1、Designation: D7893 13Standard Guide forCorrosion Test Panel Preparation, Testing, and Rating ofCoil-Coated Building Products1This standard is issued under the fixed designation D7893; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the 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.1. Scope1.1 This guide has been written specifically for coil-coatedmetal building products.1.2 This guide applies to
3、 preparation, testing, and rating ofline-coated and laboratory-coated test panels for the purpose ofcomparing and ranking the panels for corrosion resistance andother related properties.1.3 Testing may include accelerated laboratory corrosiontests and outdoor exposure tests.1.4 The values stated in
4、SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 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 healt
5、h practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusD610 Practice for Evaluating Degree of Rusting on PaintedSteel SurfacesD714 Test Method for Evaluating Degree of Bliste
6、ring ofPaintsD870 Practice for Testing Water Resistance of CoatingsUsing Water ImmersionD1654 Test Method for Evaluation of Painted or CoatedSpecimens Subjected to Corrosive EnvironmentsD1735 Practice for Testing Water Resistance of CoatingsUsing Water Fog ApparatusD2247 Practice for Testing Water R
7、esistance of Coatings in100 % Relative HumidityD2803 Guide for Testing Filiform Corrosion Resistance ofOrganic Coatings on MetalD3359 Test Methods for Measuring Adhesion by Tape TestD4138 Practices for Measurement of Dry Film Thickness ofProtective Coating Systems by Destructive, Cross-Sectioning Me
8、ansD4585 Practice for Testing Water Resistance of CoatingsUsing Controlled CondensationD5796 Test Method for Measurement of Dry Film Thicknessof Thin-Film Coil-Coated Systems by Destructive MeansUsing a Boring DeviceD5894 Practice for Cyclic Salt Fog/UV Exposure of PaintedMetal, (Alternating Exposur
9、es in a Fog/Dry Cabinet and aUV/Condensation Cabinet)D7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic, Nonconductive Coat-ings Applied to Non-Ferrous MetalsG7 Practice for Atmospheric Environmental Exposure Test-ing o
10、f Nonmetallic MaterialsG85 Practice for Modified Salt Spray (Fog) TestingG87 Practice for Conducting Moist SO2TestsG169 Guide for Application of Basic Statistical Methods toWeathering Tests2.2 SAE Standards:3J2334 Laboratory Cyclic Corrosion Test3. Terminology3.1 Definitions:3.1.1 test panel, na rep
11、resentative specimen of metalsubstrate, coated with a coating system for evaluation, andprepared in a way that allows measurement of environmentaldegradation, especially corrosion, for system performancecomparisons and ranking.4. Summary of Guide4.1 Test panels may be collected from coil line clips
12、andformed building panels, or may be laboratory-prepared.1This guide is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.53 on Coil Coated Metal.Current edition approved Nov. 1, 2013. Published
13、November 2013. DOI:10.1520/D7893-13.2For referenced ASTM standards, visit 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.3Available from SAE Inter
14、national (SAE), 400 Commonwealth Dr., Warrendale,PA 15096-0001, http:/www.sae.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 Test panels are prepared for testing in a specific con-figuration that simulates conditions on build
15、ings.4.3 Test panels are exposed to specific conditions in accor-dance with standard practices and methods.4.4 After testing, corrosion is measured in a way that relatesto building performance and allows performance rankingamong samples, for example, by the corrosion creep distancefrom test panel ed
16、ges.5. Significance and Use5.1 Coil-coated metals are subjected to a wide range ofenvironmental stresses. Corrosion at cut edges, damage points,and fabricated areas can occur and lead to premature failure.Proper preparation and rating of test panels produces meaning-ful test results that allows comp
17、arisons between metal sub-strates and their pretreatments as well as between coatingsystems.5.2 Laboratory-prepared test panels give a relative compari-son of the substrates and coating systems under test, but maynot duplicate all of the stresses imposed on manufacturedcomponents. Validation of resu
18、lts on a manufactured product isrecommended.5.3 Laboratory accelerated corrosion testing is useful inevaluating relative performance of new and existing metalcoatings, pretreatments, and paints. It is up to the participatingparties to agree on the significance of these tests to actual use.6. Test Pa
19、nel Preparation6.1 An experiment is planned to evaluate the effects ofspecific variables in the coated metal system on corrosionperformance. These variables typically include metal substrate,cleaning, pretreatment, primer, topcoat, forming, and otherappropriate stresses.6.2 The number of replicates
