Infrared Spectroscopy as a Tool for Monitoring Oil Degradation

Oxidative and thermal degradation of lubricating oils are complex processes. While the fundamental chain reaction mechanisms are known, the actual chemistry of a formulation involving several additives still remains a gray area. An understanding of some of the additive interactions and their degradation pathways will ultimately lead to a more scientific approach to formulation optimization for a given application. Current methodology involves laboratory bench tests as a screening mechanism before the more expensive mechanical tests are used for the evaluation of a final lubricant formulation. This is particularly the case for automotive and gas turbine lubricants. The chemistry linking the bench test and the mechanical tests to the oil formulation are rarely considered.

This paper will illustrate how modern infrared spectroscopy can be used to monitor lubricant degradation. Also, it will demonstrate by simple applications, that the technique has the potential of providing much of the information required to follow the chemical reactions that are involved.