ASTM D4541-2009 Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers.pdf

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1、Designation: D 4541 09Standard Test Method forPull-Off Strength of Coatings Using Portable AdhesionTesters1This standard is issued under the fixed designation D 4541; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last

2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers a procedure for evaluating thepull-off strength (commonly referred to as adhesion) of acoating sy

3、stem from metal substrates. Pull-off strength ofcoatings from concrete is described in Test Method D 7234.The test determines either the greatest perpendicular force (intension) that a surface area can bear before a plug of materialis detached, or whether the surface remains intact at a pre-scribed

4、force (pass/fail). Failure will occur along the weakestplane within the system comprised of the test fixture, adhesive,coating system, and substrate, and will be exposed by thefracture surface. This test method maximizes tensile stress ascompared to the shear stress applied by other methods, such as

5、scratch or knife adhesion, and results may not be comparable.NOTE 1The procedure in this standard was developed for metalsubstrates, but may be appropriate for other rigid substrates such as plasticand wood. Factors such as loading rate and flexibility of the substrate mustbe addressed by the user/s

6、pecifier.1.2 Pull-off strength measurements depend upon both ma-terial and instrumental parameters. Results obtained by eachtest method may give different results. Results should only beassessed for each test method and not be compared with otherinstruments. There are five instrument types, identifi

7、ed as TestMethods B-F. It is imperative to identify the test method usedwhen reporting results.NOTE 2Method A, which appeared in previous versions of thisstandard, has been eliminated as its main use is for testing on concretesubstrates (see Test Method D 7234).1.3 This test method uses a class of a

8、pparatus known asportable pull-off adhesion testers.2They are capable of apply-ing a concentric load and counter load to a single surface sothat coatings can be tested even though only one side isaccessible. Measurements are limited by the strength of adhe-sion bonds between the loading fixture and

9、the specimensurface or the cohesive strengths of the adhesive, coatinglayers, and substrate.1.4 This test can be destructive and spot repairs may benecessary.1.5 The values stated in MPa (inch-pound) units are to beregarded as the standard. The values given in parentheses arefor information only.1.6

10、 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Docu

11、ments2.1 ASTM Standards:3D 2651 Guide for Preparation of Metal Surfaces for Adhe-sive BondingD 3933 Guide for Preparation of Aluminum Surfaces forStructural Adhesives Bonding (Phosphoric Acid Anodiz-ing)D 3980 Practice for Interlaboratory Testing of Paint andRelated Materials4D 7234 Test Method for

12、Pull-Off Adhesion Strength ofCoatings on Concrete Using Portable Pull-Off AdhesionTestersE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ANSI Standard:N512 Protective Coatings (Paints) for the Nuclear Industry52.3 ISO Standard:ISO 4624 Paints and

13、VarnishPull-Off Test for Adhesion51This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.Current edition approved Feb. 1, 2009. Published Apri

14、l 2009. Originallyapproved in 1993. Last previous edition approved in 2002 as D 4541 02.2The term adhesion tester may be somewhat of a misnomer, but its adoption bytwo manufacturers and at least two patents indicates continued usage.3For referenced ASTM standards, visit the ASTM website, www.astm.or

15、g, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.5Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www

16、.ansi.org.1*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.3. Summary of Test Method3.1 The general pull-off test is performed by securing aloading fixture (dolly, stud

17、) normal (perpendicular) to thesurface of the coating with an adhesive. After the adhesive iscured, a testing apparatus is attached to the loading fixture andaligned to apply tension normal to the test surface. The forceapplied to the loading fixture is then gradually increased andmonitored until ei

18、ther a plug of material is detached, or aspecified value is reached. When a plug of material is detached,the exposed surface represents the plane of limiting strengthwithin the system. The nature of the failure is qualified inaccordance with the percent of adhesive and cohesive failures,and the actu

19、al interfaces and layers involved. The pull-offstrength is computed based on the maximum indicated load,the instrument calibration data, and the original surface areastressed. Pull-off strength results obtained using differentdevices may be different because the results depend oninstrumental paramet

20、ers (see Appendix X1).4. Significance and Use4.1 The pull-off strength of a coating is an importantperformance property that has been used in specifications. Thistest method serves as a means for uniformly preparing andtesting coated surfaces, and evaluating and reporting theresults. This test metho

