ASTM D6186-98(2003)e1
(Test Method)Standard Test Method for Oxidation Induction Time of Lubricating Oils by Pressure Differential Scanning Calorimetry (PDSC)
Standard Test Method for Oxidation Induction Time of Lubricating Oils by Pressure Differential Scanning Calorimetry (PDSC)
SIGNIFICANCE AND USE
Oxidation induction time, as determined under the conditions of this test method, may be used as an indication of oxidation stability.2 This test method is faster than other oil oxidation tests and requires a very small amount of sample. It may be used for research and development, quality control, and specification purposes. However, no correlation has been established between the results of this test method and service performance.
SCOPE
1.1 This test method covers the determination of oxidation induction time of lubricating oils subjected to oxygen at 3.5 MPa (500 psig) and temperatures between 130 and 210°C.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 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.
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An American National Standard
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Designation:D6186–98 (Reapproved 2003)
Standard Test Method for
Oxidation Induction Time of Lubricating Oils by Pressure
Differential Scanning Calorimetry (PDSC)
This standard is issued under the fixed designation D 6186; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Warning notes were editorially moved into the standard text in August 2003.
1. Scope 4. Significance and Use
1.1 This test method covers the determination of oxidation 4.1 Oxidation induction time, as determined under the
induction time of lubricating oils subjected to oxygen at 3.5 conditions of this test method, may be used as an indication of
MPa (500 psig) and temperatures between 130 and 210°C. oxidation stability. This test method is faster than other oil
1.2 The values stated in SI units are to be regarded as the oxidation tests and requires a very small amount of sample. It
standard. maybeusedforresearchanddevelopment,qualitycontrol,and
1.3 This standard does not purport to address all of the specification purposes. However, no correlation has been
safety concerns, if any, associated with its use. It is the established between the results of this test method and service
responsibility of the user of this standard to establish appro- performance.
priate safety and health practices and determine the applica-
5. Apparatus
bility of regulatory limitations prior to use.
5.1 Pressure Differential Scanning Calorimeter (PDSC),
2. Terminology
equipped with the following items:
2.1 Definitions of Terms Specific to This Standard: 5.1.1 Sample Enclosure, with capability to 3.5 6 0.2 MPa
2.1.1 extrapolated onset time, n—a time determined on a (500 6 25 psig) at 210°C and pressure gage graduated at
thermal curve, as the intersection of the extrapolated baseline intervals of 200 KPa (28.6 psig) or less.
and a line tangent to the oxidation exotherm constructed at its 5.1.2 Thermal Analyzer.
maximum rate. 5.1.3 Aluminum Solid Fat Index (SFI) Sample Pan—See
2.1.2 oxidation induction time, (OIT), n—a period of time Note 1.
during which the oxidation rate accelerates from zero to a 5.1.4 Oxidation Stability Software.
maximum and which corresponds to the extrapolated onset 5.1.5 Calibration Software.
time. 5.1.6 Calibrated Flowmeter, with a capacity of at least 200
2.1.3 thermal curve, n—a graph of sample heat flow versus mL/min and graduated in intervals of 5 mL or less.
time. 5.1.7 Sample Encapsulation Press.
NOTE 1—It has been found that when oil samples are prepared with SFI
3. Summary of Test Method
pans which have more consistent surface areas than standard flat bottom
3.1 Asmall quantity of oil is weighed into a sample pan and
pans, reproducibility is improved.
placed in a test cell. The cell is heated to a specified
NOTE 2—Stainless steel or copper tubing is compatible with oxygen.
temperature and then pressurized with oxygen. The cell is held NOTE 3—See Fig. 1 for a diagram of a typical test unit.
at a regulated temperature and pressure until an exothermic
6. Reagents and Materials
reaction occurs. The extrapolated onset time is measured and
6.1 Oxygen, a minimum purity of 99.5 % oxygen by vol-
reported as the oxidation induction time for the lubricating oil
ume. (Warning—Oxidizer. Gas under pressure.)
at the specified test temperature.
