ASTM D128-98(2008)
(Test Method)Standard Test Methods for Analysis of Lubricating Grease
Standard Test Methods for Analysis of Lubricating Grease
SIGNIFICANCE AND USE
These test methods can be used to identify and estimate the amount of some of the constituents of lubricating greases. These test methods are applicable to many, but not all, greases.
Composition should not be considered as having any direct bearing on service performance unless such correlation is established.
Note 2—Details on other test methods for grease analysis can be found in other reference material. , ,
SCOPE
1.1 These test methods for analysis cover greases of the conventional type, which consist essentially of petroleum oil and soap. The constituents that can be determined are soap, unsaponifiable matter (petroleum oil, and so forth), water, free alkalinity, free fatty acid, fat, glycerin, and insolubles.
Note 1—Any of the test methods described herein are best used by an experienced grease analyst who may also be able to make appropriate adaptations of the techniques as occasion requires.
1.2 A supplementary test method is provided in Appendix X1. This test method is intended primarily for application to greases containing thickeners that are essentially insoluble in n-hexane, and to greases that cannot be analyzed by conventional methods because of the presence of such constituents as nonpetroleum fluids or nonsoap-type thickeners, or both. In some cases, these constituents can react with strong acid or alkaline solutions.
1.3 These test methods appear in the following order:
Sections Ash Determination 7-11 Insolubles, Soap, Fat, Petroleum Oil,
and Unsaponifiable Matter12-20 Free Alkali and Free Acid21-23 Water24 Glycerin (Quantitative)25-29
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D128 − 98(Reapproved 2008)
Standard Test Methods for
Analysis of Lubricating Grease
This standard is issued under the fixed designation D128; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 2. Referenced Documents
1.1 These test methods for analysis cover greases of the 2.1 ASTM Standards:
conventional type, which consist essentially of petroleum oil D95 Test Method for Water in Petroleum Products and
and soap. The constituents that can be determined are soap, Bituminous Materials by Distillation
unsaponifiable matter (petroleum oil, and so forth), water, free D156 Test Method for Saybolt Color of Petroleum Products
alkalinity, free fatty acid, fat, glycerin, and insolubles. (Saybolt Chromometer Method)
D217 Test Methods for Cone Penetration of Lubricating
NOTE 1—Any of the test methods described herein are best used by an
Grease
experienced grease analyst who may also be able to make appropriate
D445 Test Method for Kinematic Viscosity of Transparent
adaptations of the techniques as occasion requires.
and Opaque Liquids (and Calculation of Dynamic Viscos-
1.2 A supplementary test method is provided in Appendix
ity)
X1. This test method is intended primarily for application to
D473 Test Method for Sediment in Crude Oils and Fuel Oils
greases containing thickeners that are essentially insoluble in
by the Extraction Method
n-hexane, and to greases that cannot be analyzed by conven-
D804 Terminology Relating to Pine Chemicals, Including
tional methods because of the presence of such constituents as
Tall Oil and Related Products
nonpetroleum fluids or nonsoap-type thickeners, or both. In
D1078 Test Method for Distillation Range of Volatile Or-
some cases, these constituents can react with strong acid or
ganic Liquids
alkaline solutions.
D1193 Specification for Reagent Water
1.3 These test methods appear in the following order:
D1353 Test Method for Nonvolatile Matter in Volatile Sol-
Sections
vents for Use in Paint, Varnish, Lacquer, and Related
Ash Determination 7–11
Products
Insolubles, Soap, Fat, Petroleum Oil, 12–20
and Unsaponifiable Matter
3. Terminology
Free Alkali and Free Acid 21–23
Water 24
3.1 Definitions:
Glycerin (Quantitative) 25–29
3.1.1 asphalt, n—a dark brown-to-black cementitious mate-
1.4 The values stated in SI units are to be regarded as
rial in which the predominating constituents are bitumens.
standard. No other units of measurement are included in this
3.1.1.1 Discussion—Asphalt can be a natural product or a
standard.
material obtained from petroleum processing.