20、in a test is determined byavailability of substrate, time, resource constraints, and statis-tical methods for data analysis. Statistical methods require anumber of replicates which is dependent upon the variability ofthe system under test and the measurement system itself.Although not specific to co
21、rrosion testing, Guide G169 canserve as a reference for using statistical methods. Because oftest variations, a thorough experimental plan includes controlsto rank results. Positive (known good performance) and nega-tive (known poor performance) controls may be included formore effective data interp
22、retation.6.3 The test panel size, configuration, and features (shape,bends, scribe lines, etc.) are factors in any corrosion test andshould be determined during planning in order to ensureenough coated metal is available. A typical flat exposure testpanel might be 10 by 20 cm, but could vary to acco
23、mmodateother configurations. The anticipated corrosion creep distancewould also influence test panel size.6.4 The test panel configuration and features are chosen tosimulate real building panels. These might include cut edges,lap edges, scribe lines (to simulate damage), holes with orwithout fastene
24、rs, tension bends, impact dimples, and otherforming operations (see Fig. A1.1).6.5 In addition to test panel configuration, the laboratoryaccelerated corrosion tests, exposure sites, and panel orienta-tions should be considered. Exposure sites represent uniqueenvironments that cyclically expose the
25、test panels to manyconditions such as temperature variation, moisture, saltconcentrations, industrial pollutants, and solar radiation. Expo-sure angles such as 1, 5, and 45 from horizontal might bechosen for roof simulation, while vertical exposures would beused for side walls. Exposure directions,
26、north, south, east, orwest, can be chosen as can the degree of shade or shelter. Asheltered exposure may offer increased time of wetness for testpanels.6.6 Use of coil line-coated test panels (line clips) is pre-ferred to best represent the commercial products performance.Often, however, where a num
27、ber of variables are tested in ascreening experiment, it is not practical or economical to testline clips. In such cases, laboratory test panels may beprepared. For laboratory-prepared test panels, heating rate andpeak metal temperature should be as close as possible to coilline conditions.6.7 Pretr
28、eatments are applied to a cleaned surface byimmersion, spray, drawdown, or rollcoater as appropriate inaccordance with manufacturer specification.6.8 For laboratory-prepared test panels, coil primers andtopcoats are typically applied to test panels by wire wound rod.The wire number selected is criti
29、cal for dry film thickness(DFT) accuracy. DFT must be established for each coating/rodnumber combination because the same rod can produce differ-ent DFTs with different coatings. Typical methods for measur-ing the dry film thickness of coil coatings include PracticesD4138, D7091, and Test Method D57
30、96.6.9 For laboratory-prepared test panels, when the backsidehas not been line-primed or backed, a backer coating should beapplied to test panels. This may be accomplished with roomtemperature-cured coatings or tape.6.10 The metal shear selection is important for consistentresults and should be used
31、 consistently for all corrosion testpanels to be compared in an experiment if edge corrosion is tobe measured. The shear type and blade sharpness may influ-ence corrosion results.6.11 For tests requiring cut edge corrosion measurement,care should be taken to ensure that edges are free of excesscoati
32、ng from the front or backside and to shear the edges withthe burrs in a predetermined direction. For example, the rightedge may be sheared burr-up and the left edge burr-down. Testpanels for a given experiment must be sheared on the sameshear to ensure consistent results. Shear sharpness and gap may
33、influence results.6.12 Holes, drilled or punched, and fasteners may be used ifagreed upon between producer and user. For tests requiring apunched hole, the hole is typically punched with the burr down.Punch sharpness may also influence results.6.13 Test panels requiring a scribe may be scribed consi
34、s-tently using a carbide steel tip pencil-type scribe and metalruler to give a straight scribe line of equal length on all testpanels. Other scribing tools may also be used as agreed uponD7893 132between producer and user. Scribing may be done manually orby machine for improved consistency. A prefer
