1、Designation: D 2794 93 (Reapproved 2004)Standard Test Method forResistance of Organic Coatings to the Effects of RapidDeformation (Impact)1This standard is issued under the fixed designation D 2794; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript 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. Scope1.1 This tes
3、t method 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. I
4、nterlaboratory agreementis improved when ranking is used in place of numerical values.1.3 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 determ
5、ine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 609 Practice for Preparation of Cold-Rolled Steel Panelsfor Testing Paint, Varnish, Conversion Coatings, andRelated Coating ProductsD 823 Practices for Producing Films of Uniform Thicknessof Pain
6、t, Varnish, and Related Products on Test PanelsD 1186 Test Methods for Nondestructive Measurement ofDry Film Thickness of Nonmagnetic Coatings Applied toa Ferrous Base3. Terminology3.1 Description of Term Specific to This Standard:3.1.1 impact resistance, of a coatingthe number of inch-pounds (kilog
7、ram-metres) required to produce cracking in thedeformed coating.4. Summary of Test Method4.1 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 sub
8、strate. The indentation can beeither an intrusion or an extrusion. By gradually increasing 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 su
9、lfate (CuSO4) solution on steel, or bythe use of a pin hole detector.5. Significance and 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 fo
10、und to be useful in predicting theperformance of organic coatings for their ability to resistcracking 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
11、) long mountedvertically in a base plate. A slot is cut lengthwise on one sideof the tube 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
12、the tube.6.1.2 Weight, metal cylinder, made to fit inside the guidetube. A pin is fitted 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).6.
13、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 the test panel and the punch isheld vertically by a guide ring.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Mat
14、erials, and Applications and is the direct responsibility ofSubcommittee D01.23 on Physical Properties of Applied Paint Films.Current edition approved June 1, 2004. Published June 2004. Originallyapproved in 1969. Last previous edition approved in 1999 as D 2794 93 (1999)e1.2For referenced ASTM stan
15、dards, 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
16、PA 19428-2959, United States.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 preparedby dissolving 10 g of CuS
17、O45H2Oin90gof1.0N 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 PracticeD 609, unless otherwise specified. Prepare a minimum of fourcoa
18、ted panels for the material.NOTE 1The coatings should be applied in accordance with PracticesD 823, 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 conditions of humidity andtempe
19、rature agreed upon between the producer and the user.NOTE 2The thickness of the dry coatings should be measured inaccordance with Test Methods D 1186.9. Conditioning9.1 Unless otherwise agreed upon between the producer andthe user, condition the coated test panels for at least 24 h at 73.56 3.5F (23
20、 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 down as specified or agreed u
21、pon. 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 height where it is expected that
22、 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 time. Once visible cracks are
23、 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 for cracking by one of thefol
24、lowing 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 and cloth for evidence of copper
25、 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 the instrument to the baresubs
26、trate 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 number of times the coating p
27、assed 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 intrusion or extrusion was used,1
28、1.1.3 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 reproducibility of this method, therepor
29、ting 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 interlaboratory test in whichoperators
30、 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 100Average coating (between 6
31、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 failure; extrusion indentation;
32、 intrusion in-dentation; impact failureD 2794 93 (2004)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 the validity of any such patent
33、 rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either
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35、ring you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 2794 93 (2004)3
