1、Designation: D968 05 (Reapproved 2010)Standard Test Methods forAbrasion Resistance of Organic Coatings by FallingAbrasive1This standard is issued under the fixed designation D968; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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 These test methods cover the
3、 determination of theresistance of organic coatings to abrasion produced by abrasivefalling onto coatings applied to a plane rigid surface, such as ametal or glass panel.1.2 Two test methods based on different abrasives arecovered as follows:SectionsMethod AFalling Sand Abrasion Test 1-12Method BFal
4、ling Silicon Carbide Abrasion Test 13-191.3 These methods should be restricted to testing in onlyone laboratory when numerical values are used because of thepoor reproducibility of the methods (see 13.1.2 and 21.1.2).Interlaboratory agreement is improved significantly when rank-ing is used in place
5、of numerical values.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 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
6、establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD1005 Test Method for Measure
7、ment of Dry-Film Thick-ness of Organic Coatings Using MicrometersD1186 Test Methods for Nondestructive Measurement ofDry Film Thickness of Nonmagnetic Coatings Applied toa Ferrous Base3D1400 Test Method for Nondestructive Measurement ofDry Film Thickness of Nonconductive CoatingsApplied toa Nonferro
8、us Metal Base3E11 Specification for Woven Wire Test Sieve Cloth and TestSieves2.2 Other Standards:ANSI B74.12 Specifications for the Size of AbrasiveGrain Grinding Wheels, Polishing and General Indus-trial Uses442-GB-1984-R1993 FEPA Standard for bonded abrasivegrains of fused aluminum oxide and sili
9、con carbide53. Terminology3.1 Description of Term Specific to This Standard:3.1.1 abrasion resistance, nthe amount of abrasive re-quired to wear through a unit film thickness of the coating.4. Summary of Test Method4.1 Abrasive is allowed to fall from a specified heightthrough a guide tube onto a co
10、ated panel until the substratebecomes visible. The amount of abrasive per unit film thick-ness is reported as the abrasion resistance of the coating on thepanel. Silica sand or silicon carbide may be used, as specified.5. Significance and Use5.1 Silica sand produces a slower rate of abrasion fororga
11、nic coatings than that provided by silicon carbide. Forsome types of coatings, it also provides greater differentiation.5.2 The abrasion resistance scales produced by the twomethods differ, but the methods provide approximately thesame rankings of coatings for abrasion resistance.5.3 Each of the met
12、hods has been found useful for rating theabrasion resistance of specific types of coatings. For exampleMethod A (falling sand) has been used for rating floor coatings1These test methods are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings, Materials, and Applications and are
13、 the directresponsibility of Subcommittee D01.23 on Physical Properties of Applied PaintFilms.Current edition approved Dec. 1, 2010. Published December 2010. Originallyapproved in 1948. Last previous edition approved in 2005 as D968 051. DOI:10.1520/D0968-05R10.2For referenced ASTM standards, visit
14、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 historical standard is referencedon www.astm.org.4Ava
15、ilable from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.5Available from The British Abrasive Federation, Trafford Park Road, TraffordPark, Manchester M17 1JD, England.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
16、 West Conshohocken, PA 19428-2959, United States.while Method B (falling silicon carbide) has been used forrating coatings for ship decks.METHOD AFALLING SAND ABRASION TEST66. Apparatus and Materials6.1 Abrasion Tester, as illustrated in Fig. 1 and Fig. 2.Agatefor starting the flow of abrasive is lo
17、cated near the top of theguide tube. It consists of a metal disk inserted into a slit in theside of the guide tube with a collar covering the slit. The guidetube shall be firmly supported in a vertical position over asuitable receptacle, which shall contain a support for holdingthe coated panel at a
18、n angle of 45 to the vertical. The openingof the tube is directly above the area to be abraded and thedistance from the tube to the coated surface face at the nearestpoint is 25 mm (1 in.) when measured in the vertical direction.The base of the apparatus shall be fitted with adjusting screwsfor prop
19、erly aligning the equipment.6.2 Standard AbrasiveNatural silica sand from the St.Peters or Jordan sandstone deposits (located in the centralUnited States) shall be considered standard when graded asfollows after 5 min of continuous sieving.0 % retained on a No. 16 (1.18 mm) sieveMaximum 15 % retaine
20、d on a No. 20 (850 m) sieveMinimum 80 % retained on a No. 30 (600 m) sieveMaximum 5 % passing a No. 30 (600 m) sieveThe sand is characterized by its roundness of grains and hasa silicon dioxide content greater than 99 %. Use the sievesdescribed in Specification E11.NOTE 1The abrading qualities of sa
21、nd obtained from different sourcesmay differ slightly even though the sand meets the sieve requirements.Therefore, for maximum precision of test results, purchaser and sellershould use sand from the same source.7. Test Specimens7.1 Apply uniform coatings of the material to be tested to aplane, rigid
22、 surface such as a metal or glass panel. Prepare aminimum of two coated panels for the material.7.2 Cure the coated panels under the conditions of humidityand temperature agreed upon between the purchaser and seller.NOTE 2The coatings should be applied in accordance with PracticesD823, or as agreed
23、upon between the purchaser and the seller.NOTE 3The thickness of the dry coatings should be measured inaccordance with Test Methods D1005, D1186 or D1400.8. Standardization8.1 Pour a quantity of standard sand into the funnel andexamine the sand stream falling from the lower end of theguide tube. Ali
24、gn the apparatus by means of the adjustingscrews in the base until the inner concentrated core of the sandstream falls in the center of the flow when viewed at twopositions at 90 to each other. Introduce a measured volume ofsand (2000 6 10 mL is a convenient amount) and determinethe time of efflux.
