ASTM D1474/D1474M-13(2023)
(Test Method)Standard Test Methods for Indentation Hardness of Organic Coatings
Standard Test Methods for Indentation Hardness of Organic Coatings
SIGNIFICANCE AND USE
4.1 Indentation hardness measurements have proven to be useful in rating coatings on rigid substrates for their resistance to mechanical abuse, such as that produced by blows, gouging, and scratching. These measurements do not necessarily characterize the resistance to mechanical abuse of coatings that are required to remain intact when deformed.
SCOPE
1.1 These test methods cover the determination of the indentation hardness of organic materials such as dried paint, varnish, and lacquer coatings, when applied to an acceptable plane rigid surface, for example, metal or glass.
1.2 Two methods are covered as follows:
Sections
Method A—Knoop Indentation Hardness
6 – 12
Method B—Pfund Indentation Hardness
13 – 19
1.3 Method A, which has the greater precision, provides hardness values in terms of Knoop Hardness Number (KHN). Method B provides hardness in terms of Pfund Hardness Number (PHN). Although the hardness value scales of these methods differ, the methods agree in the ranking of coating hardness.
1.4 Test Method A of these test methods is similar in content (but not technically equivalent) to ISO 6441-1 and ISO 6441-2.
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.
1.6 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D1474/D1474M − 13 (Reapproved 2023)
Standard Test Methods for
Indentation Hardness of Organic Coatings
This standard is issued under the fixed designation D1474/D1474M; 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 cover the determination of the 2.1 ASTM Standards:
indentation hardness of organic materials such as dried paint, D823 Practices for Producing Films of Uniform Thickness
varnish, and lacquer coatings, when applied to an acceptable of Paint, Coatings and Related Products on Test Panels
plane rigid surface, for example, metal or glass. D1005 Test Method for Measurement of Dry-Film Thick-
ness of Organic Coatings Using Micrometers
1.2 Two methods are covered as follows:
D7091 Practice for Nondestructive Measurement of Dry
Sections
Film Thickness of Nonmagnetic Coatings Applied to
Method A—Knoop Indentation Hardness 6 – 12
Method B—Pfund Indentation Hardness 13 – 19 Ferrous Metals and Nonmagnetic, Nonconductive Coat-
ings Applied to Non-Ferrous Metals
1.3 Method A, which has the greater precision, provides
E384 Test Method for Microindentation Hardness of Mate-
hardness values in terms of Knoop Hardness Number (KHN).
rials
Method B provides hardness in terms of Pfund Hardness
2.2 Other Standards:
Number (PHN). Although the hardness value scales of these
ISO 6441-1 Paints and Varnishes—Determination of micro-
methods differ, the methods agree in the ranking of coating
indentation hardness—Part 1: Knoop hardness by mea-
hardness.
surement of the indentation length
1.4 Test Method A of these test methods is similar in content
ISO 6441-2 Paints and Varnishes—Determination of micro-
(but not technically equivalent) to ISO 6441-1 and ISO 6441-2.
indentation hardness—Part 2: Knoop hardness by mea-
1.5 The values stated in either SI units or inch-pound units
surement of the indentation depth under load
are to be regarded separately as standard. The values stated in
3. Terminology
each system are not necessarily exact equivalents; therefore, to
ensure conformance with the standard, each system shall be
3.1 Definitions:
used independently of the other, and values from the two
3.1.1 indentation hardness, n—the resistance to penetration
systems shall not be combined.
by an indenter.
1.6 This standard does not purport to address the safety
3.1.2 Knoop indenter, n—a pyramidal diamond of pre-
concerns, if any, associated with its use. It is the responsibility
scribed dimensions.
of the user of this standard to establish appropriate safety,
3.1.3 Pfund indenter, n—hemispherical quartz or sapphire
health, and environmental practices and determine the appli-
indenter of prescribed dimensions.
cability of regulatory limitations prior to use.
3.1.4 Knoop hardness number, KHN, n—the indentation
1.7 This international standard was developed in accor-
hardness determined with a Knoop indenter, and calculated as
dance with internationally recognized principles on standard-
follows:
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
KHN 5 L/A 5 L/l C (1)
p p
mendations issued by the World Trade Organization Technical
where:
Barriers to Trade (TBT) Committee.
L = load applied to the indenter, kg,
These test methods are under the jurisdiction of ASTM Committee D01 on
Paint and Related Coatings, Materials, and Applications and are the direct For referenced ASTM standards, visit the ASTM website, www.astm.org, or
responsibility of Subcommittee D01.23 on Physical Properties of Applied Paint contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Films. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2023. Published February 2023. Originally the ASTM website.
approved in 1957. Last previous edition approved in 2018 as D1474/D1474M – 13 Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
(2018). DOI: 10.1520/D1474_D1474M-13R23. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1474/D1474M − 13 (2023)
indenter into contact with the test surface with negligible
l = measured length of long diagonal of the indentation,
impact, apply the selected full load, maintain it for 18 s 6
mm,
0.5 s, and withdraw the indenter.
