How oxidation changes oil
Once the oxidation process occurs, five major changes in the oil result in the following:
- Colour becomes darker – changes from transparent or translucent in colour to some degree of discoloration toward the point of complete opacity.
- Odour becomes pungent and acetic due to the presence of excessive organic petroleum acid and similar products of oxidation.
- Acidity increases – changes from a neutralisation number from 0.06 to 0.12 KOH mg/g to well above 2.0 can occur.
- Viscosity increases – the viscosity of an oil frequently may double or triple due to oxidation. Oxidative thickening is capable of producing fluids that have the consistency of molasses-like sludge under high operating temperature conditions.
- Insolubles precipitate (sludging occurs) – after an induction period, the deterioration of an oil gradually accelerates until the formation of organic acids of deposition of sludge completely destroys the oil.
Courtesy of Noria Corporation.