ASTM D6185-97(2002)e1
(Practice)Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases
Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases
SCOPE
1.1 This practice covers a protocol for evaluating the compatibility of one or three binary mixtures of lubricating greases by comparing their properties or performance relative to those of the neat greases comprising the mixture.
1.2 Three properties are evaluated in a primary testing protocol using standard test methods: (1) dropping point by Test Method D 566 (or Test Method D 2265); (2) shear stability by Test Methods D 217, 100 000-stroke worked penetration; and (3) storage stability at elevated-temperature by change in 60-stroke penetration (Test Method D 217). For compatible mixtures (those passing all primary testing), a secondary (nonmandatory) testing scheme is suggested when circumstances indicate the need for additional testing.
1.3 Sequential or concurrent testing is continued until the first failure. If any mixture fails any of the primary tests, the greases are incompatible. If all mixtures pass the three primary tests, the greases are considered compatible.
1.4 This practice applies only to lubricating greases having characteristics suitable for evaluation by the suggested test methods. If the scope of a specific test method limits testing to those greases within a specified range of properties, greases outside that range cannot be tested for compatibility by that test method. An exception to this would be when the tested property of the neat, constituent greases is within the specified range, but the tested property of a mixture is outside the range because of incompatibility.
1.5 This practice does not purport to cover all test methods that could be employed.
1.6 This standard does not purport to address all the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and practices and determine the applicability of regulatory limitations prior to use. For specific safety information, see 7.2.3.
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An American National Standard
e1
Designation:D6185–97 (Reapproved 2002)
Standard Practice for
Evaluating Compatibility of Binary Mixtures of Lubricating
Greases
This standard is issued under the fixed designation D 6185; 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 placed in the text editorially in May 2002.
1. Scope 2. Referenced Documents
1.1 This practice covers a protocol for evaluating the 2.1 ASTM Standards:
compatibility of one or three binary mixtures of lubricating D 217 Test Methods for Cone Penetration of Lubricating
greases by comparing their properties or performance relative Grease
to those of the neat greases comprising the mixture. D 566 Test Method for Dropping Point of Lubricating
1.2 Three properties are evaluated in a primary testing Grease
protocol using standard test methods: (1) dropping point by D 972 Test Method for Evaporation Loss of Lubricating
Test Method D 566 (or Test Method D 2265); (2) shear Greases and Oils
stability by Test Methods D 217, 100 000–stroke worked D 1092 Test Method for Measuring Apparent Viscosity of
penetration;and(3)storagestabilityatelevated-temperatureby Lubricating Greases
change in 60-stroke penetration (Test Method D 217). For D 1263 TestMethodforLeakageTendenciesofAutomotive
compatible mixtures (those passing all primary testing), a Wheel Bearing Greases
secondary (nonmandatory) testing scheme is suggested when D 1264 Test Method for Determining Water Washout Char-
circumstances indicate the need for additional testing. acteristics of Lubricating Greases
1.3 Sequential or concurrent testing is continued until the D 1403 Test Method for Cone Penetration of Lubricating
first failure. If any mixture fails any of the primary tests, the Grease Using One-Quarter and One-Half Scale Cone
greases are incompatible. If all mixtures pass the three primary Equipment
tests, the greases are considered compatible. D 1478 Test Method for Low-Temperature Torque of Ball
1.4 This practice applies only to lubricating greases having Bearing Greases
characteristics suitable for evaluation by the suggested test D 1742 Test Method for Oil Separation from Lubricating
methods. If the scope of a specific test method limits testing to Grease During Storage
those greases within a specified range of properties, greases D 1743 Test Method for Determining Corrosion Preventive
outsidethatrangecannotbetestedforcompatibilitybythattest Properties of Lubricating Greases
method. An exception to this would be when the tested D 1831 Test Method for Roll Stability of Lubricating
property of the neat, constituent greases is within the specified Grease
range, but the tested property of a mixture is outside the range D 2265 Test Method for Dropping Point of Lubricating
because of incompatibility. Grease Over Wide Temperature Range
1.5 This practice does not purport to cover all test methods D 2266 Test Method for Wear Preventive Characteristics of
that could be employed. Lubricating Grease (Four-Ball Method)
1.6 This standard does not purport to address all the safety D 2509 Test Method for Measurement of Load-Carrying
concerns, if any, associated with its use. It is the responsibility Capacity of Lubricating Greases (Timken Method)
of the user of this standard to establish appropriate safety and D 2595 Test Method for Evaporation Loss of Lubricating
practices and determine the applicability of regulatory limita- Greases over WideTemperature Range
tions prior to use. For specific safety information, see 7.2.3. D 2596 Test Method for Measurement of Extreme-Pressure
Properties of Lubricating Grease (Four-Ball Method)
D 3336 Test Method for Life of Lubricating Greases in Ball
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum
Products and Lubricants and is the direct responsibility of Subcommittee D02.G on
Lubricating Grease.