1.5 This standard does not purport to address all of the
3.1.2 candle pitch, n—a dark brown-to-black, tarry or solid,
safety concerns, if any, associated with its use. It is the
by-product residue from soap and candle stock manufacture,
responsibility of the user of this standard to establish appro-
refiningofvegetableoils,refiningofwoolgrease,orrefiningof
priate safety and health practices, and determine the applica-
refuse animal fats.
bility of regulatory limitations prior to use.
3.1.3 cup grease, n—any lubricating grease having physical
properties, such as consistency and texture, suitable for its use
in spring-loaded or screw-type lubricating cups.
These test methods are under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and are the direct responsibility of Subcommit-
tee D02.G0.01 on Chemical and General Laboratory Tests. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
CurrenteditionapprovedMay1,2008.PublishedJuly2008.Originallyapproved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ε1
in 1922. Last previous edition approved in 2003 as D128–98(2003) . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D0128-98R08. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D128 − 98 (2008)
3.1.3.1 Discussion—Cup greases are predominantly NLGI expressed as equivalent milligrams of potassium hydroxide per
No. 3 or 4 calcium greases, but grease types other than calcium gram of sample. D804
are also used.
3.1.12 NLGI, n—National Lubricating Grease Institute.
3.1.4 degras(woolfat,woolgrease,woolwax),n—afat-like
3.1.13 NLGI number, n—a numerical scale for classifying
material comprised primarily of sterols, other higher alcohols,
the consistency range of lubricating greases and based on the
and fatty acids, obtained from the solvent extraction of sheep’s
Test Methods D217 worked penetration.
wool.
NLGI Lubricating Grease Guide
3.1.5 free alkali, n— in lubricating grease, unreacted basic
3.1.14 non-soap thickener (synthetic thickener, inorganic
(alkaline) material present in the product.
thickener, organic thickener), n—in lubricating grease, any of
3.1.5.1 Discussion—Many greases are made with a slight
several specially treated or synthetic materials, excepting
excess of alkali to ensure complete saponification. Free alkali
metallicsoaps,thatcanbethermallyormechanicallydispersed
is determined by acidification of a solvent-thinned specimen
in liquid lubricants to form the lubricating grease structure.
and back titration with standardized, alcoholic potassium
NLGI Lubricating Grease Guide
hydroxide. It is expressed in terms of the predominating alkali
3.1.15 residuum, n—a liquid or semi-liquid product ob-
and a mass % of the total grease composition (for example,
tained as residue from the distillation of petroleum and
mass % lithium hydroxide).
consisting primarily of asphaltic hydrocarbons.
3.1.6 free fatty acid, n—in lubricating grease, unreacted
3.1.15.1 Discussion—Also known as asphaltic oil, asphal-
carboxylic acid(s) present in the product.
tum oil, liquid asphalt, black oil, petroleum tailings, and
3.1.6.1 Discussion—Some greases are made with a slight
residual oil.
excess of carboxylic acid to ensure a non-alkaline product.
Free fatty acid is determined by neutralization of a solvent-
3.1.16 rosin oil, n—a viscous, oily liquid obtained as a
thinned specimen with standardized, alcoholic potassium hy-
condensate when the residue (rosin) from turpentine produc-
droxide.Regardlessoftheactualcompositionofthecarboxylic
tion is subjected to dry, destructive distillation.
acid(s), it is expressed as free oleic acid and as a mass % of the
3.1.16.1 Discussion—Also used to describe specially com-
total grease composition.
pounded oils having a rosin base.
3.1.7 insolubles, n—in lubricating greases analysis, the
3.1.17 saponification, n—the interaction of fats, fatty acids,
material remaining after the acid hydrolysis, water extraction,
or esters generally with an alkali to form the metallic salt,
and solvent extraction of soap-thickened greases.
which is commonly called soap.
