Sources of Phosphorus

Phosphorus is an additive metal found in all anti-wear (AW) and extreme pressure (EP) additive packages. Only when the phosphorus level deviates more than 25% from the new oil or reference value should a concern be raised, but the likeliest cause is mixing or topping-off with a different product. AW oils can be differentiated from EP oils, as AW oils contain zinc, at comparable levels, whereas EP typically contains no or low levels of zinc. With normal and expected additive depletion due to usage, the additives are still present in the fluid, and will still be measured at their normal levels. Once they do not appear in the fluid, they have dropped out completely, which indicates a more severe degradation mechanism or additive drop-out. Phosphorus may appear due to grease contamination, as general-purpose greases also contain AW or EP additive packages. Machines with greased seals or those having undergone recent maintenance may exhibit small increases in phosphorus, depending on the rate of leakage or overage in use. Another form of maintenance that may lead to an increase in phosphorus levels is through the use of degreasing chemicals, either from equipment or parts washing. Some degreasers are phosphate-based and may enter a machine during high-pressure wash-downs, or be residual contamination from aqueous degreasers used in parts washers. Watch for the next article in the Elemental Spectroscopy blog series: Zinc

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