21、d is applicable to any portable apparatusmeeting the basic requirements for determining the pull-offstrength of a coating.4.2 Variations in results obtained using different devices ordifferent substrates with the same coating are possible (seeSection 10). Therefore, it is recommended that the type o

22、fapparatus and the substrate be mutually agreed upon betweenthe interested parties.4.3 The purchaser or specifier shall designate a specific testmethod, that is, B, C, D, E, or F when calling out this standard.5. Apparatus5.1 Adhesion Tester, commercially available, or comparableapparatus specific e

23、xamples of which are listed in AnnexA1-Annex A5.5.1.1 Loading Fixtures, having a flat surface on one end thatcan be adhered to the coating and a means of attachment to thetester on the other end.5.1.2 Detaching Assembly (adhesion tester), having a cen-tral grip for engaging the fixture.5.1.3 Base, o

24、n the detaching assembly, or an annular bearingring if needed for uniformly pressing against the coatingsurface around the fixture either directly, or by way of anintermediate bearing ring. A means of aligning the base isneeded so that the resultant force is normal to the surface.5.1.4 Means of movi

25、ng the grip away from the base in assmooth and continuous a manner as possible so that a torsionfree, co-axial (opposing pull of the grip and push of the basealong the same axis) force results between them.5.1.5 Timer, or means of limiting the loading rate to 1 MPa/s(150 psi/s) or less for a 20 mm l

26、oading fixture so that the testis completed in about 100 s or less. A timer is the minimumequipment when used by the operator along with the forceindicator in 5.1.6.5.1.6 Force Indicator and Calibration Information, fordetermining the actual force delivered to the loading fixture.5.2 Solvent, or oth

27、er means for cleaning the loading fixturesurface. Finger prints, moisture, and oxides tend to be theprimary contaminants.5.3 Fine Sandpaper, or other means of cleaning the coatingthat will not alter its integrity by chemical or solvent attack. Ifany light sanding is anticipated, choose only a very f

28、ine gradeabrasive (400 grit or finer) that will not introduce flaws or leavea residue.5.4 Adhesive6, for securing the fixture to the coating thatdoes not affect the coating properties. Two component epoxiesand acrylics have been found to be the most versatile.5.5 Magnetic or Mechanical Clamps, if ne

29、eded, for holdingthe fixture in place while the adhesive cures.5.6 Cotton Swabs, or other means for removing excessadhesive and defining the adhered area. Any method forremoving excess adhesive that damages the surface, such asscoring (see 6.7), must generally be avoided since inducedsurface flaws m

30、ay cause premature failure of the coating.5.7 Circular Hole Cutter (optional), to score through to thesubstrate around the loading fixture.6. Test Preparation6.1 The method for selecting the coating sites to be preparedfor testing depends upon the objectives of the test andagreements between the con

31、tracting parties. There are, how-ever, a few physical restrictions imposed by the general methodand apparatus. The following requirements apply to all sites:6.1.1 The selected test area must be a flat surface largeenough to accommodate the specified number of replicate tests.The surface may have any

32、 orientation with reference togravitational pull. Each test site must be separated by at leastthe distance needed to accommodate the detaching apparatus.The size of a test site is essentially that of the secured loadingfixture. At least three replications are usually required in orderto statisticall

33、y characterize the test area.6.1.2 The selected test areas must also have enough perpen-dicular and radial clearance to accommodate the apparatus, beflat enough to permit alignment, and be rigid enough to supportthe counter force. It should be noted that measurements closeto an edge may not be repre

34、sentative of the coating as a whole.6.2 Since the rigidity of the substrate affects pull-offstrength results and is not a controllable test variable in fieldmeasurements, some knowledge of the substrate thickness andcomposition should be reported for subsequent analysis orlaboratory comparisons. For

35、 example, steel substrate of lessthan 3.2 mm (18 in.) thickness usually reduces pull-off strengthresults compared to 6.4 mm (14-in.) thick steel substrates.6.3 Subject to the requirements of 6.1, select representativetest areas and clean the surfaces in a manner that will not affectintegrity of the