3.1.7.1 Discussion—Consisting of such products as
3.1.17.1 Discussion—Soap thickeners are most often made
graphite, molybdenum disulfide, insoluble polymers, and so
by in situ saponification in the lubricating grease base oil.
forth.
However, the use of pre-formed soaps is also common;
3.1.8 lubricating grease, n—a semi-fluid to solid product of
dispersion is effected by mechanical means and usually with
a dispersion of a thickener in a liquid lubricant.
heat. NLGI Lubricating Grease Guide
3.1.8.1 Discussion—The qualifying term, lubricating,
3.1.18 single base, adj— in lubricating grease, relating to a
should always be used. The term, grease, used without the
thickener comprised of soaps of only one metal.
qualifier refers to a different product, namely certain natural or
3.1.19 soap, n—in lubricating grease, a product formed in
processed animal fats, such as tallow, lard, and so forth.
the saponification (neutralization) of fats, fatty acids, or esters
3.1.9 mixed base, adj—in lubricating grease, the description
by inorganic bases.
of a thickener system composed of soaps of two metals.
3.1.20 Soxhlet apparatus, n—a device, usually of glass,
3.1.9.1 Discussion—Although mixed-base grease can be
used to extract soluble material from a mixture of soluble and
made with soaps of more than two metals, in practice, such is
insoluble (generally solid) materials, by passing a volatile
rarely, if ever, encountered. All of the soaps need not be
solvent through the sample and recirculating the solvent by
thickeners, although the major soap constituent will be one
refluxing.
capable of forming a lubricating grease structure. Because the
mixed soaps are seldom present in equal amounts. The pre-
3.1.21 tar, n—a brown or black, bituminous, liquid or
dominant soap is referred to first.
semi-solid comprised primarily of bitumens condensed in the
NLGI Lubricating Grease Guide
processingofcoal,petroleum,oil-shale,wood,orotherorganic
materials.
3.1.10 montan wax, n—a wax-like material comprised pri-
marily of montanic acid and its ester, higher aliphatic alcohols,
3.1.22 thickener, n—in lubricating grease, a substance com-
and resins obtained from the solvent extraction of lignite.
posed of finely divided solid particles dispersed in a liquid
3.1.11 neutralization number, n—of petroleum oil, the quan- lubricant to form the product’s structure.
tity of acid or base required to titrate to neutrality and
3.1.22.1 Discussion—The thickener can be fibers (such as
various metallic soaps) or plates or spheres (such as certain
non-soapthickeners),whichareinsolubleor,atmost,onlyvery
slightly soluble in the liquid lubricant. The general require-
Available from National Lubricating Grease Institute, 4635 Wyandotte St.,
Kansas City, MO 64112-1596. ments are that the solid particles be extremely small, uniformly
D128 − 98 (2008)
TABLE 1 Physical Requirements of n-hexane
dispersed, and capable of forming a relatively stable, gel-like
structure with the liquid lubricant. D217 Test Requirement ASTM
A
Designation
3.1.23 thimble, n—in Soxhlet apparatus, a closed-end po-
Initial boiling point, min, °C 66.1 D1078
rous cylinder used to hold the material to be extracted, usually
Dry point, max, °C 68.9 D1078
made of thick matted filter paper but sometimes made of Nonvolatile matter, max, g/100 mL 0.001 D1353
Color, Saybolt, min + 30 D156
ceramic.
A
Reaction with alkalies .
3.1.24 total fluid constituent, n—in lubricating grease
A
Boil 125 mL of n-hexane with 10 mL of 0.5 N alcoholic KOH solution and 50 mL
analysis, the n-hexane-soluble material extracted from the of neutral 50 % alcohol for 1 ⁄2 h on a hot plate. Use a glass tube about 7 mm in
inside diameter and 750 mm in length as a reflux condenser. After cooling, titrate
lubricating grease sample.
the solutions with 0.5 N HCl using phenolphthalein as the indicator. Not less than
3.1.24.1 Discussion—Typical materials include petroleum
9.8mL of0.5 N HCl shall be required for neutralization. The amount of alkali
oil, non-petroleum fluid, soluble fats, and soluble additives. consumed in this test shall be deducted as a blank correction in the fat
determination on Solution E.
