ASTM_D_6491_-_09.pdf

Designation:D649109Standard Practice forEvaluation of Aging Resistance of Prestressed PrepaintedMetal In a Dry Heat Test1This standard is issued under the fixed designation D6491;the number immediately following the designation indicates the year oforiginal adoption or,in the 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 practice can be used to evaluate the resistance of aprestressed prepainted metal panel to cracking,or loss ofadhesion,or both,after accelerated heat aging.Most coilcoated products are formed and bent into specific shapes toproduce a final product.These operations introduce stresses,which may be relieved by cracking of the coating after aging.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.3 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 health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D4145 Test Method for Coating Flexibility of PrepaintedSheet3.Apparatus3.1 Gravity or Forced Air Laboratory Oven,capable ofmaintaining a temperature of 60 6 3C(140 6 5F).3.2 Bench Vise,with smooth jaws or inserts,130 mm(5 in.)permanently mounted on a work table or bench,or alternativeequipment capable of making the appropriate bends.3.3 Bending Dies or Test Shims,(optional).3.4 10X magnifier,(optional).3.5 Adhesive Tape.4.Test Specimens4.1 Cut samples 75 mm(3 in.)wide(across the benddirection)by whatever length is necessary to make the appro-priate number of bends.The direction of the bend may betransverse or longitudinal to the“rolling direction”of themetalor as agreed upon between customer and vendor.5.Procedure5.1 Perform the fabrication at room temperature,25 6 1C(77 6 2F).All test specimens should be equilibrated to thesame temperature before fabricating.Different fabricationtemperatures may be used,when needed,to meet customer orvendor requirements,or both.5.2 Prepare three“T-bend”test specimens in accordancewith Test Method D4145.The T-bend used should be agreedupon between customer and vendor.5.3 Examine the T-bend for cracking and tape pick-off inaccordance with Test Method D4145 and record the results.5.4 Place the formed test specimens in the 60 6 3C(140 65F)oven for 16 h.Different times and temperatures may beused if agreed upon between the customer and vendor.5.5 Remove the test specimens and allow them to cool toroom temperature.5.6 Repeat the tape adhesion test.6.Report6.1 Report the following information:6.1.1 Reexamine the test specimens for cracking and tapepick-off.6.2 The degree of cracking and tape pick-off allowed shouldbe agreed upon between the customer and the vendor.Reportsubstrate,coating system,production or preparation date,thetape used,cracking and tape pick-off noted before heat aging,the heat aging time and temperature and cracking,and tapepick-off noted after heat aging.7.Keywords7.1 aging;coil;cracking;dry heat;fabrication;flexibility;heat aging;prepaint;pick-off;stresses;t-bend1This practice 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 June 1,2009.Published July 2009.Originally approvedin 1999.Last previous edition approved in 2003 as D6491 99(2003).DOI:10.1520/D6491-09.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard.Users of this standard are expressly advised that determination of the validity of any such patent rights,and the riskof infringement of such rights,are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of theresponsible technical committee,which you may attend.If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards,at the address shown below.This standard is copyrighted by ASTM