1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.Copyright 2002 Society of Automotive Engineers, Inc.All rights reserved. No part of this
3、 publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying,recording, or otherwise, without the prior written permission of SAE.TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (o
4、utside USA)Fax: 724-776-0790Email: custsvcsae.orgSAE WEB ADDRESS: http:/www.sae.orgSURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICEJ400REV.NOV2002Issued 1968-07Revised 2002-11Superseding J400 DEC2001Test for Chip Resistance of Surface Coatings1. ScopeThis SAE Recomm
5、ended Practice covers a laboratory procedure for testing and evaluating theresistance of surface coating to chipping by gravel impact. The test is designed to reproduce the effect ofgravel or other media striking exposed paint or coated surfaces of an automobile and has been correlated withactual fi
6、eld results. The specific intent of the test is to evaluate organic surface coatings or systems on flat testpanels; however, It may be possible to extend this type of testing to finished parts or other types of materialssuch as anodized aluminum or plated plastics if the results are interpreted with
7、 respect to the limitations andintent implied by the original testing procedures and rating system.This document may involve hazardous materials, operations, and equipment. This document does not purportto address all of the safety problems associated with its use. It is the responsibility of whoeve
8、r uses thisdocument to consult and establish safety and health practices and determine the applicability of regulatorylimitations prior to use.All dimensions are nominal unless otherwise noted.2. Reference2.1 Related PublicationThe following publication is provided for information purposes only and
9、is not arequired part of this document.2.1.1 GENERAL MOTORS PUBLICATIONAvailable from GM AC Rochester/GMC, P.O. 1360, Flint, MI 48501-8054.GMR-767The Measurements of Chipping of Automotive Finishes, Hays, Donald R., Detroit, MI,General Motors Laboratories, 1968SAE J400 Revised NOV2002-2-3. Summary o
10、f MethodThe test consists of projecting standardized road gravel by means of a controlled airblast onto a suitable test panel. The testing apparatus is called a gravelometer, designed to contain roadgravel, a test panel holder, and a gravel projecting mechanism. The projecting mechanism, located in
11、front ofthe test panel, consists of an air nozzle in the base of an inverted pipe tee. The stem of the pipe tee pointsupward and is located beneath a vibrating hopper into which the gravel is poured. The gravel, falling into theair blast, is projected toward and impacts upon the test panel, which is
12、 usually held perpendicular to theimpinging gravel. All testing is conducted under controlled temperature conditions, generally roomtemperature (ambient) or 29 C 3 C (20 F 5 F). After the gravel impact, tape is applied to remove anyloose paint chips remaining on the panel, and the degree of chipping
13、 is determined by visual comparison withthe SAE Chipping Rating Standards1, by counting the number and sizes of all chips, or by other methodsdeemed suitable between the contractual parties involved.4. Equipment and Materials4.1 GravelometerA gravel projecting test apparatus which is constructed acc
14、ording to the design specificationsshown in Figure 1.FIGURE 1TEST APPARATUS1. Available from Society of Automotive Engineers, Inc., 400 Commonwealth Drive, Warrendale, PA 15096-0001Identified as EA-400.SAE J400 Revised NOV2002-3-4.1.1 OPERATION/M AINTENANCE CHECKLISTThe operation/maintenance checkli
15、st shown in Figure 2 shall becompleted at least once a month for testers that are operated on a weekly basis and once every 6 months fortesters that are operated less frequently.NOTE Values in chart are specific to the standard gravel testing protocol. Different specifications may benecessary for ot
16、her media types.If the answer to any of the following questions is NO, discontinue testing until the problem has beencorrected.FIGURE 2CHECKLISTSAE J400 Revised NOV2002-4-4.2 Gravel The gravel for this test shall be water-worn road gravel, not crushed limestone or rock. The gravelwill pass through 1
17、5.86 mm (5/8 in) space screen when graded, but be retained on 9.53 mm (3/8 in) spacescreen. It is important to note that mesh screen is not a substitute for space screen. The gravelometer has9.53 mm (3/8 in) space screen in the bottom to separate fractured pieces of rock and dust smaller than 9.53mm
18、 (3/8 in) so that the retained gravel on this screen may be reused. Because the gravel tends to blunt orfragment after repeated impacts, it should be changed at a regular frequency. For testers that are operated ona weekly basis, 2 pints of gravel shall be replaced with fresh gravel each month. For
