1、Designation: D968 16D968 17Standard 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 year of la
2、st 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 U.S. Department of Defense.1. Scope*1.1 These test methods cover the dete
3、rmination of the resistance of organic coatings to abrasion produced by abrasive fallingonto coatings applied to a plane rigid surface, such as a metal or glass panel.1.2 Two test methods based on different abrasives are covered as follows:SectionsMethod AFalling Sand Abrasion Test 6 13Method BFalli
4、ng Silicon Carbide Abrasion Test 14 211.3 These methods should be restricted to testing in only one laboratory when numerical values are used because of the poorreproducibility of the methods (see 13.1.2 and 21.1.2). Interlaboratory agreement is improved significantly when ranking is usedin place of
5、 numerical values.1.4 The values stated in SI units are to be regarded as the standard with the exception of mils when determining coatingthickness. The values given in parentheses are for information only.1.5 This standard does not purport to address the safety concerns, if any, associated with its
6、 use. It is the responsibility of theuser of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitationsprior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardizat
7、ionestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D823 Practices for Producing Films of Uniform Thickness
8、 of Paint, Varnish, and Related Products on Test PanelsD1005 Test Method for Measurement of Dry-Film Thickness of Organic Coatings Using MicrometersD7091 Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metalsand Nonmagnetic, Nonconductive Coat
9、ings Applied to Non-Ferrous MetalsE11 Specification for Woven Wire Test Sieve Cloth and Test Sieves2.2 Other Standards:ANSI B74.12 Specifications for the Size of Abrasive Grain Grinding Wheels, Polishing and General Industrial Uses3FEPA Standard 42-2:2006 Grains of Fused Aluminum Oxide, Silicon Carb
10、ide and other Abrasive Materials for BondedAbrasives and for General Applications Microgrits F230 to F200043. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 abrasion resistance, nthe amount of abrasive required to wear through a unit film thickness of the coating.1 These test me
11、thods are under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and are the direct responsibility ofSubcommittee D01.23 on Physical Properties of Applied Paint Films.Current edition approved Dec. 1, 2016June 1, 2017. Published January 2017June 2017.
12、Originally approved in 1948. Last previous edition approved in 2015 as D968 15.DOI: 10.1520/D0968-16.10.1520/D0968-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to
13、 the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.4 Available from Federation of European Producers of Abrasives (FEPA), 20 av., Reille, Paris, F-75014, www.fepa-.T
14、his document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior edit
15、ions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959
16、. United States14. Summary of Test Method4.1 Abrasive is allowed to fall from a specified height through a guide tube onto a coated panel until the substrate becomesvisible. The amount of abrasive per unit film thickness is reported as the abrasion resistance of the coating on the panel. Silica sand
17、or silicon carbide may be used, as specified.5. Significance and Use5.1 Silica sand produces a slower rate of abrasion for organic coatings than that provided by silicon carbide. For some typesof coatings, it may also provide greater differentiation.5.2 The abrasion resistance scales produced by the
18、 two methods differ, but the methods provide approximately the samerankings of coatings for abrasion resistance.5.3 Each of the methods has been found useful for rating the abrasion resistance of specific types of coatings. For exampleMethod A (falling sand) has been used for rating floor coatings w
19、hile Method B (falling silicon carbide) has been used for ratingcoatings for ship decks.METHOD AFALLING SAND ABRASION TEST 56. Apparatus and Materials6.1 Abrasion Tester, as illustrated in Fig. 1 and Fig. 2.Agate for starting the flow of abrasive is located near the top of the guidetube. It consists
20、 of a metal disk inserted into a slit in the side of the guide tube with a collar covering the slit. The guide tube shallbe firmly supported in a vertical position over a suitable receptacle, which shall contain a support for holding the coated panel atan angle of 45 to the vertical. The opening of
