1、Designation: D 4541 02Standard 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for evaluating thepull-off strength (commonly referred to as adhesion) of acoating on
3、 rigid substrates such as metal, concrete or wood.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 force (pass/fail). Failure will occur along the weakestp
4、lane 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 asscratch or knife adhesion, and results may not be compar
5、able.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, identified a
6、s TestMethods A-E. It is imperative to identify the test method usedwhen reporting results.1.3 This test method uses a class of apparatus 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 eve
7、n though only one side isaccessible. Measurements are limited by the strength of adhe-sion bonds between the loading fixture and 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 value
8、s stated in MPa (inch-pound) units are to beregarded as the standard. The values given in parentheses arefor information only.1.6 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 ap
9、pro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 2651 Guide for Preparation of Metal Surfaces for Adhe-sive Bonding3D 3933 Guide for Preparation of Aluminum Surfaces forStructural Adhesives Bond
10、ing (Phosphoric Acid Anodiz-ing)3D 3980 Practice for Interlaboratory Testing of Paint andRelated Materials42.2 ANSI Standard:N512 Protective Coatings (Paints) for the Nuclear Industry52.3 ISO Standard:4624 Paints and VarnishPull-Off Test for Adhesion53. Summary of Test Method3.1 The general pull-off
11、 test is performed by securing aloading fixture (dolly, stud) 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 loadi
12、ng fixture is then gradually increased andmonitored until either 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 wit
13、h the percent of adhesive and cohesive failures,and the actual 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 different1This test met
14、hod 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. 10, 2002. Published April 2002. Originallypublished as D 4541 93. Last
15、previous edition D 4541 951.2The term adhesion tester may be somewhat of a misnomer, but its adoption bytwo manufacturers and at least two patents indicates continued usage.3Annual Book of ASTM Standards, Vol 15.06.4Annual Book of ASTM Standards, Vol 06.01.5Available from American National Standards
16、 Institute, 11 W. 42nd St., 13thFloor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.devices may be different because the results depend oninstrumental parameters (see Appendix X1).4. Significance and Use4.1 The
17、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 method is applicable to any portable apparatusmeeting the
18、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 (seeAppendix X1). Therefore, it is recommended that the type ofapparatus and the substrate be mutually agreed upon
19、 betweenthe interested parties.4.3 The purchaser or specifier shall designate a specific testmethod, that is,A, B, C, D or E, when calling out this standard.5. Apparatus5.1 Adhesion Tester, commercially available, or comparableapparatus specific examples of which are listed in AnnexA1-Annex A5.5.1.1
20、 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, on the detaching assembly, or an annular bearingring i
21、f 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 moving the grip away from the base in assmooth and contin
22、uous 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 rate of stress to lessthan 1 MPa/s (150 psi/s) so that the maximum stress is obtainedin less than about 100 s
23、. A timer is the minimum equipmentwhen used by the operator along with the force indicator in5.1.6.NOTE 1Obtaining the maximum stress in 100 s or less by keeping themaximum rate of shear to less than 1 MPa/s (150 psi/s) is valid for thelevels of pull-off strength measured with these types of apparat
24、uses.5.1.6 Force Indicator and Calibration Information, fordetermining the actual force delivered to the loading fixture.5.2 Solvent, or other means for cleaning the loading fixturesurface. Finger prints, moisture, and oxides tend to be theprimary contaminants.5.3 Fine Sandpaper, or other means of c
25、leaning the coatingthat will not alter its integrity by chemical or solvent attack. Ifany light sanding is anticipated, choose only a very fine gradeabrasive (400 grit or finer) that will not introduce flaws or leavea residue.5.4 Adhesive, for securing the fixture to the coating that doesnot affect
26、the coating properties. Two component epoxies6andacrylics7have been found to be the most versatile.5.5 Magnetic or Mechanical Clamps, if needed, 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 me
27、thod forremoving excess adhesive that damages the surface, such asscoring (see 6.7), must generally be avoided since inducedsurface flaws may 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
28、 The method for selecting the coating sites to be preparedfor testing depends upon the objectives of the test andagreements between the contracting parties. There are, how-ever, a few physical restrictions imposed by the general methodand apparatus. The following requirements apply to all sites:6.1.