19、testers that are operatedon less frequent basis, 2 pints of gravel shall be replaced with fresh gravel at least every 6 months.Gravel must be washed prior to initial use.Other media may be used as agreed upon by contractual parties.NOTE Pint measurements refer to a 1 pint container full to the top.4
20、.3 Paint Removal Tape10 cm (4 in) wide or 5 cm (2 in) wide, 3M product #898 filament strapping tape orequivalent. Other tape may be used as agreed upon by contractual parties.NOTE The adhesion strength of the tape use makes a significant impact on how much separated paint isremoved. 4.4 Temperature
21、Conditioning EquipmentGravelometer tests are usually run at ambient or a lowertemperature, generally 29 C (20 F), which shall be mutually agreed upon by contractual parties. Testsconducted at different temperatures will employ the following:4.4.1 METHOD AA cold room or chamber in which the gravelome
22、ter and test panels are maintained at thespecified temperature of testing.For freezers that employ a defrosting mechanism, document the method of defrosting and any temperaturechanges.4.4.2 METHOD BA freezer in which the test panels are cooled to 5.6 C (10 F) below the test temperature beforethey ar
23、e individually transferred and tested immediately in a gravelometer at room temperature locatednearby.4.4.3 METHOD CAmbient: room maintained at a temperature between 20 C (68 F) and 30 C (86 F).4.5 Transparent GridA chip counting aid constructed of transparent plastic approximately 3.2 mm x 12.7 cm(
24、1/8 x 5 x 5 in), on which a 10.16 x 10.16 cm (4 x 4 in) grid of 2.54 cm (1 in) squares has been etched orscribed.4.6 Chipping Rating StandardsA photographic transparency, depicting the size and shape of each chip. SeeFigure 3 for representation of this transparency. Figure 3 IS A REPRESENTATION ONLY
25、.SAE J400 Revised NOV2002-5-FIGURE 3CHIPPING RATING STANDARDS (REPRESENTATION ONLY)SAE J400 Revised NOV2002-6-4.7 Test SpecimensIt is recommended that three replicates of each test specimen be exposed in thegravelometer. The number of replicates will be agreed upon between contractual parties. The t
26、est specimensare typically flat and 10.16 x 30.48 cm (4 x 12 in) in size in order to fit into the panel holder of the gravelometer.The test panel material, the panels thickness or gauge, and preliminary surface treatments (such asphosphating or anodizing) should be the same for all tests in any seri
27、es and as representative as possible ofthe actual part. Any deviations in these parameters may produce misleading test results.For profiled test specimens, or nonstandard test specimens, limits for uniform thickness, uniform backing, anduniform specimen holders must be determined and agreed upon by
28、contractual parties.5. Setup and Procedures5.1 Setup5.1.1 Paint or process the test panels as specified for the systems under test.It should be noted that the chipping test results will be dependent upon the nature of the coatingsformulation, the method and degree of drying or curing of the various
29、coats, and the film thickness involved.Uniformity of film thickness is extremely important, and each component of the system should be controlledas uniformly as possible.5.1.2 The test specimens must reach the test temperature for a minimum of 15 minutes prior to testing inaccordance with the approp
30、riate method specified in 4.5.In the conditioning environment, proper heat transfer can be facilitated by separating the test specimens sothat the conditioned air can circulate freely about the specimen.5.1.3 Fill a 0.473 L (1 pt) container to the top with grated/screened gravel. During exposure of
31、multiple specimens, no more than 10 pt of gravel shall be allowed to collect on the sizingscreen. Once 10 pt have collected on the screen, scrape the gravel across the screen so that the smallrocks will fall beneath the screen. Remove the gravel that remains on top of the screen from thegravelometer
32、 for re-use. Remove and discard any stones that have lodged in the screen. 5.1.4 Other media can be used as agreed upon by contractual parties.5.1.5 Adjust air pressure on the gravelometer to 483 kPa 21 kPa (70 psi 3 psi) with the air valve open.For older cabinet type gravelometers, keep lid to grav
33、el chamber on the gravelometer closed during thisoperation as safety precaution.5.1.6 Set feed rate so that the hopper empties in 7 to 10 s/pt.5.1.7 Other air pressures can be used as agreed upon by contractual parties.SAE J400 Revised NOV2002-7-5.2 Procedure5.2.1 OLD CABINET T YPE GRAVELOMETERa. Af
34、ter the air pressure is adjusted, shut off air valve, and open the lid to the specimen chamber. Placeone test specimen conditioned at the desired test temperature in the panel holder with the coated sidefacing the gravel projecting mechanism. Mount the specimen as tightly as possible so as not to af
