ASTM D6595-00

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An American National Standard
Designation:D6595–00
Standard Test Method for
Determination of Wear Metals and Contaminants in Used
Lubricating Oils or Used Hydraulic Fluids by Rotating Disc
Electrode Atomic Emission Spectrometry
This standard is issued under the fixed designation D 6595; 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.
1. Scope 3.1.2 calibration, n—the determination of the values of the
significant parameters by comparison with values indicated by
1.1 This test method covers the determination of wear
a set of reference standards.
metals and contaminants in used lubricating oils and used
3.1.3 calibration curve, n—the graphical or mathematical
hydraulic fluids by rotating disc electrode atomic emission
representation of a relationship between the assigned (known)
spectroscopy (RDE-AES).
values of standards and the measured responses from the
1.2 This test method provides a quick indication for abnor-
measurement system.
mal wear and the presence of contamination in new or used
3.1.4 calibration standard, n—a standard having an ac-
lubricants and hydraulic fluids.
cepted value (reference value) for use in calibrating a measure-
1.3 This test method uses oil-soluble metals for calibration
ment instrument or system.
and does not purport to relate quantitatively the values deter-
3.1.5 emission spectroscopy, n—measurement of energy
mined as insoluble particles to the dissolved metals.Analytical
spectrum emitted by or from an object under some form of
results are particle size dependent and low results may be
energetic stimulation; for example, light, electrical discharge,
obtainedforthoseelementspresentinusedoilsamplesaslarge
and so forth.
particles.
3.2 Definitions of Terms Specific to This Standard:
1.4 The test method is capable of detecting and quantifying
3.2.1 arc discharge, n—a self-sustaining, high current den-
elements resulting from wear and contamination ranging from
sity, high temperature discharge, uniquely characterized by a
dissolved materials to particles approximately 10 µm in size.
cathode fall nearly equal to the ionization potential of the gas
1.5 The values stated in SI units are to be regarded as the
or vapor in which it exists.
standard. The values given in parentheses are for information
3.2.2 check sample, n—a reference material usually pre-
only. The preferred units are mg/kg (ppm by mass).
pared by a laboratory for its own use as a calibration standard,
1.6 This standard does not purport to address all the safety
as a measurement control standard, or for the qualification of a
problems, if any, associated with its use. It is the responsibility
measurement method.
of the user of this method to establish appropriate safety and
3.2.3 contaminant, n—material in an oil sample that may
health practices and determine the applicability of regulatory
cause abnormal wear or lubricant degradation.
limitations prior to use.
3.2.4 counterelectrode,n—eitheroftwographiteelectrodes
2. Referenced Documents in an atomic emission spectrometer across which an arc or
spark is generated.
2.1 ASTM Standards:
3.2.5 graphite disc electrode, n—a soft form of the element
D 4057 Practice for Manual Sampling of Petroleum and
carbon manufactured into the shape of a disc for use as a
Petroleum Products
counter electrode in arc/spark spectrometers for oil analysis.
3. Terminology
3.2.6 graphite rod electrode, n—a soft form of the element
carbon manufactured into the shape of a rod for use as a
3.1 Definitions:
counter electrode in arc/spark spectrometers for oil analysis.
3.1.1 burn, vt—in emission spectroscopy, to vaporize and
3.2.7 profiling, n—to set the actual position of the entrance
excite a specimen with sufficient energy to generate spectral
slit to produce optimum measurement intensity.
radiation.
3.2.8 standardization, n—the process of reestablishing and
correcting a calibration curve through the analysis of at least
This test method is under the jurisdiction of ASTM Committee D02 on
two known oil standards.
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
3.2.9 uptake rate, n—the amount of oil sample that is
D02.03 on Elemental Analysis.
physically carried by the rotating disc electrode into the arc for
Current edition approvedNov. 10, 2000. Published November 2000.