25、The rate of flow shall be 2 L of sand in 21to 23.5 s.8.2 Secure a trial panel in the testing position, as describedin 6.1, and introduce the sand in increments until a spot 4 mm(532 in.) in diameter is worn through to the base material. The6Hipkins, C. C., and Phain, R. J., “The Falling Sand Abrasio
26、n Tester,” ASTMBulletin, No. 143, December 1946 , pp. 1822.FIG. 1 Apparatus for Falling Sand Abrasion TestNOTE 1All dimensions are given in inches. 1 in. = 25.4 mm.FIG. 2 Design Details of Abrasion Test ApparatusD968 05 (2010)2overall abraded area shall be elliptical in shape, about 1 in. (25mm) in
27、width and 30 mm (114 in.) in length. The center of thearea of maximum abrasion shall be on the centerline throughthe longer axis of the abraded pattern and within 14 to 17 mm(916 to1116 in.) of the top edge. Slight final adjustment of theinstrument may be required to center the abrasion spot in thep
28、attern. A final check on alignment is made by determining theamount of sand that passes through a 4-mm (532-in.) hole in ametal panel placed directly under the tube. Place a containerunder the hole in the panel and allow a weighed amount of sandto pass through the tube onto the panel. Weigh the amou
29、nt ofsand that passed through the hole into the container. Theapparatus can be considered to be in calibration if the amountof sand that passed through the hole is 90 to 93 % of theamount of sand that impinged on the panel.9. Conditioning9.1 Unless otherwise agreed upon between purchaser andseller,
30、condition the coated test panels for at least 24 h at 23 62C and 50 6 5 % relative humidity. Conduct the test in thesame environment or immediately on removal.10. Procedure10.1 Mark off on each coated panel three circular areas,each approximately 1 in. (25 mm) in diameter, and so arrangedthat each c
31、an be properly positioned in the panel support of theabrasion tester. Measure the thickness of the coating by TestMethods D1005, D1186,orD1400 in at least three locations ineach area. Record the mean of each set of measurements as thethickness of the coating over the respective area.10.2 After condi
32、tioning, secure the coated panel in the testeras described in 6.1. Adjust the panel so that one of the markedareas will be centered under the guide tube. Pour standard sand,measured volumetrically, into the funnel. Withdraw the gateand allow the sand to flow through the guide tube and impingeon the
33、coated panel. Collect the sand in a container located atthe bottom of the tester. Repeat this operation until a 4-mm(532-in.) diameter area of the coating has worn through to thesubstrate.Aconvenient increment of sand to employ during thetest is 2000 6 10 mL. As the end-point is approached,increment
34、s of 200 6 2 mL may be introduced into the funnel.NOTE 4When the gate is withdrawn from the guide tube, make certainthat a collar covers the slit opening in the tube.10.3 Abrade each of the remaining marked-off areas of thecoated panel as outlined in 10.2.NOTE 5Check the alignment of the guide tube
35、at frequent intervals toensure that the concentrated inner core of the sand stream is falling in thecenter of the flow.NOTE 6After 25 passes through the apparatus, resieve the sand witha No. 30 sieve to remove fines. Replace the sand after 50 passes.10.4 Repeat 10.1-10.3 on at least one additional p
36、anelcoated with the material under test.11. Calculation11.1 For each area of the coated panel tested, calculate theabrasion resistance, A, in litres per mil from the followingequation:A 5 V/T (1)where:V = volume of abrasive used, L (to one decimal place) andT = thickness of coating, mils (to one dec
37、imal place).11.2 Calculate the mean of the abrasion resistance valuesobtained for different areas of the coated panel and the meanvalue of the replicate panels.12. Report12.1 Report the following information for each coated paneltested:12.1.1 Temperature and humidity during curing and at thetime of
