ASTM D968-93(2001)
(Test Method)Standard Test Methods for Abrasion Resistance of Organic Coatings by Falling Abrasive
Standard Test Methods for Abrasion Resistance of Organic Coatings by Falling Abrasive
SCOPE
1.1 These test methods cover the determination of the resistance of organic coatings to abrasion produced by abrasive falling onto coatings applied to a plane rigid surface, such as a metal or glass panel.
1.2 Two test methods based on different abrasives are covered as follows: SectionsMethod A--Falling Sand Abrasion Test1-12Method B--Falling Silicon Carbide Abrasion Test13-19
1.3 These methods should be restricted to testing in only one laboratory when numerical values are used because of the poor reproducibility of the methods (see 13.1.2 and 21.1.2 ). Interlaboratory agreement is improved significantly when ranking is used in place of numerical values.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D968–93 (Reapproved 2001)
Standard Test Methods for
Abrasion Resistance of Organic Coatings by Falling
Abrasive
This standard is issued under the fixed designation D 968; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope DryFilmThicknessofNonconductiveCoatingsAppliedto
a Nonferrous Metal Base
1.1 These test methods cover the determination of the
E 11 Specification for Wire-Cloth Sieves for Testing Pur-
resistance of organic coatings to abrasion produced by abrasive
poses
falling onto coatings applied to a plane rigid surface, such as a
metal or glass panel.
3. Terminology
1.2 Two test methods based on different abrasives are
3.1 Description of Term Specific to This Standard:
covered as follows:
3.1.1 abrasion resistance—the amount of abrasive required
Sections
to wear through a unit film thickness of the coating.
Method A—Falling Sand Abrasion Test 1-12
Method B—Falling Silicon Carbide Abrasion Test 13-19
4. Summary of Test Methods
1.3 These methods should be restricted to testing in only
4.1 Abrasive is allowed to fall from a specified height
one laboratory when numerical values are used because of the
through a guide tube onto a coated panel until the substrate
poor reproducibility of the methods (see 13.1.2 and 21.1.2).
becomes visible. The amount of abrasive per unit film thick-
Interlaboratoryagreementisimprovedsignificantlywhenrank-
ness is reported as the abrasion resistance of the coating on the
ing is used in place of numerical values.
panel. Silica sand or silicon carbide may be used, as specified.
1.4 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
5. Significance and Use
only.
5.1 Silica sand produces a slower rate of abrasion for
1.5 This standard does not purport to address the safety
organic coatings than provided by silicon carbide but, for some
concerns, if any, associated with its use. It is the responsibility
types of coatings, it provides greater discrimination.
of the user of this standard to establish appropriate safety and
5.2 The abrasion resistance scales produced by the two
health practices and determine the applicability of regulatory
methods differ, but the methods provide approximately the
limitations prior to use.
same rankings of coatings for abrasion resistance.
2. Referenced Documents 5.3 Each of the methods has been found useful for rating the
abrasion resistance of specific types of coatings. For example
2.1 ASTM Standards:
MethodA(falling sand) has been used for rating floor coatings
D 823 Practices for Producing Films of Uniform Thickness
2 while Method B (falling silicon carbide) has been used for
of Paint, Varnish, and Related Products on Test Panels
rating coatings for ship decks.
D 1005 Test Method for Measurement of Dry-Film Thick-
ness of Organic Coatings Using Micrometers
METHOD A—FALLING SAND ABRASION TEST
D 1186 Test Methods for Nondestructive Measurement of
Dry Film Thickness of Nonmagnetic Coatings Applied to
6. Apparatus and Materials
a Ferrous Base
6.1 Abrasion Tester,asillustratedinFig.1andFig.2.Agate
D 1400 Test Method for Nondestructive Measurement of
for starting the flow of abrasive is located near the top of the
guide tube. It consists of a metal disk inserted into a slit in the
side of the guide tube with a collar covering the slit. The guide
tube shall be firmly supported in a vertical position over a
These test methods are under the jurisdiction of ASTM Committee D01 on
Paint and Related Coatings, Materials, and Applications and are the direct
responsibility of Subcommittee D01.23 on Physical Properties of Applied Paint
Films.
