ASTM_D_660_-_93_2019.pdf

Designation:D66093(Reapproved 2019)Standard Test Method forEvaluating Degree of Checking of Exterior Paints1This standard is issued under the fixed designation D660;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 The illustrated reference standards included in this testmethod are representative of degrees and types of checking ofexterior paint films.These standards are primarily intended forcomparative evaluation.1.2 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 checking,nthat phenomenon manifested in paintfilms by slight breaks in the film that do not penetrate throughthe last applied coating.2.1.1.1 DiscussionWhere precision is necessary in evalu-ating a paint film,checking may be described as visible(asseen with the naked eye)or as microscopic(as observed undera magnification up to ten diameters).3.Significance and Use3.1 Since checking is not easily recognizable,this testmethod is intended to provide,through definition andillustrations,a means of evaluating the degree of this filmfailure.4.Types of Checking4.1 Many types of checking are recognized,of which someare:4.1.1 Irregular Pattern TypeChecking in which the breaksdevelop in the surface of the film in no definite pattern.4.1.2 Line and Short Parallel TypeChecking in which thebreaks in the surface of the film are generally arranged inparallel lines.4.1.3 Switch TypeChecking in which the breaks in thesurface of the film form short and long irregular lines crossingeach other in a wire brushed pattern.4.1.4 Crow Foot TypeChecking in which the breaks in thesurface of the film form in a definite three-pronged pattern withthe breaks running from a center and forming an angle of about120 between the prongs.4.1.5 Mosaic TypeChecking in which the breaks in thesurface of the film form straight sided,geometric patternswhich join on all sides.4.1.6 Shrinkage TypeChecking in which the breaks in thesurface of the film usually form individual short breaks withshorter irregular breaks progressing at right angles.4.1.7 Short,Random TypeChecking in which breaks in thesurface of the film form short,irregular patterns.These breaksare usually individual and do not join.4.1.8 Sigmoid TypeChecking in which the breaks in thesurface of the film form oval patterns.These oval shapes rarelycomplete their circle.5.Use of Illustrated Reference Standards25.1 The use of the reference standards shown in Fig.1requires the following precautions:5.1.1 Since the type and degree of failure may vary over anygiven area,a representative portion should be rated.It isrecommended that ratings be made at several locations,notingtypes and degree of failure.5.1.2 Care must be taken to recognize that several types ofchecking may be present on the same surface.5.1.3 Paint films may collect excessive quantities of dirt,which may mask the type and degree of failure.If necessary,dirt should be removed by careful and gentle brushing with amoderately soft brush.Care must be taken not to damage thefinish.5.1.4 Fig.2 illustrates microscopic checking under 10-diameter magnification.5.1.5 For convenience in recording the data obtained,therecords should be kept on forms agreed upon between thepurchaser and the seller.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.25 on Evaluation of Weathering Effects.Current edition approved Oct.1,2019.Published October 2019.Originallyapproved in 1944.Last previous edition approved in 2011 as D660 93(2011).DOI:10.1520/D0660-93R19.2TNO illustrated reference standards are provided as a courtesy of TNO(Toegepast Natuurwetenschappelk Onderzock),Schoemakerstraat 97,Delft,Neth-erland.Copyright ASTM International,100 Barr Harbor Drive,PO 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 by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 6.Precision and Bias6.1 No precision or bias statement has been established forthis test method.7.Keywords7.1 checking;evaluations;reference standardsFIG.1 Illustrated Reference StandardD660