3.1.25 total n-hexane-insoluble material, n—in lubricating
grease analysis, that portion of grease (excluding free alkali)
that is essentially insoluble in n-hexane.
3.1.25.1 Discussion—Typical materials include thickeners,
fillers, inorganic salts, asphaltenes, or any combinations of
5.3 Acetone—American Chemical Society Reagent Grade
these(alsoincludesinsolublematerialsfoundintheanalysisof
Acetone.(Warning—Extremelyflammable.Vaporsmaycause
contaminated grease). Free alkali content is generally insignifi-
flash fires.)
cant.
5.4 Alcohol (50 %)—The alcohol shall be prepared from
8,9
3.1.26 unsaponifiable matter, n—in lubricating grease, or-
commercial 95 % ethanol or denatured alcohol (Warning—
ganic materials, either added or found with fatty materials,
Flammable.Denatured.Cannotbemadenontoxic)bydistilling
which do not react during saponification.
fromNaOHandneutralizingexactlywithNaOHorKOHusing
phenolphthalein as the indicator. (Warning —In addition to
4. Significance and Use
other precautions, avoid skin contact or ingestion.) Dilute with
4.1 These test methods can be used to identify and estimate
an equal volume of water.
the amount of some of the constituents of lubricating greases.
5.5 Ammonium Carbonate—(NH ) CO.(Warning—
4 2 3
These test methods are applicable to many, but not all, greases.
Harmful if swallowed.) (Warning—Harmful if swallowed.)
4.2 Composition should not be considered as having any
5.6 Butter Yellow Indicator (0.02 g/mL)—Toluene solution
direct bearing on service performance unless such correlation
(Warning—Flammable. Vapor harmful) of
is established.
p-dimethylaminoazobenzene. (Warning—Suspected carcino-
NOTE 2—Details on other test methods for grease analysis can be found
gen. In addition to other precautions, avoid inhalation or skin
4,5,6
in other reference material.
contact.)
5. Reagents 5.7 t-ButylAlcohol,meltingpoint24to25.5°C(Warning—
Flammable liquid; causes eye burns).
5.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that 5.8 Carbon Disulfide (CS ). (Warning—Extremely flam-
mable. Poison. Vapor may cause flash fire. Vapor harmful.
all reagents shall conform to the specifications of the Commit-
tee onAnalytical Reagents of theAmerican Chemical Society, Capable of self-ignition at 100°C or above. Harmful or fatal if
swallowed. May be absorbed through the skin.)
where such specifications are available. Other grades may be
used, provided it is first ascertained that the reagent is of
5.9 EthylEther.(Warning—Extremelyflammable.Harmful
sufficiently high purity to permit its use without lessening the
if inhaled. May cause eye injury. Effects may be delayed. May
accuracy of the determination.
form explosive peroxides. Vapors may cause flash fire. Mod-
erately toxic. Irritating to skin.)
5.2 Purity of Water—Unless otherwise indicated, references
towatershallbeunderstoodtomeanreagentwaterconforming 9,10
5.10 n-hexane, high-purity grade, conforming to the
to Specification D1193, Type III.
requirements of Table 1.(Warning—Extremely flammable.
Harmful if inhaled. May produce nerve cell damage. Vapors
may cause flash fire.)
Stanton, G. M., “Examination of Grease by Infrared Spectroscopy,” NLGI
Spokesman, Vol 38, No. 5, August 1974, pp. 153–165.
Stanton, G. M., “Grease Analysis, a Modern Multitechnique Approach,”
Preprint NLGI Annual Meeting, Oct 26–29, 1975.
6 8
Bonomo, F. S., and Schmidt, J.
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