Current edition approved Nov. 10, 1997. Published January 1998. Annual Book of ASTM Standards, Vol 05.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6185–97 (2002)
Bearings at Elevated Temperatures 3.1.6 thickener, n—in a lubricating grease, a substance
D 3337 Test Method for Determining Life and Torque of composed of finely divided particles dispersed in a liquid
Lubricating Greases in Small Ball Bearings lubricant to form the product’s structure.
D 3527 Test Method for Life Performance of Automotive
3.1.6.1 Discussion—The thickener can be fibers (such as
Wheel Bearing Grease
various metallic soaps) or plates or spheres (such as certain
D 4049 Test Method for Determining the Resistance of
non-stop thickeners) which are insoluble or, at most, only very
Lubricating Grease to Water Spray
slightly soluble in the liquid lubricant. The general require-
D 4170 Test Method for Fretting Wear Protection by Lubri- ments are that the solid particles be extremely small, uniformly
cating Grease
dispersed, and capable of forming a relatively stable, gel-like
D 4175 Terminology Relating to Petroleum, Petroleum structure with the liquid lubricant. D 217
Products, and Lubricants
3.2 Definitions of Terms Specific to This Standard:
D 4290 Test Method for Determining the Leakage Tenden-
3.2.1 compatibility, n— of lubricating greases, the charac-
cies of Automotive Wheel Bearing Greases Under Accel-
teristic of lubricating greases to be mixed together without
erated Conditions
significant degradation of properties or performance.
D 4425 Test Method for Oil Separation from Lubricating
3.2.1.1 Discussion—When a mixture of two greases has
Grease by Centrifuging (Koppers Method)
properties or performance significantly inferior to both of the
D 4693 Test Method for Low-Temperature Torque of
neat, constituent greases, then the two greases are incompat-
Grease-Lubricated Wheel Bearings
ible.Ifthepropertiesareinferiortothoseofoneneatgreasebut
D 4950 Classification and Specification for Automotive
not inferior to those of the other, then such is not necessarily
Service Greases
considered an indication of incompatibility. To be considered
D 5706 Test Method for Determining Extreme Pressure
significantly inferior, the property of the mixture would be
PropertiesofLubricatingGreasesUsingaHigh-Frequency
worse than the poorer of the two neat greases by an amount
Linear-Oscillation (SRV) Test Machine
exceeding the repeatability of the test method used to evaluate
D 5707 Test Method for Measuring Friction and Wear
the property (see pass and fail). Incompatibility most often is
Properties of Lubricating Grease Using a High-Frequency,
manifested by a degradation in physical properties rather than
Linear-Oscillation (SRV) Test Machine
in chemical properties, although, occurrence of the latter is not
2.2 Federal Standard:
unknown.
Federal Test Method Standard 791C, Method 3467.1, Stor-
3.2.2 borderline compatibility, n—of lubricating greases,
age Stability of Lubricating Grease
the characteristic of lubricating greases to be mixed together
with only slight degradation of properties or performance.
3. Terminology
3.2.2.1 Discussion—Slight degradation means that the
3.1 Definitions:
propertiesorperformanceofthemixtureispoorerthanthoseof
3.1.1 bleed (bleeding), n— of lubricating greases, the sepa-
the two neat greases but by an amount less than the repeatabil-
ration of a liquid lubricant from a lubricating grease for any
ity of the test method used to evaluate the property. (See
cause.
borderline pass).
3.1.2 lubricant, n—any material interposed between two
3.2.3 primary compatibility tests, n—of lubricating greases,
surfaces that reduces the friction or wear between them.
those test methods employed first to evaluate compatibility
D 4175
3.2.3.1 Discussion—The test methods considered the most
3.1.3 lubricating grease, n—a semifluid to solid product of
significant in the evaluation of grease compatibility, insofar as
a dispersion of a thickener in a liquid lubricant.
they provide the most information with the least expenditure of
3.1.3.1 Discussion—Thedispersionofthethickenerformsa
testing resources, include tests for dropping point, consistency
two-phase system and immobilizes the liquid lubricant by
(usually softening) after shearing conditions, and consistency
surface tension and other physical forces. Other ingredients
change after storage at elevated temperatures.
imparting special properties are often included. D 217
3.2.4 secondary compatibility tests, n—of lubricating
3.1.4 spatulate, v—tomixorblendbyspreadingandfolding
greases, those test methods used to evaluate compatibility
with a flat thin, usually metal, tool.
when the primary compatibility tests are insufficient or incon-
3.1.5 syneresis, n—of lubricating greases, the separation of
clusive.
liquid lubricant from a lubricating grease due to shrinkage or
3.2.4.1 Discussion—Such tests are driven by the critical
rearrangement of the structure.
features of a given application. For example, if the application
3.1.5.1 Discussion—Syneresis is a form of bleeding caused
subjects the grease to water contamination, water washout or
byphysicalorchemicalchangesofthethickness.Separationof
water spray-off tests and, perhaps, corrosion tests would be
free oil or the formation of cracks that occur in lubricating
used for additional evaluation. Secondary compatibility tests
greases during storage in containers is most often due to
are suggested, but not required, by this practice.
syneresis.
