ASTM D2794-93(1999)e1

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e1
Designation: D 2794 – 93 (Reapproved 1999)
Standard Test Method for
Resistance of Organic Coatings to the Effects of Rapid
Deformation (Impact)
This standard is issued under the fixed designation D 2794; 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—Deleted reference to multiple sources in former Footnotes 3 and 4 in December 1999.
1. Scope weight is dropped a distance so as to strike an indenter that
deforms the coating and the substrate. The indentation can be
1.1 This test method covers a procedure for rapidly deform-
either an intrusion or an extrusion. By gradually increasing the
ing by impact a coating film and its substrate and for evaluating
distance the weight drops, the point at which failure usually
the effect of such deformation.
occurs can be determined. Films generally fail by cracking,
1.2 This test method should be restricted to testing in only
which is made more visible by the use of a magnifier, by the
one laboratory when numerical values are used because of the
application of a copper sulfate (CuSO ) solution on steel, or by
poor reproducibility of the method. Interlaboratory agreement
the use of a pin hole detector.
is improved when ranking is used in place of numerical values.
1.3 This standard does not purport to address the safety
5. Significance and Use
concerns, if any, associated with its use. It is the responsibility
5.1 Coatings attached to substrates are subjected to damag-
of the user of this standard to establish appropriate safety and
ing impacts during the manufacture of articles and their use in
health practices and determine the applicability of regulatory
service. In its use over many years, this test method for impact
limitations prior to use.
resistance has been found to be useful in predicting the
2. Referenced Documents performance of organic coatings for their ability to resist
cracking caused by impacts.
2.1 ASTM Standards:
D 609 Practice for Preparation of Cold-Rolled Steel Panels
6. Apparatus
for Testing Paint, Varnish, Conversion Coatings, Lacquer,
2 6.1 Tester, consisting of a vertical tube to guide a cylindrical
and Related Coating Products
weight that is dropped on a punch resting on the test panel.
D 823 Practices for Producing Films of Uniform Thickness
2 6.1.1 Guide Tube, 24 to 48 in. (0.6 to 1.2 m) long mounted
of Paint, Varnish, and Related Products on Test Panels
vertically in a base plate. A slot is cut lengthwise on one side
D 1186 Test Methods for Nondestructive Measurement of
of the tube to act as a guide for a cylindrical weight that fits
Dry Film Thickness of Nonmagnetic Coatings Applied to
2 inside the tube. Graduations are marked in inch-pounds along
a Ferrous Base
the slot. The base is constructed so that a thin flat panel can be
3. Terminology inserted at 2 in. (50 mm) below the tube.
6.1.2 Weight, metal cylinder, made to fit inside the guide
3.1 Description of Term Specific to This Standard:
tube. A pin is fitted into one side of the weight to act as a guide
3.1.1 impact resistance, of a coating—the number of inch-
by riding in the slot of the tube and to serve as a handle by
pounds (kilogram-metres) required to produce cracking in the
which the weight can be raised and released and serve as the
deformed coating.
indicator of inch-pounds (kilogram-metres).
4. Summary of Test Method
6.2 Indenter—A steel punch with a hemispherical head
having a diameter of either 0.500 in. (12.7 mm) or 0.625 in.
4.1 The organic coatings under test are applied to suitable
(15.9 mm). The head rests on the test panel and the punch is
thin metal panels. After the coatings have cured, a standard
held vertically by a guide ring.
6.3 Panel Support—A steel fixture with a 0.64-in. (16.3-
This test method is under the jurisdiction of ASTM Committee D-1 on Paint
mm) diameter cylindrical hole centered under the indenter for
and Related Coatings, Materials, and Applications and is the direct responsibility of
supporting the test panel.
Subcommittee D01.23 on Physical Properties of Applied Paint Films.
6.4 Magnifier.
Current edition approved Sept. 15, 1993. Published November 1993. Originally
6.5 Pin Hole Detector.
published as D 2794 – 69. Last previous edition D 2794 – 92.
Annual Book of ASTM Standards, Vol 06.01.
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D 2794
7. Reagents both the test areas and cloth for evidence of copper deposition
or iron-rust staining respectively.
7.1 An acidified copper sulfate (CuSO ) solution prepared
by dissolving 10 g of CuSO ·5H Oin90gof1.0 N hydro-
NOTE 3—The copper sulfate solution will not perform properly on
4 2
chloric acid (HCl). zinc-phosphate-treated metal unless the conversion coating cracks.
10.3.3 To detect breaks in the film with a pin hole detector,
8. Test Specimens
first connect the ground lead from the instrument to the bare
8.1 Apply uniform coatings of the material to be tested to
substrate and connect the instrument to an electrical power
24-gage (0.025 in. or 0.63 mm) steel pane
...