Inhibition of Iron-Catalyzed Neopentyl Polyol Ester Thermal Degradation Through Passivation of the Active Metal Surface by Tricresyl Phosphate

Abstract

To investigate the role of tricresyl phosphate (TCP) in inhibiting the iron-catalyzed thermal degradation of a neopentyl polyol ester gas turbine lubricant base stock, various TCP/ester combinations were encapsulated in mild steel tubing and heated at 500 F up to 96 hours. The relative degradation rates of the individual mixtures were measured by monitoring the effusion site of hydrogen (a degradation byproduct) through the capsule all. The capsule interiors were then examined by electron microscopy and diffraction to determine whether correlation assisted between the features of the surface films formed and the reserved degradation rates.

Distinctive films were produced in each test mixture. When ester degradation was inhibited by the addition of 2–10% TCP, characteristic iron oxide layer was always found at the ester/steel interface. It was postulated that TCP induces the formation of this film, that the film is the agency of inhibition, and that it is similar in action and genesis to the iron oxide passive films known in aqueous systems.

Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Houston, Texas, October 14–16, 1969

Notes

Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Houston, Texas, October 14–16, 1969