35、red scribedirection is lengthwise or vertically with respect to the expo-sure orientation to allow droplets to run along the length of thescribe line. Care should be exercised to use uniform pressureand to produce scribe cuts that are free of coating and metaldebris. Consistent force should be appli
36、ed to expose a consis-tent width of metal. For multi-layer substrates (for example,galvanized steel) producer and user should agree on the depthof scribe penetration (for example, if it is to penetrate throughthe galvanizing layer to the base steel).6.14 Tension bends may be made in test panels usin
37、glaboratory roll formers. Other types of forming may includereverse impact dimples, T-bends, and bends using a bendingbrake.6.15 A testing request document with vital information isrecommended for each individual test. Accelerated testingrequest document records might indicate which specific test,wi
38、th cycle and temperature when needed, is to be performed,how long the exposure time is to be, time intervals whenchecks are to be performed, which checks (photographs ormeasurements), how test panels are to be handled upon testcompletion, and identification of the test panels.6.16 Individual test pa
39、nels should be identified in a way thatdoes not interfere with the test, and that maintains its integritythroughout the test duration. Different methods may be se-lected depending on the test. Permanent marker on a coatedsurface may work well for laboratory accelerated corrosiontesting. Outdoor expo
40、sures or laboratory testing that exposesthe test panel to UV radiation may require scribed or stampedidentification.7. Exposure of Test Panels to Corrosive Conditions7.1 Test panels are subjected to a laboratory acceleratedcorrosion test or outdoor exposure test. The test selection andduration of th
41、e test are based on a number of factors includinghistorical, customer, or vendor specifications, known correla-tions with field performance, experience, and relationshipsbetween test conditions and product exposure conditions.Typical laboratory accelerated corrosion tests used for coil-coated buildi
42、ng products include Practices B117, D870,D1735, D2247, D4585, D5894, G85, G87, Guide D2803 andothers such as automotive cyclic test, SAE J2334. Outdoorexposure tests are conducted in accordance with Practice G7.8. Test Panel Rating8.1 Test panels should be rated as soon as possible afterremoval from
43、 the test cabinet and outdoor exposure, or arecovery time can be agreed upon between producer and user.Care must be taken to avoid damage. Loose paint may beremoved by air blow-off, scraping, or taping. Specific guidanceis provided in Test Method D1654.8.2 Cut edge creep ratings are normally measure
44、d in milli-metres perpendicular from the test panel cut edge to the leadingedge of the paint delamination front. Ratings may be made atan agreed upon number of equally spaced points along the edgeand averages taken. A template is helpful to maintain spacingand consistency from test panel to test pan
45、el. The bottom andtop 10 mm of the test panel should be excluded from themeasurements.8.3 Scribe creep can be measured in various ways, soproducer and user should agree upon a method to maintainconsistency. Scribe creep is often measured perpendicular tothe scribe on both sides at the predetermined
46、number of spotsand averaged. A template is helpful to maintain consistency.The number of readings should be agreed upon betweenproducer and user and be kept consistent within a test series.8.4 Face blistering can be rated in accordance with TestMethod D714.8.5 Adhesion by tape test can be rated usin
47、g Test MethodD3359.8.6 Other ratings may also be used depending upon testpanel configuration. Corrosion at bends, punched holes, andimpact dimples are examples. Red rust may be rated using TestMethod D610.8.7 Statistical analysis of data can be applied to differentiatesystem performance from measure
48、ment variability, forexample, the Students t-test. Guide G169 can be used as areference for statistical analysis. Information developed fromsuch analysis can be used to properly rank system performancein each test. Weighting of results from various tests might bebased on historical or customer speci
49、fications, known correla-tions with field performance, experience, and relationshipsbetween test conditions and product exposure conditions.9. Report9.1 A report of results should include the test series number,substrate identification, coating mass for galvanized products,thickness, pretreatment identification, pretreatment weight,primer, primer thickness, topcoat, topcoat thickness, corrosiontest with standard method number, duration of the test and anyirregularities. Where applicable, the report should include edgecreep for burr-up and burr-down edges, lap edges, scribe creep