35、fectthe angle of the panel orientation or allow movement during the test. b. The specimen holder shall have an edge-supported backer plate. Other specimen mounting fixturesmay be used as agreed upon by contractual parties.c. Close lid to panel chamber.d. Open the gravel feed door and pour gravel fro
36、m the one pint container obtained from step 5.1.3 intothe top of the gravel hopper. Do not allow gravel to fall into the nozzle entrance. Open the air valve toallow the air to project the gravel at the sample.NOTE 1The gravel hopper must empty within 7 to 10 s. If gravel remains in the hopper after
37、10 s, stop thetest and investigate the cause. The operator may not touch the gravel during the test or otherwisephysically help the gravel into the funnel.NOTE 2It is important to note that the vibrator may become frozen when the chamber is installed in a coldroom or freezer. If the vibrator is froz
38、en, discontinue the test until the vibrator has thawed and isoperating correctly.NOTE 3Shut off air valve, open lid to specimen chamber, and remove the test specimen.5.2.2 MODULAR GRAVELOMETER WITH ELECTRONIC F EED MECHANISMa. Pull back on the specimen mounting clamp to open the specimen holder on t
39、he specimen holderassembly.b. Clamp to close the specimen holder.c. Pour gravel from the one pint container obtained from step 5.1.3 into hopper.d. Set the Test Timer.5.2.3 There are two ways to operate a test on these units. A Timed Test is a test that shuts off the machine afterthe preset amount o
40、f time has passed. A Manual Test requires the operator to shut off the machine after thedesired amount of time has passed.5.2.3.1 Timed Testa. Make sure the control switch is set to STOP.b. Set the Test Timer to the desired test time. This is typically 2505 2549SAE J400 Revised NOV2002-9-6.2.2 SIZE
41、OF CHIPSThe size of the chip is specified by a rating letter selected from A-D in Table 2. Due to theirregular nature of chipping, the size cannot always be measured exactly so it has to be approximated.6.2.3 POINT OF F AILUREThe coating layer at which the most predominant chipping failure occurs is
42、 designated asthe point of failure. The notations in Table 3 can be used to designate this information if desired. Othernotations may be used with agreement between contractual parties.6.3 Details of Method I and Method II6.3.1 METHOD IEXACT COUNTING P ROCEDURE6.3.1.1 Counting can be facilitated by
43、the use of a transparent overlay onto which has been etched a grid of2.54cm (1 in) squares. The grid is placed over the area to be treated as a guide to remembering the areasthat have been counted.6.3.1.2 The operator examines the area within a 2.54 x 2.54 cm (1 x 1 in) square, decides on the size o
44、f each chipas encountered, and records it. Rate all 16 squares and record the results.6.3.1.3 The actual number of chips counted for each size is then converted into the number-letter combinationsutilizing Tables 1 and 2. The number-letter rating is then arranged with the most numerous size first,fo
45、llowed by the next more numerous, etc. This may then be followed by the Point of Failure notation.For example, for a panel on which there are 20 chips less than 1 mm (A size), 40 chips of 1 to 3 mm (Bsize), and 3 chips of 3 to 6 mm (C size) with primer-topcoat failure, the number of chips on the rat
46、ing wouldbe 5B-6A-8C (P/T). This rating can be condensed by converting the total number of chips on the panel tothe corresponding number category, which is then followed by the size designations in the same order. Inthis example, with a total of 63 chips, the rating would be summarized as 4 BAC (P/T
47、).6.3.2 METHOD IIVISUAL COMPARISON P ROCEDUREThe Chipping Rating Standards shown in Figure 3 areutilized.These have been prepared so the chips of only 1 size are shown in each illustration. The number of chipsillustrated in each standard is the fewest number of chips in each rating number category;
48、for example, theNo. 5 standards all show 25 chips, the No. 3 standards show 75 chips. All of the No. 8 and No. 10 categoriesand the lower number D size categories have not been included in order to keep the photographs to amanageable number.TABLE 2SIZE CATEGORIES FOR CHIP RATINGRating Letter Size of
49、 ChipsA 1 mm (approximately 0.03 in)B 13 mm (approximately 0.030.12 in)C 36 mm (approximately 0.120.25 in)D 6 mm (approximately 0.25 in)TABLE 3POINT OF FAILURE NOTATIONNotation Level of Failure Failure Type(S/P) Substrate to Primer Adhesional(S/T) Substrate to Topcoat Adhesional(P) Prime Cohesional(P/T) Primer to Topcoat Adhesional(T) Topcoat CohesionalSAE J400 Revised NOV2002-10-6.3.2.1 Visually compare the area to be rated with the standards.Since each standard exhibits only one chip and actual chipping seldom occurs in only
