ASTM_D_6900_-_10_2015.pdf

Designation:D690010(Reapproved 2015)Standard Test Method forWet Adhesion of Latex Paints to a Gloss Alkyd EnamelSubstrate1This standard is issued under the fixed designation D6900;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 method covers a procedure for measuring byscrubbing the adhesion of latex paints to glossy alkyd enamelsubstrates after exposure to wet conditions.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:2D523 Test Method for Specular GlossD714 Test Method for Evaluating Degree of Blistering ofPaintsD2486 Test Methods for Scrub Resistance of Wall PaintsD3924 Specification for Environment for Conditioning andTesting Paint,Varnish,Lacquer,and Related MaterialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE177 Practice for Use of the Terms Precision and Bias inASTM Test Methods3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 wet adhesion,nthe ability of a coating to resistremoval by scrubbing from the surface beneath it after expo-sure to wet conditions and abrasion.4.Summary of Test Method4.1 Test paints,with optional control paint,are drawn downusing a 7-mil clearance Dow applicator(11 m2/L)across acured alkyd gloss enamel previously drawn down on a black orwhite plastic panel.4.2 The drawdown films are allowed to dry under standard-ized conditions.Then,eighteen cuts are made to form a 6 by 10cut block,creating sixty 6.4 mm(0.25 in)squares,in the centerof each film with a razor blade.4.3 The panels are then soaked for 30 min in ambient tapwater.The panel is mounted in a washability tester and 20 mLof water are applied.The panel is then scrubbed for up to 500cycles or until all of the squares within each block arecompletely removed.5.Significance and Use5.1 After application to either interior or exterior surfaces,latex paints may be subjected to conditions of high humidity,condensation,or precipitation.This may sometimes lead to aloss of adhesion to the substrate over which they have beenapplied.This method is a quantitative measure of the adhesionof latex paints to glossy substrates under such conditions.6.Apparatus6.1 Constant temperature/humidity room in accordance withSpecification D3924 23 6 2C(73.5 6 3.5F)and 50 6 5%relative humidity.6.2 Drawdown Plate.6.3 Straight Line Washability Tester and Accessories,perTest Methods D2486.6.4 Nylon Bristle Brush and Accessories(nominal weight455 g),having nylon brush bristles in 5/4 pattern extending 19mm(34in.)from block(as per Test Methods D2486).6.5 Dow Film Applicator,having 7-mil(0.18-mm)clearanceby 5.2-in.(132-mm)width.applicator blade.6.6 Single-edge Razor Blade,in safety holder.6.7 Metal Straight Edge,(or appropriate guide).1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.42 on Architectural Coatings.Current edition approved June 1,2015.Published June 2015.Originallyapproved in 2003.Last previous edition approved in 2010 as D6900 10.DOI:10.1520/D6900-10R15.2For 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 7.Reagents and Materials7.1 A ready-mix deep-tint alkyd gloss enamel with a 60gloss of at least 65 as measured in accordance with TestMethod D523(or alkyd as agreed upon by the purchaser andsupplier).7.2 Plastic test panels as used in Test Methods D2486.38.Procedure8.1 Preparation of the Alkyd Substrate PanelsAttach theplastic panel to the drawdown plate and drawdown the alkydgloss enamel lengthwise using a 7-mil clearance Dow appli-cator.The time for application should be fairly slow3 to 4 sfrom end to end.The drawdown must be free of ridges,holidays,specks,or other imperfections,which may affectadhesion.8.1.1 Allow the alkyd gloss enamel to air-dry in a horizontalposition.Allow to cure typically for a minimum of three weeks.Panels are to be used between three to six weeks from the dateof preparation.Wet adhesion with some latex paints may bedramatically reduced if the alkyd is allowed to cure for morethan six we