Annual Book of ASTM Standards, Volume 05.02. analysis.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6595–00
3.2.10 wear metal, n—material resulting from damage to a 7. Apparatus
solid surface due to relative motion between that surface and a
7.1 Electrode Sharpener—An electrode sharpener is neces-
contacting substance or substances.
sary to remove the contaminated portion of the rod electrode
remainingfromthepreviousdetermination.Italsoformsanew
4. Summary of Test Method
160° angle on the end of the electrode. Electrode sharpeners
4.1 Wear metals and contaminants in a used oil test speci- are not required for instruments using a pre-shaped disc
men are evaporated and excited by a controlled arc discharge electrode as the counter electrode.
using the rotating disk technique. The radiant energies of 7.2 Rotating Disc Electrode Atomic Emission Spectrometer,
selected analytical lines and one or more references are a simultaneous spectrometer consisting of excitation source,
collected and stored by way of photomultiplier tubes, charge polychromator optics, and a readout system. Suggested ele-
coupled devices or other suitable detectors. A comparison is ments and wavelengths are listed in Table 1. When multiple
made of the emitted intensities of the elements in the used oil wavelengths are listed, they are in the order of preference or
test specimen against those measured with calibration stan- desired analytical range.
dards.The concentrations of the elements present in the oil test 7.3 Heated Ultrasonic Bath (Recommended), an ultrasonic
specimen are calculated and displayed. They may also be bathtoheatandhomogenizeusedoilsamplestobringparticles
into homogeneous suspension. The ultrasonic bath shall be
entered into a data base for processing.
used on samples containing large amount of debris and those
that have been in transit or stored for 48 hours or longer.
5. Significance and Use
5.1 Used Lubricating Oil—The determination of debris in
8. Reagents and Materials
used oil is a key diagnostic method practiced in machine
condition monitoring programs. The presence or increase in 8.1 Base Oil, a 75 cSt base oil free of analyte to be used as
concentration of specific wear metals can be indicative of the a calibration blank or for blending calibration standards.
early stages of wear if there are baseline concentration data for 8.2 Check Samples, An oil standard or sample of known
comparison.Amarkedincreaseincontaminantelementscanbe concentration which is periodically analyzed as a go/no go
indicative of foreign materials in the lubricants, such as sample to confirm the need for standardization based on an
antifreeze or sand, which may lead to wear or lubricant allowable6 10 % accuracy limit.
degradation. The test method identifies the metals and their 8.3 Cleaning Solution, An environmentally safe, non-
concentration so that trends relative to time or distance can be chlorinated,rapidevaporating,andnon-filmproducingsolvent,
established and corrective action can be taken prior to more to remove spilled or splashed oil sample in the sample stand.
8.4 Disc Electrode, a graphite disc electrode of high-purity
serious or catastrophic failure.
graphite (spectroscopic grade). Dimensions of the electrodes
shall conform to those shown in Fig. 1.
6. Interferences
8.5 Glass Cleaning Solution, capable of cleaning and re-
6.1 Spectral—Mostspectralinterferencescanbeavoidedby
moving splashed oil sample from the quartz window that
judicious choice of spectral lines. High concentrations of
protects the entrance lens and fiber optic. Isopropyl rubbing
additive elements can have an interfering influence on the
alcohol or ammonia based window cleaner has been found to
spectral lines used for determining wear metals. Instrument
be suitable for this purpose.
manufacturers usually compensate for spectral interferences
8.6 Organometallic Standards, single or multi-element
during factory calibration. A background correction system,
blended standards for use as the high concentration standard
which subtracts unwanted intensities on either side of the
for instrument standardization purposes or for use as a check
spectral line, shall also be used for this purpose. When spectral
sample to confirm calibration. Typical concentrations in the
interferencescannotbeavoidedwithspectrallineselectionand
upper calibration point standard for used oil applications is 100
backgroundcorrection,thenecessarycorrectionsshallbemade
mg/kg for wear metals and contaminants, and 900 mg/kg for
using the computer software supplied by the instrument manu-
additive elements.
facturer.
6.2 Viscosity Effects—Differences in viscosity of used oil
samples will cause differences in uptake rates. Internal refer-
TABLE 1 Elements and Recommended Wavelengths
ences of the instrument will compensate for a portion of the
Element Wavelength, nm Element Wavelength, nm
differences. In used oil applications, the hydrogen 486.10 nm
spectral line has become the industry standard for use as an Aluminum 308.21 Nickel 341.48
Barium 230.48, 455.40 Phosphorus 255.32, 214.91
internalreference.Withoutareference,trendeddataonusedoil
Boron 249.67 Potassium 766.49
will be adversely affected if the sample base stock has a
Calcium 393.37, 445.48 Silicon 251.60
different viscosity from the base line samples. Chromium 425.43 Silver 328.07, 243.78
Copper 324.75, 224.26 Sodium 588.89, 589.59
6.3 Particulate—When large particles over 10 µm in size
Iron 259.94 Tin 317.51
are detected, the analytical results will be lower than the actual
Lead 283.31 Titanium 334.94
concentration they represent. Large particles may not be Lithium 670.78 Tungsten 400.87
Manganese 403.07, 294.92 Vanadium 290.88, 437.92
effectively transported by the rotating disk electrode sample
Magnesium 280.20, 518.36 Zinc 213.86
introduction system into the arc, nor will they be fully
Molybdenum 281.60
vaporized by the spark.
