ASTM D5178-21

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Designation: D5178 − 16 D5178 − 21
Standard Test Method for
Mar Resistance of Organic Coatings
This standard is issued under the fixed designation D5178; 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.
1. Scope Scope*
1.1 This test method covers the determination of the mar resistance on smooth, flat surfaces. Results are expressed in terms of
force-to-mar films of organic coatings such as paint, varnish, and lacquer when applied to smooth, flat planar panel surfaces.
1.2 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D609 Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating
Products
D823 Practices for Producing Films of Uniform Thickness of Paint, Coatings and Related Products on Test Panels
D1005 Test Method for Measurement of Dry-Film Thickness of Organic Coatings Using Micrometers
D1186D2691 Test Methods Method for NondestructiveMicroscopical Measurement of Dry Film Thickness of Nonmagnetic
Coatings Applied to a Ferrous BaseCoatings on Wood Products (Withdrawn 2006)1992)
D1400D7091 Test Method Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied
to Ferrous Metals and Nonmagnetic, Nonconductive Coatings Applied to a Nonferrous Metal BaseNon-Ferrous Metals
(Withdrawn 2006)
D2691 Method for Microscopical Measurement of Dry Film Thickness of Coatings on Wood Products (Withdrawn 1992)
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions:
This test method is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.23 on Physical Properties of Applied Paint Films.
Current edition approved Dec. 1, 2016June 1, 2021. Published January 2017June 2021. Originally approved in 1991. Last previous edition approved in 20132016 as
D5178 – 13.D5178 – 16. DOI: 10.1520/D5178-16.10.1520/D5178-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5178 − 21
3.1.1 mar resistance, n—the ability of a coating to resist damage caused by light abrasion. As just defined, abrasion; it is a
resistance of the surface of the coating to permanent deformation, resulting from the application of a dynamic mechanical force.
4. Summary of Test Method
4.1 The materials under test are applied at uniform thickness to flat panels of uniform surface texture. After drying/curing, the mar
resistance is determined by pushing the panels beneath a rounded stylus or loop that is loaded in increasing amounts loop stylus
at a constant normal load. Increasing (decreasing) loads are applied to the stylus until the coating is marred. marred (not marred).
5. Significance and Use
5.1 In some situations, marring of coatings applied to substrates under typical use conditions is unacceptable. This test method
has been found useful in differentiating the degree of marring of coatings on substrates. It is most useful in providing relative
ratings for a series of coated panels exhibiting significant differences in marring.
5.2 In a limited laboratory study, meaningful mar results were impossible when powder coatings were tested. The mar marking,
that is, scratches, became less perceptible with time. Therefore, powder coatings may not be applicable coatings for this test
method.
6. Apparatus
6.1 Application Equipment, as described in Practices D823.
6.2 Film-Thickness Measuring Apparatus, as described in Test Methods D1005, D1186D2691, D1400, or D2691D7091.
6.3 Balanced Beam Scrape Adhesion and Mar Tester (Fig. 1 and Fig. 2), consisting of a balanced beam to which is secured a
platform for supporting weights, and a rod at an angle of 45° that holds the scraping loop.loop stylus. The rod shall be set so that
the scraping loop stylus contacts test surfaces directly below the weights. The loopweights shall be ⁄16-in. (1.6 mm) diameter rod,
bent into a “U” shape with an outside radius of 0.128 6 0.002 in. (3.25 6 0.05 mm) and hardened to Rockwell HRC 56 to 58,
and shall be a smooth finish. The loop can be either chromium plated, nickel plated, or heat treated polished steel as agreed upon
between the purchaser and the supplier. These testers are adjustable to accommodate flat, metallic, and nonmetallic specimens to
0.5-in. (12-mm) thick and 4 to 16 in. (100 to 400 mm) wide and long; the specimen should be at least in increments of 0.5 kg up
to a maximum load of 10 kg. ⁄2-in. (12-mm) wide.
6.3.1 Loop Stylus, the loop shall be ⁄16 in. (1.6 mm) diameter rod, bent into a “U” shape with an outside radius of 0.128 in. 6
0.002 in. (3.25 mm 6 0.05 mm) and hardened to Rockwell HRC 56 to 58, and shall be a smooth finish. The loop can be either
chromium plated, nickel plated, or heat treated polished steel as agreed upon between the interested parties.
FIG. 1 Balanced Beam Scrape Adhesion and Mar Tester
D5178 − 21
FIG. 2 Balanced Beam Scrape Adhesion and Mar Tester
7. Preparation of Specimens
7.1 Panels shall be flat, and either metallic or nonmetallic panels as agreed upon by the interested parties. If no panel material is
specified, use 0.032 in. (0.8 mm) cold-rolled carbon steel prepared in accordance with Methods B or C of Practice D609.
7.1.1 Typical panel dimensions are 4 in. (100 mm) wide by 6 in. (150 mm) or 8 in. (200 mm) long and a thickness of 0.5 in. (12
mm) or less. Other panel dimensions are acceptable, provided they accommodate sufficient tests as specified in 9.3 – 9.5.
7.2 Apply the materials under test to panels of the composition and surface condition on which it is desired to determine mar
resistance of the coating. The panel material (7.1.1), surface preparation, thickness, and number of coats shall be specified or agreed
upon between the seller and the purchaser. interested parties. Apply coatings and air dry or bake under conditions of humidity and
temperature mutually agreeable to the seller and the purchaser.interested parties.
7.1.1 The surface of the coating must be hard enough to resist damage by the scraping loop at a load agreed upon between the
producer and the user. If no panel material is specified, use 0.032-in. (0.8-mm) cold-rolled carbon steel prepared in accordance with
Methods B or C of Practice D609.
8. Conditioning and Number of Tests
8.1 Condition the test panels for at least 48 h at 2323°C 6 2°C (73.5(73.5°F 6 3.5°F) and 5050 % 6 5 % relative humidity, and
test in the same environment, or immediately on removal therefrom, unless otherwise specified or agreed upon by the seller and
the purchaser. interested parties. Test at least two replicate specimens of each material.
9. Procedure
9.1 In preparation for using the apparatus, ensure that it is reasonably level and place it so that the weight holder is toward the
operator. This places the beam release on the operator’s right and allows freedom to operator to allow the operator freedom to
manually move the test specimen manually under the weighted scraping element (loop). Insert the loop into the holder as far as
TABLE 1 Film Thickness (microns)
Repeatability Reproducibility
Standard Standard Repeatability Reproducibility
Material A
Average
Deviation Deviation Limit Limit
¯
X s S r R
r R
B
Panel Set E and R 109.9 32.2 37.5 90.2 105.0
B
Panel Set B and H 93.3 10.9 10.9 30.4 30.6
B
Panel Set D and G 74.0 25.2 25.2 70.4 70.4
A
The average of the laboratories’ averages.
B
Five laboratories reported results.
D5178 − 21
TABLE 2 Load at the Mar Failure End Point (kg)
Repeatability Reproducibility
Standard Standard Repeatability Reproducibility
Material A
Average
Deviation Deviation Limit Limit
¯
X s S r R
r R
B
Panel Set E and R 7.05 0.88 1.98 2.46 5.55
B
Panel Set B and H 1.52 1.34 1.34 3.75 3.75
Panel Set D and G 1.25 0.93 0.93 2.60 2.60
A
The average of the laboratories’ averages.
B
...