Many Tribology Group publications are Open Access thanks to funding from the EPSRC.


BibTex format

author = {Dawczyk, J and Morgan, N and Russo, J and Spikes, H},
doi = {10.1007/s11249-019-1148-9},
journal = {Tribology Letters},
title = {Film thickness and friction of ZDDP tribofilms},
url = {},
volume = {67},
year = {2019}

RIS format (EndNote, RefMan)

AB - Tribofilm formation by several zinc dialkyl- and diaryldithiophosphate (ZDDP) solutions in thin film rolling-sliding conditions has been investigated. A primary, a secondary alkyl and a mixed alkyl ZDDP show similar rates of film formation and generate films typically 150 nm thick. Another secondary ZDDP forms a tribofilm much faster and the film is partially lost after extended rubbing. An aryl ZDDP forms a tribofilm much more slowly. The films all have a pad-like structure, characterised by flat pad regions separated by deep valleys. Three different techniques have been used to analyse the thickness and morphology of the tribofilms: spacer layer imaging (SLIM), scanning white light interferometry (SWLI) of the gold-coated film and contact mode atomic force microscopy (AFM). The SLIM method measures considerably thicker films than the other two techniques, probably because of lack of full conformity of a glass disc loaded against the rough tribofilm. No evidence of a highly viscous layer on top of the solid tribofilm is seen. SWLI and contact mode AFM measure similar film thicknesses. The importance of coating the tribofilm with a reflective layer prior to using SWLI is confirmed. As noted in previous work, the formation of a ZDDP tribofilm is accompanied by a marked shift in the Stribeck friction curve towards higher entrainment speed. For a given ZDDP this shift is found to correlate with the measured tribofilm roughness, proving that it results from the influence of this roughness on fluid entrainment in the inlet.
AU - Dawczyk,J
AU - Morgan,N
AU - Russo,J
AU - Spikes,H
DO - 10.1007/s11249-019-1148-9
PY - 2019///
SN - 1023-8883
TI - Film thickness and friction of ZDDP tribofilms
T2 - Tribology Letters
UR -
UR -
UR -
VL - 67
ER -