1、Designation: D2794 93 (Reapproved 2010)Standard Test Method forResistance of Organic Coatings to the Effects of RapidDeformation (Impact)1This standard is issued under the fixed designation D2794; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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. Scope1.1 This test m
3、ethod covers a procedure for rapidly deform-ing by impact a coating film and its substrate and for evaluatingthe effect of such deformation.1.2 This test method should be restricted to testing in onlyone laboratory when numerical values are used because of thepoor reproducibility of the method. Inte
4、rlaboratory agreementis improved when ranking is used in place of numerical values.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.
5、4 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 A
6、STM Standards:2D609 Practice for Preparation of Cold-Rolled Steel Panelsfor Testing Paint, Varnish, Conversion Coatings, andRelated Coating ProductsD823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD1186 Test Methods for Nondestructive Measu
7、rement ofDry Film Thickness of Nonmagnetic Coatings Applied toa Ferrous Base33. Terminology3.1 Description of Term Specific to This Standard:3.1.1 impact resistance, of a coating, nthe number ofinch-pounds (kilogram-metres) required to produce cracking inthe deformed coating.4. Summary of Test Metho
8、d4.1 The organic coatings under test are applied to suitablethin metal panels. After the coatings have cured, a standardweight is dropped a distance so as to strike an indenter thatdeforms the coating and the substrate. The indentation can beeither an intrusion or an extrusion. By gradually increasi
9、ng thedistance the weight drops, the point at which failure usuallyoccurs can be determined. Films generally fail by cracking,which is made more visible by the use of a magnifier, by theapplication of a copper sulfate (CuSO4) solution on steel, or bythe use of a pin hole detector.5. Significance and
10、 Use5.1 Coatings attached to substrates are subjected to damag-ing impacts during the manufacture of articles and their use inservice. In its use over many years, this test method for impactresistance has been found to be useful in predicting theperformance of organic coatings for their ability to r
11、esistcracking caused by impacts.6. Apparatus6.1 Tester, consisting of a vertical tube to guide a cylindricalweight that is dropped on a punch resting on the test panel.6.1.1 Guide Tube, 24 to 48 in. (0.6 to 1.2 m) long mountedvertically in a base plate. A slot is cut lengthwise on one sideof the tub
12、e to act as a guide for a cylindrical weight that fitsinside the tube. Graduations are marked in inch-pounds alongthe slot. The base is constructed so that a thin flat panel can beinserted at 2 in. (50 mm) below the tube.6.1.2 Weight, metal cylinder, made to fit inside the guidetube. A pin is fitted
13、 into one side of the weight to act as a guideby riding in the slot of the tube and to serve as a handle bywhich the weight can be raised and released and serve as theindicator of inch-pounds (kilogram-metres).1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coat
14、ings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.23 on Physical Properties of Applied Paint Films.Current edition approved Dec. 1, 2010. Published December 2010. Originallyapproved in 1969. Last previous edition approved in 2004 as D2794 93 (2004).DOI: 10.1520/D2
15、794-93R10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this histo
16、rical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2 IndenterA steel punch with a hemispherical headhaving a diameter of either 0.500 in. (12.7 mm) or 0.625 in.(15.9 mm). The head rests on t
17、he test panel and the punch isheld vertically by a guide ring.6.3 Panel SupportA steel fixture with a 0.64-in. (16.3-mm) diameter cylindrical hole centered under the indenter forsupporting the test panel.6.4 Magnifier.6.5 Pin Hole Detector.7. Reagents7.1 An acidified copper sulfate (CuSO4) solution
18、preparedby dissolving 10 g of CuSO45H2Oin90gof1.0N hydro-chloric acid (HCl).8. Test Specimens8.1 Apply uniform coatings of the material to be tested to24-gage (0.025 in. or 0.63 mm) steel panels treated with aconversion coating in accordance with Procedure A of PracticeD609, unless otherwise specifi