29、1 The selected test area must be a flat surface largeenough to accommodate the specified number of replicate tests.The surface may have any orientation with reference togravitational pull. Each test site must be separated by at leastthe distance needed to accommodate the detaching apparatus.The size
30、 of a test site is essentially that of the secured loadingfixture. At least three replications are usually required in orderto statistically 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
31、to permit alignment, and be rigid enough to supportthe counter force. It should be noted that measurements closeto an edge may not be representative 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 fieldmeas
32、urements, some knowledge of the substrate thickness andcomposition should be reported for subsequent analysis orlaboratory comparisons. For example, steel substrate of lessthan 3.2 mm (18-in.) thickness usually reduce pull-off strengthresults compared to 6.4 mm (14-in.) thick steel substrates.6.3 Su
33、bject to the requirements of 6.1, select representativetest areas and clean the surfaces in a manner that will not affectintegrity of the coating or leave a residue. Surface abrasionmay introduce flaws and should generally be avoided. A fineabrasive (see 5.3) should only be used if needed to removel
34、oose or weakly adhered surface contaminants.6.4 Clean the loading fixture surface as indicated 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 su
35、rfaces for adhesive bonding.6Araldite Adhesive, available from Ciba-Geigy Plastics, Duxford, Cambridge,CB2 4QA, England, Hysol Epoxy Patch Kit 907, available from Hysol Div., TheDexter Corp., Willow Pass Rd., Pittsburg, CA 94565, and Scotch Weld Adhesive1838B/A, available from 3M, Adhesives, Coating
36、s and Sealers Div., 3M Center, St.Paul, MN 55144, have been found satisfactory for this purpose.7Versiloc 201 and 204 with accelerator, available from Lord Corp., IndustrialAdhesive Div., 2000 W. Grandview Blvd., P.O. Box 10038, Erie, PA 16514, havebeen found satisfactory for this purpose.D4541022NO
37、TE 2Guides D 2651 and D 3933 are typical of well-proven meth-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 methodrecomme
38、nded by the adhesive manufacturer. Be certain toapply the 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 con
39、stitute stress discontinuities during testing.)NOTE 3Adding 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 adhe
40、sive to set up and reach the recommendedcure. During the adhesive 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
41、do not relax with time and allow air tointrude between the fixture and the test area.6.7 Scoring around the fixture violates the fundamentalin-situ test criterion that an unaltered coating be tested. Ifscoring around the test surface is employed, extreme care isrequired to prevent micro-cracking in
42、the coating, since suchcracks may cause reduced adhesion values. Scored samplesconstitute a different test, and this procedure should be clearlyreported with the results.NOTE 4It is common to score around the test fixture when performingtests on cementitious substrates where the tensile strength of
43、the substrateis significantly lower than either the pull-off or cohesive strength of thecoating system.6.8 Note the approximate temperature and relative humidityduring the time of test.7. Test Procedure7.1 Test Methods:7.1.1 Test Method A Fixed Alignment Adhesion TesterType I:7.1.1.1 Operate the ins
44、trument in accordance with AnnexA1.7.1.2 Test Method B Fixed Alignment Adhesion TesterType II:7.1.2.1 Operate the instrument in accordance with AnnexA2.7.1.3 Test Method C Self-Alignment Adhesion Tester TypeIII:7.1.3.1 Operate the instrument in accordance with AnnexA3.7.1.4 Test Method D Self-Alignm
45、ent Adhesion Tester TypeIV:7.1.4.1 Operate the instrument in accordance with AnnexA4.7.1.5 Test Method E Self-Alignment Adhesion Tester TypeV:7.1.5.1 Operate the instrument in accordance with AnnexA5.7.2 Select an adhesion-tester with a detaching assemblyhaving a force calibration spanning the range
46、 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
47、surface. If shims are required when a bearing ring isemployed, place them between the tester base and bearing ringrather than on the coating surface.7.4 Carefully connect the central grip of the detachingassembly to the loading fixture without bumping, bending, orotherwise prestressing the sample an
48、d connect the detachingassembly to its control mechanism, if necessary. For nonhori-zontal surfaces, support the detaching assembly so that itsweight does not contribute to the force exerted in the test.7.5 Align the device according to the manufacturers in-structions and set the force indicator to
49、zero.NOTE 5Proper alignment is critical, see Appendix X2. If alignment isrequired, use the procedure recommended by the manufacturer of theadhesion tester and report the procedure used.7.6 Increase the load to the fixture in as smooth andcontinuous a manner as possible, at a rate of less than 1 MPa/s(150 psi/s) so that failure occurs or the maximum stress isreached in about 100 s or less (see Note 1).7.7 Record the force attained at failure or the maximumforce applied.7.8 If a plug of material is detached, label and store thefixture for qualification of the fai