6.2 Indium, of not less than 99.9 % indium by mass.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.09 on Oxidation. Rhee, In-Sik, “Development of New Oxidation Stability Test Method for
Current edition approved May 10, 2003. Published August 2003. Originally Lubricating Oils Using a Pressure Differential Scanning Calorimeter (PDSC),”
approved in 1997. Last previous edition approved in 1998 as D 6186–98. NLGI Spokesman, Vol 65, No. 3, June 2001, pp. 16–23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6186–98 (2003)
NOTE 4—The melting temperature of indium is 156.6°C at atmospheric
pressure, but has been found to be elevated to 157.4°C under the
conditions of this test method, 3.5 MPa (500 psig) of oxygen.
7.2 Temperature Controller Calibration:
7.2.1 Remove both the sample pan and the reference pan
from the cell, then close the cell. Slowly pressurize the cell
with 3.5 6 0.2 MPa (500 6 25 psig) oxygen and adjust the
purge rate to 100 6 10 mL/min using the cell outlet valve.
Select the desired test temperature (either 210, 180, 155, or
130°C).
7.2.2 Program the cell to maintain the selected test tempera-
ture. If, after 10 min, the displayed cell temperature differs by
more than 6 0.2°C from the selected temperature, slowly
FIG. 1 PDSC Test Unit
adjustthetemperaturecontrolleruntiltheyagree.Aftermaking
an adjustment, wait at least 5 min to make certain that the
7. Calibration
temperature is stable before continuing. If the PDSC equip-
7.1 Sample Temperature Calibration:
ment does not have this function, the control calibration shall
7.1.1 Weigh approximately 10 mg of indium into an alumi-
be followed according to the equipment manufacturer’s rec-
num sample pan, insert a lid and crimp the lid to the pan using
ommendations.
the encapsulation press. Place the crimped pan onto the sample
7.3 Cell Base Pressure Gage Calibration—Conduct the
platform in the pressure cell. Seal an empty pan in the same
calibration using a calibrated pressure transducer or a previ-
manner and place it on the reference platform. Set the cell
ously calibrated gage according to the pressure cell manufac-
cover in place and close the cell.
turer’s instructions.
7.1.2 Open the oxygen cylinder valve slightly and set a
pressureof3.5 60.2MPa(500 625psig)onthecellinletline
8. Procedure
withthepressureregulator.Partiallyopentheinletvalveonthe
8.1 Before starting a test, the control thermocouple calibra-
cell and allow the pressure to slowly build up in the cell. This
tion shall be conducted at the test temperature (either 210, 180,
requires approximately 2 min. Using the outlet valve, adjust
155, or 130°C) according to 7.2.1 and 7.2.2. When the test
and maintain the oxygen purge rate through the flowmeter at
temperature is not known, conduct the calibration at 210°C.
100 6 10 mL/min.
8.2 Weigh 3.0 6 0.2 mg of oil into a new sample pan.
7.1.3 Set the thermal analyzer to heat from ambient tem-
Spread the sample evenly upon the flat portion. Do not spill
perature (approximately 22°C) to 180°C at a programmed rate
any of the sample into the trough portion of the pan. A flat
of 10°C/min. After completion of the run measure the melting
bottom pan can be used if the sample is placed upon a 0.5 cm
temperature of the indium. If the melting temperature differs
diameter circle in the center of the pan.
from 157.4 6 0.2°C (see Note 4) correct the difference by
8.3 Place the uncovered pan containing the sample onto the
using either the hardware or software calibration procedure
platform of the cell according to the PDSC manufacturer’s
described in the manufacturer’s instruction manual. If the
instructions for placing the sample pan. Place a new empty pan
hardware calibration procedure is used, perform the tempera-
of the same configuration onto the cell platform according to
ture co
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