from lubricated rubbing contacts

A newly developed in-situ technique has been employed to investigate the effect of lubricant additives and water contamination in oil on hydrogen intrusion into the steel. Hydrogen in oil-lubricated contacts is generated as a result of tribochemical reactions. The hydrogen uptake measurement results indicated that tribofilm formation can impede hydrogen ingress, in the substrate, by impeding the formation of fresh metal surfaces. This reduces the generation of hydrogen atoms by preventing the decomposition of hydrocarbon molecules. A uniform tribofilm across the wear track also acts as a physical barrier for hydrogen permeating through the tribo-contact. The water contamination in the oil negatively influenced tribofilm properties and therefore led to higher permeation of hydrogen into the steel.