1.1 This test method covers procedures for the determination of initial pH (i-pH) in lubricants. NOTE 1-In new and used oils, the constituents that may be considered to have characteristics influencing the i-pH value include organic and inorganic acids, esters, phenolic compounds, lactones, resins, salts of heavy metals, salts of ammonia and other weak bases, acid salts of polybasic acids, and addition agents such as inhibitors and detergents. 1.2 This test method is used to indicate relative changes that occur in oil during use under oxidizing conditions or as a result of contamination by blow-by gases of combustion processes of biogases regardless of the color or other properties of the in-service lubricants. Although the initial pH is made under definite equilibrium conditions, this test method is not intended to measure an absolute acidic property that can be used to predict performance of oil under service conditions. No general correlation between corrosion of nonferrous bearing metals and initial pH value is known. 1.3 The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
This standard is requested by OEM engine manufacturers who base their oil change intervals on pH values. The measured value provides valuable information on the acidity of test samples and is used as one criteria for when to change the lubricant.
Keywordsi-pH value; lubricants; petroleum products; potentiometric
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
Ballot Item Approved as D7946-2014 and Pending Publication