7. Oxidation resistance

Under the combined action of atmospheric oxygen and temperature, hydrocarbon molecules and synthetic fluids oxidize, transforming into a series of more or less polymerized oxygenated products, some of which have an acidic function. The phenomenon evolves as a function of time, as shown in figure 17 . An induction phase, during which the process is slow, is followed by a phase of rapid evolution corresponding to severe oxidation. The phenomenon is accelerated by the presence of catalysts: metallic particles of iron, copper, oxides and so on.