Current edition approved Sept. 15, 1993. Published November 1993. Originally Annual Book of ASTM Standards, Vol 14.02.
e1 4
published as D 968 – 48 T. Last previous edition D 968 – 81 (1991) . Hipkins, C. C., and Phain, R. J., “The Falling Sand Abrasion Tester,” ASTM
Annual Book of ASTM Standards, Vol 06.01. Bulletin, No. 143, December 1946, pp. 18–22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D968
opening of the tube is directly above the area to be abraded and
the distance from the tube to the coated surface face at the
nearest point is 25 mm (1 in.) when measured in the vertical
direction. The base of the apparatus shall be fitted with
adjusting screws for properly aligning the equipment.
6.2 Standard Abrasive—Natural silica sand from the St.
Peters or Jordan sandstone deposits (located in the central
UnitedStates)shallbeconsideredstandardwhennotmorethan
15 % of the grains in a sample are retained on a No. 20 (850
µm) sieve and not more than 5% of the grains pass a No. 30
(600 µm) sieve after 5 min of continuous sieving. The sand is
characterized by its roundness of grains and its exceptionally
high silicon dioxide content. Use the sieves described in
Specification E 11.
NOTE 1—Theabradingqualitiesofsandobtainedfromdifferentsources
may differ slightly even though the sand meets the sieve requirements.
Therefore, for maximum precision of test results, purchaser and seller
should use sand from the same source.
7. Test Specimens
7.1 Apply uniform coatings of the material to be tested to a
plane, rigid surface such as a metal or glass panel. Prepare a
minimum of two coated panels for the material.
7.2 Cure the coated panels under the conditions of humidity
and temperature agreed upon between the purchaser and seller.
NOTE 2—The coatings should be applied in accordance with Practices
D 823, or as agreed upon between the purchaser and the seller.
FIG. 1 Apparatus for Falling Sand Abrasion Test
NOTE 3—The thickness of the dry coatings should be measured in
accordance with Test Methods D 1005, D 1186 or D 1400.
8. Standardization
8.1 Pour a quantity of standard sand into the funnel.
Examine the sand stream falling from the lower end of the
guide tube and align the apparatus by means of the adjusting
screws in the base until the inner concentrated core of the sand
stream falls in the center of the flow when viewed at two
positions at 90° to each other. Introduce a measured volume of
sand (2000 6 10 mL is a convenient amount) and determine
the time of efflux. The rate of flow shall be 2 L of sand in 21
to 23.5 s.
8.2 Secure a trial panel in the testing position, as described
in 6.1, and introduce the sand in increments until a spot 4 mm
( ⁄32 in. ) in diameter is worn through to the base material. The
overall abraded area shall be elliptical in shape, about 1 in. (25
mm) in width and 30 mm (1 ⁄4 in.) in length. The center of the
area of maximum abrasion shall be on the center line through
the longer axis of the abraded pattern and within 14 to 17 mm
9 11
( ⁄16to ⁄16 in.) of the top edge. Slight final adjustment of the
instrument may be required to center the abrasion spot in the
pattern.Afinal check on alignment is made by determining the
amount of sand that passes through a 4-mm ( ⁄32-in. ) hole in a
metal panel placed directly under the tube. Place a container
undertheholeinthepanelandallowaweighedamountofsand
NOTE 1—All dimensions are given in inches. 1 in. = 25.4 mm.
to pass through the tube onto the panel. Weigh the amount of
FIG. 2 Design Details of Abrasion Test Apparatus
sand that passed through the hole into the container. The
apparatus can be considered to be in calibration if the amount
suitable receptacle, which shall contain a support for holding of sand that passed through the hole is 90 to 93 % of the
the coated panel at an angle of 45° to the vertical, so that the amount of sand that impinged on the panel.
D968
9. Conditioning 12.1.3 Litres of abrasive used for each area tested,
12.1.4 Coating thickness in mils for each area tested,
9.1 Unless otherwise agreed upon between purchaser and
12.1.5 Abrasion resistance values for each area tested,
seller, condition the coated test panels for at least 24 h at 23 6
12.1.6 Mean abrasion resistance for each coated panel
2°C and 50 6 5 % relative humidity. Conduct the test in the
tested, and
same environment or immediately on removal.
12.
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