ASTM_D_7835_-_D_7835M_-_13.pdf

Designation:D7835/D7835M13Standard Test Method forDetermining the Solvent Resistance of an Organic Coatingusing a Mechanical Rubbing Machine1This standard is issued under the fixed designation D7835/D7835M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers a mechanical rub method forassessing the solvent resistance of an organic coating thatchemically and/or physically changes during the curing pro-cess.This technique can be used in the laboratory,in the field,or in the fabricating shop.1.2 This test method does not specify the solvent,number ofdouble rubs,or expected test results.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 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:2D740 Specification for Methyl Ethyl KetoneD4138 Practices for Measurement of Dry Film Thickness ofProtective Coating Systems by Destructive,Cross-Sectioning MeansD5402 Practice for Assessing the Solvent Resistance ofOrganic Coatings Using Solvent RubsD5796 Test Method for Measurement of Dry Film Thicknessof Thin-Film Coil-Coated Systems by Destructive MeansUsing a Boring DeviceD6132 Test Method for Nondestructive Measurement of DryFilm Thickness of Applied Organic Coatings Using anUltrasonic Coating Thickness GageD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic,Nonconductive Coat-ings Applied to Non-Ferrous Metals3.Terminology3.1 Definitions:3.1.1 double rub,none complete forward and backwardmotion over a coated surface under specific conditions,whichare characterized by the force applied normal to the surface,thelength of travel,and rate of speed.4.Summary of Test Method4.1 An automated machine is used to test the solventresistance of a coating by rubbing a cloth saturated with thesolvent across the coating and counting the number of strokes(double rubs)to coating break-through or failure.5.Significance and Use5.1 Many coatings used in the coil coating and otherindustries achieve a degree of solvent resistance after they haveexperienced a bake condition characterized by exposure toelevated temperatures in an oven over time.Insufficient bake,or occasionally over bake,may affect the intended chemicalbonds or physical curing of the film and result in reducedsolvent resistance.5.2 The mechanical rubbing machine provides consistentstroke length,rate,pressure,and contact area that are notsubject to variables such as human fatigue(see PracticeD5402).5.3 Factors other than bake can influence degree of solventresistance of a coated surface.Paint film chemistry andcomposition,surface preparation,oven dwell time,oven airvelocity,ambient oven temperature,oven profiling,filmthickness,etc.,all are influential.The test solvent used in therub machine has a significant effect on the number of doublerubs measured.Common solvents used for these tests includeMethyl Ethyl Ketone(MEK),Methyl Isobutyl Ketone(MIBK),and IsopropylAlcohol to name a few.The specific solvent to beused and the umber of double rubs to be achieved should be1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.53 on Coil Coated Metal.Current edition approved July 1,2013.Published August 2013.DOI:10.1520/D7835/D7835M-132For 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 agreed upon between manufacturer and user for any givencoating system,thickness,and application.6.Apparatus6.1 Solvent Rub Machinewith operator instructions.6.1.1 The machine may be any suitable device that drives amechanical finger through double rubs across the same path ona coated surface and has the following characteristics(see Fig.1).6.1.1.1 The mechanical finger must have a flat,smooth,circular surface 1.6 6 0.2 cm 0.625 6 0.08 in.diameter.6.1.1.2 A weighted block must apply 3000 6 50 g ofpressure to the mechanical finger.6.1.1.3