3.2.5 pass, n—in compatibility testing of grease mixtures, a
test result that is equal to or better than that of the poorer of the
Annual Book of ASTM Standards, Vol 05.02.
two constituent greases.
Annual Book of ASTM Standards, Vol 05.03.
3.2.6 borderline pass, n— in compatibility testing of grease
Available from Standardization Documents Order Desk, Bldg. 4, Section D,
700 Robbins Ave., Philadelphia, PA 19111–5094, Attn: NPODS. mixtures, a test result that is inferior to that of the poorer of the
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D6185–97 (2002)
two constituent greases by an amount not exceeding the imprudent practice. Grease and equipment manufacturers alike
repeatability of the test method used for the evaluation. recognize such practices will occur despite all warnings to the
3.2.6.1 Discussion—Borderline pass, borderline fail, bor- contrary. Thus, both users and suppliers have a need to know
derline compatible, and borderline incompatible are synony- the compatibility characteristics of the greases in question.
mous terms. 5.2 There are two approaches to evaluating the compatibil-
3.2.7 fail, n—in compatibility testing of grease mixtures, a ity of grease mixtures. One is to determine whether such
test result that is inferior to that of the poorer of the two mixtures meet the same specification requirements as the
constituentgreasesbyanamountexceedingtherepeatabilityof constituent components.This approach is not addressed by this
the test method used for the evaluation. practice. Instead, this practice takes a specification-
3.2.8 50:50 mixture, n—a uniform blend of 50 mass % of independent approach; it describes the evaluation of compat-
each of two component greases. ibility on a relative basis using specific test methods.
3.2.9 10:90 mixture, n—a uniform blend of 10 mass % of 5.2.1 Three test methods are used because fewer are not
one grease with 90 mass % of a second grease. sufficiently definitive. For example, in one study, using
3.2.10 90:10 mixture, n—a uniform blend of 90 mass % of 100 000-stroke worked penetration for evaluation, 62 % of the
one grease with 10 mass % of a second grease. mixtures were judged to be compatible. In a high-temperature
storage stability study, covering a broader spectrum of grease
4. Summary of Practice 6
types, only one-third of the mixtures were compatible. These
4.1 Option 1—A 50:50 mixture of two greases to be studies used different criteria to judge compatibility.
evaluated for compatibility is prepared by spatulating. This
5.2.2 Compatibility cannot be predicted with certainty from
mixture and the two neat, constituent greases are tested using foreknowledge of grease composition. Generally, greases hav-
the primary compatibility tests (dropping point, 100 000-stroke
ing the same or similar thickener types will be compatible.
workedpenetration,and change in 60-stroke penetrationdueto Uncommonly, even greases of the same type, although nor-
high-temperature storage). Depending on the performance of
mally compatible when mixed, can be incompatible because of
the mixture, relative to those of the constituent greases, 10:90
incompatible additive treatments. Thus, compatibility needs to
and 90:10 mixtures may need to be tested in addition. Alter-
be judged on a case-by-case basis.
natively, Option 2 can be used. Instead of testing mixtures in
5.3 Two constituent greases are blended in specific ratios.A
sequential order, 10:90 and 90:10 mixtures are tested at the
50:50mixturesimulatesaratiothatmightbeexperiencedwhen
same time the 50:50 mixture is evaluated. If all mixtures pass
one grease (Grease A) is installed in a bearing containing a
the primary compatibility tests, or if the application requires
previously installed, different grease (Grease B), and no
the evaluation of specific properties, secondary compatibility
attemptismadetoflushoutGreaseBwithGreaseA.The10:90
tests can be employed for further evaluation. Such tests can be
and 90:10 ratios are intended to simulate ratios that might
run concurrently, if desired.
occur when attempts are made to flush out Grease B with
Grease A.
5. Significance and Use
NOTE 1—Some companies evaluate 25:75 and 75:25 ratio mixtures
5.1 The compatibility of greases can be important for users
instead of 10:90 and 90:10 ratio mixtures. But, the latter two ratios, which
of grease-lubricated equipment. It is well known that the
are prescribed by this practice, are considered more representative of the
mixing of two greases can produce a substance markedly
flushing practice described in 5.3.
inferiortoeitherofitsconstituentmaterials.Oneormoreofthe
5.3.1 Incompatibility is most often revealed by the evalua-
following can occur. A mixture of incompatible greases most
tion of 50:50 mixtures. However, in some instances 50:50
often softens, sometimes excessively. Occasionally, it can
mixtures are compatible and more dilute ratios are incompat-
harden.Inextremecases,thethickenerandliquidlubricantwill
ible. (See Appendix X1 and Meade.)
completely separat
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