21、the tube is directly above the area to be abraded and the distance from the tube tothe coated surface face at the nearest point is 25 mm (1 in.) when measured in the vertical direction. The base of the apparatusshall be fitted with adjusting screws for properly aligning the equipment.5 Hipkins, C. C
22、., and Phain, R. J., “The Falling Sand Abrasion Tester,” ASTM Bulletin, No. 143, December 1946, pp. 1822.FIG. 1 Apparatus for Falling Sand Abrasion TestD968 1726.2 Standard AbrasiveNatural silica sand from the St. Peters or Jordan sandstone deposits (located in the central UnitedStates) shall be con
23、sidered standard when graded as follows after 5 min of continuous sieving. Use the sieves described inSpecification E11.0 % retained on a No. 16 (1.18 mm) sieveMaximum 15 % retained on a No. 20 (850 m) sieveMinimum 80 % retained on a No. 30 (600 m) sieveMaximum 5 % passing a No. 30 (600 m) sieveThe
24、sand is characterized by its grain shape and has a silicon dioxide content greater than 99 %.NOTE 1The abrading qualities of sand obtained from different sources may differ slightly even though the sand meets the sieve requirements.Therefore, for maximum precision of test results, purchaser and sell
25、er should use sand from the same source.7. Test Specimens7.1 Apply uniform coatings of the material to be tested to a plane, rigid 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 humidity and temperatur
26、e agreed upon between the purchaser and seller.NOTE 2The coatings should be applied in accordance with Practices D823, or as agreed upon between the purchaser and the seller.NOTE 3The thickness of the dry coatings should be measured in accordance with Test Methods D1005 or D7091.NOTE 4While the mini
27、mum of two coated panels is acceptable, evaluating three or more panels per material will provide greater confidence in yourtest results.8. Standardization8.1 Pour a quantity of standard sand into the funnel and examine the sand stream falling from the lower end of the guide tube.Align the apparatus
28、 by means of the adjusting screws in the base until the inner concentrated core of the sand stream falls in thecenter of the flow when viewed at two positions at 90 to each other. Introduce a measured volume of sand (2000 6 10 mL is aconvenient amount) and determine the time of efflux. The rate of f
29、low shall be 2 L of sand in 21 to 23.5 s.NOTE 1All dimensions are given in inches. 1 in. = 25.4 mm.FIG. 2 Design Details of Abrasion Test ApparatusD968 1738.2 Secure a trial panel in the testing position, as described in 6.1, and introduce the sand in increments until a spot 4 mm (532in.) in diamete
30、r is worn through to the base material. The overall abraded area shall be elliptical in shape, about 25 mm (1 in.) inwidth and 30 mm (114 in.) in length. The center of the area of maximum abrasion shall be on the centerline through the longeraxis of the abraded pattern and within 14 to 17 mm (916 to
31、 1116 in.) of the top edge. Slight final adjustment of the instrument maybe required to center the abrasion spot in the pattern.8.3 Afinal check on alignment is made by determining the amount of sand that passes through a 4-mm (532-in.) hole in a metalpanel placed directly under the tube. Place a co
32、ntainer under the hole in the panel and allow a weighed amount of sand to passthrough the tube onto the panel. Weigh the amount of sand that passed through the hole into the container. The apparatus can beconsidered to be in calibration if the amount of sand that passed through the hole is 90 to 93
33、% of the amount of sand that impingedon the panel.9. Conditioning9.1 Unless otherwise agreed upon between purchaser and seller, condition the coated test panels for at least 24 h at 23 6 2Cand 50 6 5 % relative humidity. Conduct the test in the same environment or immediately on removal therefrom.10
34、. Procedure10.1 On each coated panel mark three circular areas, each approximately 25 mm (1 in.) in diameter, and so arranged that eachcan be properly positioned in the panel support of the abrasion tester. Measure the thickness of the coating by Test Methods D1005or D7091 in at least three location
35、s in each area. Record the mean of each set of measurements as the thickness of the coating overthe respective area.10.2 After conditioning, secure the coated panel in the tester as described in 6.1.Adjust the panel so that one of the marked areaswill be centered under the guide tube.10.3 Pour stand
