ASTM_D_6677_-_07_2012.pdf

Designation:D667707(Reapproved 2012)Standard Test Method forEvaluating Adhesion by Knife1This standard is issued under the fixed designation D6677;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 test method covers the procedure for assessing theadhesion of coating films to substrate by using a knife.1.2 This test method is used to establish whether theadhesion of a coating to a substrate or to another coating(inmulti-coat systems)is at a generally adequate level.NOTE1The term“substrate”relates to the basic surface on which acoating adheres(may be steel,concrete,etc.or other coating).1.3 This method can be used in the laboratory and field.1.4 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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 health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D2197 Test Method for Adhesion of Organic Coatings byScrape AdhesionD3359 Test Methods for Measuring Adhesion by Tape TestD4541 Test Method for Pull-Off Strength of Coatings UsingPortable Adhesion TestersD7234 Test Method for Pull-Off Adhesion Strength of Coat-ings on Concrete Using Portable Pull-Off Adhesion Tes-ters3.Summary of Test Method3.1 Adhesion is determined by making an“X”cut into thecoating film to the substrate and by lifting the coating with aknife.Adhesion is evaluated qualitatively on a 0 to 10 scale.4.Significance and Use4.1 Coatings,to perform satisfactorily,must adhere to thesubstrates on which they are applied.This test method has beenfound useful as a simple means of assessing the adhesion ofcoatings.Although this method is a qualitative and a subjectivetest it has been used in industry for many years and can providevaluable information.4.2 Other adhesion test methods may be useful in obtainingquantitative results.See D2197,D3359,D4541,and D7234.4.3 The Performance Evaluation Scale(see 7.4,Table 1)isbased on both the degree of difficulty to remove the coatingfrom the substrate and the size of removed coating.4.4 This test method does not have a known correlation toother adhesion test methods(pull-off,tape,etc.).4.5 A coating that has a high degree of cohesive strengthmay appear to have worse adhesion than one that is brittle andhence fractures easily when probed.4.6 This method is not to be used on overly thick coatings,that is,those which cannot be cut to the substrate with a utilityknife in one stroke.5.Apparatus and Materials5.1 Cutting ToolSharp utility knife.5.2 Cutting GuideSteel or other hard metal straight edgeto ensure straight cuts.6.Test Specimen6.1 When this test method is used in the field,the specimenis the coated substrate on which the adhesion is to be evaluated.6.2 For laboratory use,apply the materials to be tested topanels of the composition and surface conditions on which it isdesired to determine adhesion.NOTE2If desired or specified,the coated test panels may be subjectedto a preliminary exposure such as water immersion,salt spray,or highhumidity before conducting the knife adhesion test.7.Procedure7.1 Select an area free of blemishes and surface imperfec-tions.7.2 Using a sharp knife and cutting guide,make two cutsinto the coating with a 30 to 45 angle between legs and down1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.Current edition approved Nov.1,2012.Published November 2012.Originallyapproved in 2001.Last previous edition approved in 2007 as D6677 07.DOI:10.1520/D6677-07R12.2For 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 to the substrate which intersects to form an“X.”Make each legof the angle a minimum of 38.1 mm(112in.)in length.Disregard coating removed during cutting process.7.3 Employing the point of the knife and beginning at thevertex of the angle,attempt to lift up the coating from thesubstrate or from the coating below.Rate according to Table 1.7.4 Repeat the test in two other locations on each test panel.For large structures make sufficient tests to ensure that theadhesion evaluation is representative of the whole surface.7.5 After making several cuts examine the cutting