1、Designation: D7893 13 (Reapproved 2018)Standard 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
2、 case of revision, 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 Thi
3、s guide applies to 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
4、 values stated in 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-priat
5、e safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopme
6、nt of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusD610 Practice for Evaluating Degree of Rusting on PaintedSteel
7、 SurfacesD714 Test Method for Evaluating Degree of Blistering 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 CoatingsUs
8、ing Water Fog ApparatusD2247 Practice for Testing Water Resistance of Coatings in100 % Relative HumidityD2803 Guide for Testing Filiform Corrosion Resistance ofOrganic Coatings on MetalD3359 Test Methods for Rating Adhesion by Tape TestD4138 Practices for Measurement of Dry Film Thickness ofProtecti
9、ve Coating Systems by Destructive, Cross-Sectioning MeansD4585 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
10、 Fog/UV Exposure of PaintedMetal, (Alternating Exposures 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 Prac
11、tice for Atmospheric Environmental Exposure Test-ing of 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 Test
12、3. Terminology3.1 Definitions:3.1.1 test panel, na representative specimen of metalsubstrate, coated with a coating system for evaluation, and1This guide is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubco
13、mmittee D01.53 on Coil Coated Metal.Current edition approved June 1, 2018. Published June 2018. Originallyapproved in 2013. Last previous edition approved in 2013 as D7893 13. DOI:10.1520/D7893-13R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servic
14、e at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from SAE International (SAE), 400 Commonwealth Dr., Warrendale,PA 15096-0001, http:/www.sae.org.Copyright ASTM International, 100 Barr Harbor Drive, P
15、O Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued
16、by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1prepared 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 andformed b
17、uilding panels, or may be laboratory-prepared.4.2 Test panels are prepared for testing in a specific con-figuration that simulates conditions on buildings.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
18、 a way that relatesto building performance and allows performance rankingamong samples, for example, by the corrosion creep distancefrom test panel edges.5. Significance and Use5.1 Coil-coated metals are subjected to a wide range ofenvironmental stresses. Corrosion at cut edges, damage points,and fa
19、bricated areas can occur and lead to premature failure.Proper preparation and rating of test panels produces meaning-ful test results that allows comparisons between metal sub-strates and their pretreatments as well as between coatingsystems.5.2 Laboratory-prepared test panels give a relative compar
20、i-son of the substrates and coating systems under test, but maynot duplicate all of the stresses imposed on manufacturedcomponents. Validation of results on a manufactured product isrecommended.5.3 Laboratory accelerated corrosion testing is useful inevaluating relative performance of new and existi
21、ng metalcoatings, pretreatments, and paints. It is up to the participatingparties to agree on the significance of these tests to actual use.6. Test Panel Preparation6.1 An experiment is planned to evaluate the effects ofspecific variables in the coated metal system on corrosionperformance. These var
22、iables typically include metal substrate,cleaning, pretreatment, primer, topcoat, forming, and otherappropriate stresses.6.2 The number of replicates in a test is determined byavailability of substrate, time, resource constraints, and statis-tical methods for data analysis. Statistical methods requi
23、re anumber of replicates which is dependent upon the variability ofthe system under test and the measurement system itself.Although not specific to corrosion testing, Guide G169 canserve as a reference for using statistical methods. Because oftest variations, a thorough experimental plan includes co
24、ntrolsto rank results. Positive (known good performance) and nega-tive (known poor performance) controls may be included formore effective data interpretation.6.3 The test panel size, configuration, and features (shape,bends, scribe lines, etc.) are factors in any corrosion test andshould be determi
25、ned 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 accommodateother configurations. The anticipated corrosion creep distancewould also influence test panel size.6.4 The test panel configuration and feature
26、s are chosen tosimulate real building panels. These might include cut edges,lap edges, scribe lines (to simulate damage), holes with orwithout fasteners, tension bends, impact dimples, and otherforming operations (see Fig. A1.1).6.5 In addition to test panel configuration, the laboratoryaccelerated
27、corrosion tests, exposure sites, and panel orienta-tions should be considered. Exposure sites represent uniqueenvironments that cyclically expose the test panels to manyconditions such as temperature variation, moisture, saltconcentrations, industrial pollutants, and solar radiation. Expo-sure angle
28、s such as 1, 5, and 45 from horizontal might bechosen for roof simulation, while vertical exposures would beused for side walls. Exposure directions, north, south, east, orwest, can be chosen as can the degree of shade or shelter. Asheltered exposure may offer increased time of wetness for testpanel
