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As engine oils continue in service, combustion gases combine with the oil resulting in the formation of acids that are corrosive to the surfaces with which they come in contact. Sulfur in fuel may cause the formation of strong sulfuric acid. Alkaline additives are used to neutralize this effect. The reserve alkalinity or the remaining ability of these basic compounds to neutralize acidic compounds is measured by the total base number (TBN) of the oil. Sulfation correlates inversely with TBN. Sulfation as determined with an infrared spectrometer, such as the Spectro FTIR or FluidScan, is a measure of the decline of a lubricant's ability to combat acidity. It complies with ASTM E 2412.
For specific oils in specific applications it is possible to use IR spectroscopy as a direct measure of TBN. This is done by using a partial least squares regression of the spectra of numerous samples in which the TBN has been determined by standard analytical methods.
Applicable Spectro Products: