In situ, real time studies of thermal reaction film formation temperatures for iron and 304SS surfaces immersed in 5% tricresyl phosphate in base oil

The temperature at which TCP forms a thermal reaction film with Fe and 304SS surfaces has been measured in real time, in situ liquid environments utilizing a QCM immersed in a synthetic dibasic ester base stock containing 5% TCP, and observed to be 210 °C. The thermal reaction films were characterized by AFM, and observed to be uniform on Fe and non-uniform and nodular in nature on 304SS substrates, with the thicknesses in the range of 60-100 nm. The chemical composition of the thermal reaction films was studied with EDS. The methods employed here demonstrate an effective means for screening of reaction film formation, and are extendable to systems involving multiple additives and/or complex metal composite materials.