38、testing,12.1.2 Type and source of abrasive,12.1.3 Litres of abrasive used for each area tested,12.1.4 Coating thickness in mils for each area tested,12.1.5 Abrasion resistance values for each area tested,12.1.6 Mean abrasion resistance for each coated paneltested, and12.1.7 Mean abrasion resistance
39、and range of the replicatecoated panels.13. Precision713.1 On the basis of an interlaboratory test of this testmethod in which three laboratories tested four types of coatingsdiffering in their abrasion resistance, the within-laboratorycoefficient of variation was found to be 9 % with 22 df and theb
40、etween-laboratories coefficient of variation 35 % with 7 df.Based on these coefficients, the following criteria should beused for judging the acceptability of results at the 95 %confidence level.13.1.1 RepeatabilityTwo results, each the mean of threeruns, obtained by the same operator should be cons
41、ideredsuspect if they differ by more than 25 % of their mean value.13.1.2 ReproducibilityTwo results, each the mean of threeruns, obtained by operators in different laboratories should beconsidered suspect if they differ by more than 118 % of theirmean value.NOTE 7The reproducibility of this test is
42、 improved substantially whenrankings of the coatings by magnitude of abrasion resistance are used. Inthe interlaboratory test for evaluating precision, all laboratories ranked thecoatings in the same order.13.2 BiasAt the time of the study, there was no acceptedreference material suitable for determ
43、ining bias for this testmethod, therefore no statement on bias is being made.METHOD BFALLING SILICON CARBIDE TEST14. Apparatus and Materials14.1 Abrasion Tester, as described in 6.1, with two excep-tions:14.1.1 A metal washer with an opening of 8.5 6 0.1 mm iscentered in the bottom opening of the fu
44、nnel to restrict the flowof the abrasive.7Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D01-1037.D968 05 (2010)314.1.2 The disk gate installed in a slit at the top of the guidetube may be replaced by a gate in the bottom of the
45、 funnel. Thisgate consists of a solid metal disk attached to a long verticalscrew and mounted above the washer.14.2 Standard AbrasiveSilicon carbide grain shall beconsidered standard when graded as follows after 5 min ofcontinuous sieving:0 % retained on a No. 10 (2.00 mm) sieve Maximum of 20 % reta
46、ined on a No. 14 (1.40 mm) sieveMinimum of 45 % retained on a No. 16 (1.18 mm) sieveMinimum of 70 % retained on a No. 16 (1.18 mm) and No. 18(1.00 mm) sieve3 % Maximum passes a No. 20 (850 m) sieve Corrected editorially.These grading requirements correspond to No. 16 grit inaccordance with ANSI B74.
47、122001. These grading require-ments also correspond to F16 grit in accordance with 42-GB-1984-R1993 FEPAStandard.14.2.1 Use the sieves described in Specification E11.15. Test Specimens15.1 Prepare the coated panels as outlined in 7.1 and 7.2.16. Standardization16.1 Standardize the abrasion tester by
48、 the procedures givenin 8.1 and 8.2, with the following exceptions:16.1.1 Use silicon carbide where sand is specified.16.1.2 Weigh the volume of silicon carbide to be introducedinto the tester. Determine the efflux time for this volume. Therate of flow shall be 10 61 g/s.17. Conditioning17.1 Unless
49、otherwise agreed upon between purchaser andseller, condition the coated panels for at least 24 h at 23 6 2Cand 50 6 5 % relative humidity. Conduct the test in the sameenvironment or immediately on removal therefrom.18. Procedure18.1 Measure the thickness of the coating by the proceduresgiven in 10.1.18.2 Abrade the coated panel by the procedures given in10.2 and 10.3 using silicon carbide as the abrasive. Determinethe volume or weight, or both, of abrasive used to reach the endpoint.18.3 Repeat 18.1 and 18.2 on at least one additional coated