36、coating or leave a residue. To reduce the risk ofglue failures, the surface of the coating can be lightly abradedto promote adhesion of the adhesive to the surface. If thesurface is abraded, care must be taken to prevent damage to the6Scotch Weld 420, available from 3M, Adhesives, Coatings and Seale

37、rs Div.,3M Center, St. Paul, MN 55144, was used in the round robin.D4541092coating or significant loss of coating thickness. Solvent cleanthe area to remove particulates after abrading. Select a solventthat does not compromise the integrity of the coating.6.4 Clean the loading fixture surface as ind

38、icated by theapparatus manufacturer. Failures at the fixture-adhesive inter-face can often be avoided by treating the fixture surfaces inaccordance with an appropriate ASTM standard practice forpreparing metal surfaces for adhesive bonding.NOTE 3Guides D 2651 and D 3933 are typical of well-proven me

39、th-ods for improving adhesive bond strengths to metal surfaces.6.5 Prepare the adhesive in accordance with the adhesivemanufacturers recommendations. Apply the adhesive to thefixture or the surface to be tested, or both, using a methodrecommended by the adhesive manufacturer. Be certain toapply the

40、adhesive across the entire surface. Position fixture onthe surface to be tested. Carefully remove the excess adhesivefrom around the fixture. (WarningMovement, especiallytwisting, can cause tiny bubbles to coalesce into large holidaysthat constitute stress discontinuities during testing.)NOTE 4Addin

41、g about 1 percent of #5 glass beads to the adhesiveassists in even alignment of the test fixture to the surface.6.6 Based on the adhesive manufacturers recommendationsand the anticipated environmental conditions, allow enoughtime for the adhesive to set up and reach the recommendedcure. During the a

42、dhesive set and early cure stage, a constantcontact pressure should be maintained on the fixture. Magneticor mechanical clamping systems work well, but systemsrelying on tack, such as masking tape, should be used with careto ensure that they do not relax with time and allow air tointrude between the

43、 fixture and the test area.6.7 Scoring around the fixture violates the fundamental insitu test criterion that an unaltered coating be tested. If scoringaround the test surface is employed, extreme care is required toprevent micro-cracking in the coating, since such cracks maycause reduced adhesion v

44、alues. Scored samples constitute adifferent test, and this procedure should be clearly reportedwith the results. Scoring is only recommended for thicker-filmcoatings, that is, thicknesses greater than 500 m (20 mils),reinforced coatings and elastomeric coatings. Scoring, if per-formed, shall be done

45、 in a manner that ensures the cut is madenormal to the coating surface and in a manner that does nottwist or torque the test area and minimizes heat generated andedge damage or microcracks to the coating and the substrate.For thick coatings it is recommended to cool the coating andsubstrate during t

46、he cutting process with water lubrication.NOTE 5A template made from plywood with a hole of the same sizedrilled through it has been found to be an effective method to limitsideways movement of the drill bit.6.8 Note the approximate temperature and relative humidityduring the time of test.7. Test Pr

47、ocedure7.1 Test Methods:7.1.1 Test Method A (discontinued).7.1.2 Test Method B Fixed Alignment Adhesion TesterType II:7.1.2.1 Operate the instrument in accordance with AnnexA1.7.1.3 Test Method C Self-Alignment Adhesion Tester TypeIII:7.1.3.1 Operate the instrument in accordance with AnnexA2.7.1.4 T

48、est Method D Self-Alignment Adhesion Tester TypeIV:7.1.4.1 Operate the instrument in accordance with AnnexA3.7.1.5 Test Method E Self-Alignment Adhesion Tester TypeV:7.1.5.1 Operate the instrument in accordance with AnnexA4.7.1.6 Test Method F Self-Alignment Adhesion Tester TypeVI:7.1.6.1 Operate th

49、e instrument in accordance with AnnexA5.7.2 Select an adhesion-tester with a detaching assemblyhaving a force calibration spanning the range of expectedvalues along with its compatible loading fixture. Mid-rangemeasurements are usually the best, but read the manufacturersoperating instructions before proceeding.7.3 If a bearing ring or comparable device (5.1.3)istobeused, place it concentrically around the loading fixture on thecoating surface. If shims are required when a bearing ring isemployed, place them between the tester base and bearing ringrather than o