Acid Neutralization Number

“The neutralization number of an electrical insulating liquid is a measure of the acidic components of that material. In new oil, any acid present is likely residual from the petroleum refining process. In a service-aged liquid, the neutralization number is a measure of the acidic by-products of the oxidation of oil. The neutralization number may be used as a general guide for determining when oil should be reprocessed or replaced.”

(Quote from IEEE C57.106-2015)

What method is used to analyze the sample?


IEC 62021

How do you interpret the results?

IEEE C57.106-2015

What do the results indicate?

“New and used petroleum products can contain basic or acidic constituents that are present as additives or as degradation products formed during service, such as oxidation products. The relative amount of these materials can be determined by titrating with acids or bases. This number, whether expressed as acid number or base number, is a measure of the amount of acidic or basic substances, respectively, in the oil—always under the conditions of the test. This number is used as a guide in the quality control of lubricating oil formulations. It is also sometimes used as a measure of lubricant degradation in service; however, any condemning limits must be empirically established. Since a variety of oxidation products contribute to the acid number and the organic acids vary widely in corrosive properties, the test cannot be used to predict corrosiveness of an oil under service conditions. No general correlation is known between acid number and the corrosive tendency of oils toward metals.” (Quote from ASTM D974-21)

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