ASTM D7751 - 11 standard test method for determination of additive elements in lubricating oils by edxrf analysis

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Source: ASTM International

Lubricating oils are formulated with organo-metallic additives, which act, for example, as detergents, antioxidants, antifoaming, or antiwear agents, or a combination thereof. Some of these additives contain one or more of the following elements: magnesium, phosphorus, sulfur, chlorine, calcium, zinc, and molybdenum. This test method provides a means of determining the concentrations of these elements, which in turn provides an indication of the additive content of these oils.

Additive packages are the concentrates that are used to blend lubricating oils.

This test method is primarily intended to be used for the monitoring of additive elements in lubricating oils.

If this test method is applied to lubricating oils with matrices significantly different from the calibration materials specified in this test method, the cautions and recommendations in Section 6 should be observed when interpreting the results.

1. Scope

1.1 This test method covers the quantitative determination of additive elements in unused lubricating oils and additive packages, as shown in Table 1. The pooled limit of quantitation of this test method as obtained by statistical analysis of interlaboratory test results is 0.02% for magnesium, 0.003 % for phosphorus, 0.002 % for sulfur, 0.001 % for chlorine, 0.003 % for calcium, 0.001 % for zinc, and 0.002 % for molybdenum.

1.2 Additive packages require dilution with a contamination free diluent (base oil) prior to analysis. The dilution factor has to be calculated from the expected concentrations to bring the concentrations for all elements into the ranges listed in Table 1.

1.3 Some lubrication oils will contain higher concentrations than the maximum concentrations listed in Table 1. These samples require dilution with a contamination free diluent (base oil) prior to analysis. The dilution factor has to be calculated from the expected concentrations to bring the concentrations for all elements into the ranges listed in Table 1.

1.4 This test method is limited to the use of energy dispersive X-ray fluorescence (EDXRF) spectrometers employing an X-ray tube for excitation in conjunction with the ability to separate the signals of adjacent elements by using a high resolution semiconductor detector.

1.5 This test method uses inter-element correction factors calculated from a fundamental parameters (FP) approach or from another matrix correction method.

1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6.1 The preferred concentration units are mg/kg or mass %.

1.7 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.

TABLE 1 Elements and Range of Applicability

Index Terms

additive elements; additives; calcium; chlorine; EDXRF; energy dispersive; lubricating oil; magnesium; molybdenum; phosphorus; spectrometry; sulfur; X-ray; XRF; zinc

ICS Code

DOI: 10.1520/D7751-11

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