C = indenter constant relating l to A , and
p p
A = projected area of indentation, mm .
p
7.2 Knoop Indenter—The Knoop indenter is a pyramidal
3.1.5 Pfund hardness number, PHN, n—the indentation diamond with included longitudinal angles of 172° 30' and
hardness determined with a Pfund indenter, and calculated as
included transverse angle of 130° 0'.
follows:
NOTE 1—The ratio of the long to the short diagonal of the impression
2 2
PHN 5 L/A 5 4L/πd 5 1.27 L/d (2) is approximately 7:1; the ratio of the long diagonal to the depth of
~ !
penetration is approximately 30:1.
where:
7.3 Microscope—The microscope shall have a filar microm-
L = load/kg applied to the indenter, kg,
eter eyepiece and sufficient objectives to permit the measure-
A = area of projected indentation, mm , and
ment of the length of impression to within 61 %. The
d = diameter of projected indentation, mm.
specimen shall be firmly supported on a movable micrometer
stage attached to the microscope.
4. Significance and Use
4.1 Indentation hardness measurements have proven to be
8. Calibration
useful in rating coatings on rigid substrates for their resistance
8.1 Adjust the illumination in the microscope to give
to mechanical abuse, such as that produced by blows, gouging,
maximum contrast when viewing an indentation.
and scratching. These measurements do not necessarily char-
8.2 By means of a calibrated scale, determine the factor for
acterize the resistance to mechanical abuse of coatings that are
each microscope objective that converts the filar scale units of
required to remain intact when deformed.
the eyepiece to millimetres.
5. Test Specimens
8.3 With a 25 g load on the indenter, determine the KHN of
5.1 The substrate for the coating shall be an acceptable
a calibrated standard (Note 2) with an assigned value not
plane rigid surface such as glass or metal.
greater than 50 KHN. If the obtained value is within 65 % of
the assigned value, the instrument is considered to be in
5.2 The coating thickness on any one panel shall be uniform
calibration.
within 3 μm [0.1 mil]. Coatings to be compared shall be of
equal thickness within 5 μm [0.2 mil]. For maximum accuracy,
NOTE 2—A suitable source of standard reference materials in this
the minimum permissible coating thickness shall be such that
hardness range is available from the U.S. National Institute for Standards
and Technology. By agreement of the parties concerned, a stable
the depth of indentation does not exceed three fourths of the
specimen (such as an aged coating or a baked enamel applied to a flat
coating thickness, to minimize the effect of the substrate.
substrate) could be used to calibrate the participating hardness testers.
5.3 At least three replicate specimens shall be tested for
each coating to be evaluated. 9. Procedure
9.1 Unless otherwise specified, make the hardness determi-
5.4 Coatings should be applied in accordance with Practices
D823 and their dry film thickness should be measured in nations at 23 °C 6 2 °C [73.5 °F 6 3.50 °F] and 50 % 6 5 %
relative humidity after equilibrating the specimens under these
accordance with Test Methods D1005 or D7091.
conditions for at least 24 hours.
5.5 From precoated sheets cut at least three specimens. Use
9.2 Rigidly attach the specimen to the movable stage so that
only plane (flat) sheets and round the edges slightly. The
coating shall be free of oil and other foreign matter. Measure the surface to be measured is normal to the direction of
indentation. Mount the panel so that is cannot move with
the film thickness as in 5.4.
respect to the stage in any direction during the test.
METHOD A—KNOOP INDENTATION HARDNESS
9.3 Use the microscope to select an area of the test specimen
that is free of surface irregularities and imperfections. Place
6. Summary of Method
this area under the indenter by means of the movable microm-
6.1 This method consists of applying a load to the surface of
eter stage.
a coating by means of a pyramidal shaped diamond having
NOTE 3—If good impressions cannot be obtained because of the
specified face angles, and converting the measurements of the
roughness of the surface of the specimen, gently polish the surface with
resultant permanent impression to a hardness number.
No. 400 carborundum and finish off with jewelers rouge before making the
impression.
7. Apparatus
9.4 Present the apparatus to apply a load that permits the
7.1 Hardness Tester , consisting of a load applicator, a
length of identification to be read accurately but does not cause
Knoop indenter, and a microscope fitted with a movable
the depth of indentation to exceed three-quarters of the coating
micrometer stage. The apparatus shall mechanically bring the
film thickness. Start the test cycle so that the indenter is
A hardness tester meeting the apparatus requirements for this method is the
Tukon Microhardness Tester, available from the Wilson Instruments, Inc., Division Available from National Institute of Standards and Technology (NIST), 100
of Instron, 100 Royall St., Canton, MA 02021. Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov.
D1474/D1474M − 13 (2023)
mechanically brought into contact with the mounted specimen 11.1.1 Mean and range of KHN values obtained for each
under a load of 25 g and full load is applied, maintained for specimen, stating the number of indentations made and the
18 seconds 6 0.5 seconds, and removed. For maximum indenter load used,
accuracy, ensure that the indenter has not penetrated the 11.1.2 Mean film thic
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