36、ard sand, measured volumetrically, into the funnel. Withdraw the gate and allow the sand to flow through theguide tube and impinge on the coated panel. Collect the sand in a container located at the bottom of the tester. Repeat this operationuntil a 4-mm (532-in.) diameter area of the coating has wo
37、rn through to the substrate. A convenient increment of sand to employduring the test is 2000 6 10 mL. As the end-point is approached, increments of 200 6 2 mL may be introduced into the funnel.NOTE 5When the gate is withdrawn from the guide tube, make certain that a collar covers the slit opening in
38、 the tube.10.4 Abrade each of the remaining marked-off areas of the coated panel as outlined in 10.2.NOTE 6Check the alignment of the guide tube at frequent intervals to ensure that the concentrated inner core of the sand stream is falling in the centerof the flow.NOTE 7After 25 passes through the a
39、pparatus, resieve the sand with a No. 30 sieve to remove fines. Replace the sand after 50 passes.NOTE 8Sand should be stored in a humidity controlled environment. Excessive moisture level of the sand may influence the results and can becorrected by drying the sand for 1 h in an oven at approximately
40、 82C (180F).10.5 Repeat 10.1 10.4 on at least one additional panel coated with the material under test.11. Calculation11.1 For each area of the coated panel tested, calculate the abrasion resistance, A, in litres per mil from the following equation:Avolume 5V/T (1)where:V = volume of abrasive used,
41、L (to one decimal place) andT = thickness of coating, mils (to one decimal place).11.2 Calculate the mean of the abrasion resistance values obtained for different areas of the coated panel and the mean valueof the replicate panels.12. Report12.1 Report the following information for each coated panel
42、 tested:12.1.1 Temperature and humidity during curing and at the time of testing,12.1.2 Type and source of abrasive,12.1.3 Litres of abrasive used for each area tested,12.1.4 Wear pattern measurements, if different than 8.2,12.1.5 Coating thickness in mils for each area tested,12.1.6 Abrasion resist
43、ance values for each area tested,12.1.7 Mean abrasion resistance for each coated panel tested, and12.1.8 Mean abrasion resistance and range of the replicate coated panels.D968 17413. Precision 613.1 On the basis of an interlaboratory test of this test method in which three laboratories tested four t
44、ypes of coatings differingin their abrasion resistance, the within-laboratory coefficient of variation was found to be 9 % with 22 df and thebetween-laboratories coefficient of variation 35 % with 7 df. Based on these coefficients, the following criteria should be used forjudging the acceptability o
45、f results at the 95 % confidence level.13.1.1 RepeatabilityTwo results, each the mean of three runs, obtained by the same operator should be considered suspect ifthey differ by more than 25 % of their mean value.13.1.2 ReproducibilityTwo results, each the mean of three runs, obtained by operators in
46、 different laboratories should beconsidered suspect if they differ by more than 118 % of their mean value.NOTE 9The reproducibility of this test is improved substantially when rankings of the coatings by magnitude of abrasion resistance are used. In theinterlaboratory test for evaluating precision,
47、all laboratories ranked the coatings in the same order.13.2 BiasAt the time of the study, there was no accepted reference material suitable for determining bias for this test method,therefore no statement on bias is being made.METHOD BFALLING SILICON CARBIDE TEST14. Apparatus and Materials14.1 Abras
48、ion Tester, as described in 6.1, with two exceptions:14.1.1 A metal washer with an opening of 8.5 6 0.1 mm is centered in the bottom opening of the funnel to restrict the flowof the abrasive.14.1.2 The disk gate installed in a slit at the top of the guide tube may be replaced by a gate in the bottom
49、 of the funnel. Thisgate consists of a solid metal disk attached to a long vertical screw and mounted above the washer.14.2 Standard AbrasiveSilicon carbide grain shall be considered standard when graded as follows after 5 min of continuoussieving:0 % retained on a No. 10 (2.00 mm) sieveMaximum of 20 % retained 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) sieveThese grading requ
