The Importance of Temperature in Generating ZDDP Tribofilms Efficient at Preventing Hydrogen Permeation in Rolling Contacts

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

“…The comparison of the results in this paper and our previous experiments conducted at room temperature [14] show that the tribofilm effectiveness in preventing hydrogen permeation into the steel is strongly dependent on the temperature. This finding was also reported by Niste et al [10] and it was explained that the coverage of the surface by the tribofilm at low temperatures is inadequate to inhibit hydrogen permeation.…”

“…According to previous findings, elevated temperature accelerates ZDDP decomposition [40][41][42] and this appears to be a reason for the formation of a more uniform tribofilm in this study compared to the experiment results conducted at room temperature [14]. Niste et al [10] investigated the importance of temperature in generating ZDDP tribofilms and found that higher temperatures promoted uniform films that can exert a beneficial effect in reducing hydrogen permeation in rubbing contacts. This is in line with another study that found ZDDP chemisorption starts only above 50°C [43].…”

“…The characterization of the surface layer is important in determining the effect of the tribofilm on hydrogen permeation into the steel. It is believed that the wear track is the main entry point for the hydrogen to permeate into the steel whilst negligible amount of hydrogen can enter the substrate from outside the wear track due to the passive oxide layer covering the surface [10]. Therefore, the surface analysis was conducted within the track.…”

“…They attributed this behaviour to the presence of a complex WS2 tribofilm and its potential to impede hydrogen permeation. Recent publications also reported that, in optimum conditions of temperature, pressure and sliding, the ZDDP-generated tribofilm can hinder hydrogen entry into the steel [9,10]. The potential beneficial effects of DLC coating was also studied by Lu et al [2] and it was found that the coating could prevent hydrogen permeation by reducing friction and wear led to the less chemical composition of the lubricant.…”

Tribological behaviors of Ni-modified citric acid carbon quantum dot particles as a green additive in polyethylene glycol

“…Commercially available lubricant additives such as zinc dialkyl dithiophosphates (ZDDP) and molybdenum dialkyl dithiophosphates, which contain P, Mo, and S, are used as multifunctional additives. These additives have anti-wear, extreme pressure resistant, and antioxidant properties [4][5][6]. However, traditional lubricant additives are unfit for real-time applications owing to the strict environmental protection regulations [7].…”