29、s.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 number of variables are tested in ascreening experiment, it is not practical or economical to testline clips. In such cases, laboratory test panels may b
30、eprepared. For laboratory-prepared test panels, heating rate andpeak metal temperature should be as close as possible to coilline conditions.6.7 Pretreatments are applied to a cleaned surface byimmersion, spray, drawdown, or rollcoater as appropriate inaccordance with manufacturer specification.6.8
31、For laboratory-prepared test panels, coil primers andtopcoats are typically applied to test panels by wire wound rod.The wire number selected is critical for dry film thickness(DFT) accuracy. DFT must be established for each coating/rodnumber combination because the same rod can produce differ-ent D
32、FTs with different coatings. Typical methods for measur-ing the dry film thickness of coil coatings include PracticesD4138, D7091, and Test Method D5796.6.9 For laboratory-prepared test panels, when the backsidehas not been line-primed or backed, a backer coating should beapplied to test panels. Thi
33、s may be accomplished with roomtemperature-cured coatings or tape.6.10 The metal shear selection is important for consistentresults and should be used consistently for all corrosion testpanels to be compared in an experiment if edge corrosion is tobe measured. The shear type and blade sharpness may
34、influ-ence corrosion results.6.11 For tests requiring cut edge corrosion measurement,care should be taken to ensure that edges are free of excesscoating 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
35、 the left edge burr-down. Testpanels for a given experiment must be sheared on the sameshear to ensure consistent results. Shear sharpness and gap mayinfluence results.D7893 13 (2018)26.12 Holes, drilled or punched, and fasteners may be used ifagreed upon between producer and user. For tests requiri
36、ng 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 consis-tently using a carbide steel tip pencil-type scribe and metalruler to give a straight scribe line of equal length on all testpanels.
37、 Other scribing tools may also be used as agreed uponbetween producer and user. Scribing may be done manually orby machine for improved consistency. A preferred scribedirection is lengthwise or vertically with respect to the expo-sure orientation to allow droplets to run along the length of thescrib
38、e line. Care should be exercised to use uniform pressureand to produce scribe cuts that are free of coating and metaldebris. Consistent force should be applied to expose a consis-tent width of metal. For multi-layer substrates (for example,galvanized steel) producer and user should agree on the dept
39、hof 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 usinglaboratory roll formers. Other types of forming may includereverse impact dimples, T-bends, and bends using a bendingbrake.6.15 A testing requ
40、est document with vital information isrecommended for each individual test. Accelerated testingrequest document records might indicate which specific test,with cycle and temperature when needed, is to be performed,how long the exposure time is to be, time intervals whenchecks are to be performed, wh
41、ich checks (photographs ormeasurements), how test panels are to be handled upon testcompletion, and identification of the test panels.6.16 Individual test panels should be identified in a way thatdoes not interfere with the test, and that maintains its integritythroughout the test duration. Differen
42、t methods may be se-lected depending on the test. Permanent marker on a coatedsurface may work well for laboratory accelerated corrosiontesting. Outdoor exposures or laboratory testing that exposesthe test panel to UV radiation may require scribed or stampedidentification.7. Exposure of Test Panels
43、to Corrosive Conditions7.1 Test panels are subjected to a laboratory acceleratedcorrosion test or outdoor exposure test. The test selection andduration of the test are based on a number of factors includinghistorical, customer, or vendor specifications, known correla-tions with field performance, ex
44、perience, and relationshipsbetween test conditions and product exposure conditions.Typical laboratory accelerated corrosion tests used for coil-coated building products include Practices B117, D870,D1735, D2247, D4585, D5894, G85, G87, Guide D2803 andothers such as automotive cyclic test, SAE J2334.
45、 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 the test cabinet and outdoor exposure, or arecovery time can be agreed upon between producer and user.Care must be taken to avoid damage. Loos
46、e 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 measured in milli-metres perpendicular from the test panel cut edge to the leadingedge of the paint delamination front. Ratings may be made atan agree
47、d upon number of equally spaced points along the edgeand averages taken. A template is helpful to maintain spacingand consistency from test panel to test panel. The bottom andtop 10 mm of the test panel should be excluded from themeasurements.8.3 Scribe creep can be measured in various ways, soprodu
48、cer and user should agree upon a method to maintainconsistency. Scribe creep is often measured perpendicular tothe scribe on both sides at the predetermined number of spotsand averaged. A template is helpful to maintain consistency.The number of readings should be agreed upon betweenproducer and use
49、r 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 using 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 measurement variability, forexample, the Students t-test. Guide G169 can be used as areference for statistical analysis. Information