D6595–00
and prior to pouring a test specimen for analysis. The bath
temperature shall be at least 60°C and the total agitation time
at least 2 min.
10.3 SpecimenHolders—Usedoilsamplesandoilstandards
shallbepouredintoaspecimenholderofatleast1mLcapacity
prior to analysis. Exercise care to pour the sample consistently
NOTE—All dimensions are in millimetres; material is high-purity
to the same level in the specimen holders to maintain good
graphite (spectroscopic grade).
repeatability of analysis.
FIG. 1 Graphite Disc Electrode
10.4 Specimen Table—The specimen table shall be adjusted
so that when it is in the fully raised position, at least one-third
8.6.1 Standards have a shelf-life and shall not be used to
of the disc electrode is immersed in the oil test specimen.
standardize an instrument if they have exceeded the expiration
date.
11. Preparation of Apparatus
8.7 Counter Electrode—The counter electrode can be either
11.1 Warm-up Burns—If the instrument has been idle for
a rod or a disc. The counter electrode must be high-purity
several hours, it may be necessary to conduct at least three
graphite (spectroscopic grade). Dimensions of the counter
warm-up burns to stabilize the excitation source. The warm-up
electrodes shall conform to those shown in Fig. 2.
procedure can be performed with any oil sample or standard.
8.8 Specimen Holders—A variety of specimen holders can
Consult the manufacturer’s instructions for specific warm-up
be used for the analysis of used oil samples. Disposable
requirements.
specimen holders must be discarded after each analysis and
11.2 Optical Profile—Perform the normal optical profile
reusable specimen holders must be cleaned after each analysis.
procedure called for in the operation manual of the instrument.
All specimen holders must be free of contamination and shall
An optical profile shall also be performed if the instrument has
be stored accordingly. Specimen holder and covers shall be
been inoperative for an extended period of time or if the
used on hydraulic oil samples that may catch on fire during the
temperature has shifted more than 10°C since the last calibra-
analysis.
tion check.
11.3 Validation Check—A go/no go standardization check
9. Sampling
can be performed with one or more check samples to confirm
9.1 The used oil sample taken for the analysis must be
calibration prior to the analysis of routine samples. A calibra-
representative of the entire system. Good sampling procedures
tion standard or known oil sample can be used for this purpose.
are key to good analyses and samples must be taken in
The optical profile and standardization routine recommended
accordance with Practice D 4057.
by the instrument manufacturer shall be performed if the
validation check fails to meet the6 10 % accuracy guidelines
10. Preparation of Test Specimen
for each element of interest.
10.1 Homogenization—Used oil samples may contain par-
ticulate matter and, in order to be representative, must always
12. Calibration
be vigorously shaken prior to pouring a test specimen for
analysis. 12.1 Factory Calibration—The analytical range for each
10.2 Ultrasonic Homogenization—Samples that have been element is established through the analysis of organometallic
in transit for several days, idle in storage or very viscous, shall
standardsatknownconcentrations.Acalibrationcurveforeach
be placed in a heated ultrasonic bath to break up clusters of element is established and correction factors are set to produce
particles and to bring them back into suspension. The samples a linear response. Analyses of test specimens must be per-
shall be vigorously shaken after being in the ultrasonic bath formed within the linear range of response. The typical
NOTE—All dimensions are in millimetres; material is high-purity graphite (spectroscopic grade).
FIG. 2 Graphite Counter Electrode
D6595–00
TABLE 2 Repeatability TABLE 4 Reproducibility
Element Range, mg/kg Repeatability, mg/kg Element Range, mg/kg Reproducibility, mg/kg
0.45 0.45
Aluminum 0.23–101 0.5419(X+0.57) Aluminum 0.25–100 1.457(X+0.57)
1.18 .18
Barium 28–115 0.0694X Barium 28–115 0.1317X
0.56 0.56
Boron 0.14–120
...