The feasibility of using electrostatic monitoring to identify diesel lubricant additives and soot contamination interactions by factorial analysis

Electrostatic monitoring is a condition monitoring technique, which has been used for monitoring lubricated sliding contacts. The electrostatic charge is dependent on material wear and charge species in the lubricant (additives and contaminants). This paper presents work carried out on a pin-on-disc (PoD) tribometer to investigate additive–additive and additive–carbon black interactions. Online electrostatic charge and coefficient of friction (CoF) measurements were recorded. Post-test electro-kinetic sonic amplitude (ESA) measurements were taken and pin and disc material loss was measured using 3D profilometry. Statistical examination of results was conducted using Analysis of Variance (ANOVA) to reveal interactions. The primary conclusions include: primary zinc dialkyldithiophosphate (ZDDP) was found to increase pin wear due to immature antiwear film formation. Interactions between carbon black and detergent, and carbon black and dispersant, were observed in electrostatic charge data and ESA measurements. A complex between ZDDP and dispersant was highlighted by measured electrostatic charge, ESA, and pin material loss.