19、ed. Prepare a minimum of fourcoated panels for the material.NOTE 1The coatings should be applied in accordance with PracticesD823, or as agreed upon between the producer and the user. Other gagesteel panels may be used if agreed upon between the producer and theuser.8.2 Cure the coated panels under
20、conditions of humidity andtemperature agreed upon between the producer and the user.NOTE 2The thickness of the dry coatings should be measured inaccordance with Test Methods D1186.9. Conditioning9.1 Unless otherwise agreed upon between the producer andthe user, condition the coated test panels for a
21、t least 24 h at 73.56 3.5F (23 6 2C) and 50 6 5 % relative humidity. Conductthe test in the same environment or immediately on removaltherefrom.10. Procedure10.1 Install the punch having the head diameter specified oragreed upon. Place the test panel in the apparatus with thecoated side either up or
22、 down as specified or agreed upon. Besure the panel is flat against the base support and that theindenter is in contact with the top surface of the panel. Lightlyplace the weight on the indenter and adjust the guide tube sothat the lifting pin is at the zero mark. Raise the weight up thetube to a he
23、ight where it is expected that no failure will occur.Release the weight so that it drops on the indenter.10.2 Remove the test panel from the apparatus and observethe impact area for cracks in the coating. If no cracks areevident, repeat the procedure at a greater height, increasing 1in. (25 mm) at a
24、 time. Once visible cracks are observed, repeatthe test five times at each of three heights; slightly above,slightly below, and at that determined in the first trial. Test ina random fashion so that all impacts from one height are notmade in succession or on one panel.10.3 Examine the impacted areas
25、 for cracking by one of thefollowing methods:10.3.1 Use a magnifier to examine the area for cracks.10.3.2 Hold a white flannel-type cloth saturated with theacidified copper sulfate (CuSO4) solution (7.1) over the im-pacted areas for at least 15 min. Remove the cloth and examineboth the test areas an
26、d cloth for evidence of copper depositionor iron-rust staining respectively.NOTE 3The copper sulfate solution will not perform properly onzinc-phosphate-treated metal unless the conversion coating cracks.10.3.3 To detect breaks in the film with a pin hole detector,first connect the ground lead from
27、the instrument to the baresubstrate and connect the instrument to an electrical powersource. Moisten the probe sponge with tap water and slowlydraw the probe over the impact area. The presence of crackswill be indicated by an audible alarm.10.4 For each inch-pound (kilogram-metre) level, tabulatethe
28、 number of times the coating passed or failed. The valuewhere the results change from mainly passing to mainly failingis the impact failure end point.11. Report11.1 Report the following for each coating tested:11.1.1 The inch-pounds (kilogram-metres) at the impactfailure end point,11.1.2 Whether int
29、rusion or extrusion was used,11.1.3 Diameter of the punch used,11.1.4 Thickness of coating,11.1.5 Substrate thickness and type of metal,11.1.6 Method of panel preparation, and11.1.7 Atmospheric conditions under which the coated pan-els were conditioned and tested.NOTE 4Because of the poor reproducib
30、ility of this method, thereporting of inch-pounds (kilogram-metres) in comparing coatings forimpact resistance should be restricted to one laboratory. For interlabora-tory comparisons, rankings of coatings for impact resistance should bereported.12. Precision and Bias12.1 On the basis of an interlab
31、oratory test in whichoperators in six laboratories tested three paints having a broadrange of impact resistance on two metal substrates, thebetween-laboratories coefficients of variation were found to beas follows:Coefficient of VariationIntrusion,%Extrusion,%Brittle coating (less than 6 in.-lb) 25
32、100Average coating (between 6 and 140in.-lb)80 100Flexible coating (more than 140 in.-lb) 10 25(0.625 in.-diameter punch)12.2 BiasSince there is no accepted reference materialsuitable for determining the bias for the procedure in this testmethod, bias cannot be determined.13. Keywords13.1 cracking f
33、ailure; extrusion indentation; intrusion in-dentation; impact failureD2794 93 (2010)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of th
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