ASTM_B_555_-_86_2013.pdf

Designation:B55586(Reapproved 2013)Standard Guide forMeasurement of Electrodeposited Metallic CoatingThicknesses by Dropping Test1This standard is issued under the fixed designation B555;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 guide covers the use of the dropping test tomeasure the thickness of electrodeposited zinc,cadmium,copper,and tin coatings.NOTE1Under most circumstances this method of measuring coatingthicknesses is not as reliable or as convenient to use as an appropriatecoating thickness gauge(see Test Methods B499,B504,and B568).1.2 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:2B487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination ofCross SectionB499 Test Method for Measurement of Coating Thicknessesby the Magnetic Method:Nonmagnetic Coatings onMagnetic Basis MetalsB504 Test Method for Measurement of Thickness of Metal-lic Coatings by the Coulometric MethodB568 Test Method for Measurement of Coating Thicknessby X-Ray SpectrometryD1193 Specification for Reagent Water3.Summary of Guide3.1 A dropping test3consists of applying dropwise a corro-sive solution,at a constant rate,to the electroplated surface,and measuring the time required to penetrate the coating andexpose the substrate;this time is proportional to the coatingthickness.4.Significance and Use4.1 The thickness of a metal coating is often critical to itsperformance.4.2 This procedure is useful for an approximate determina-tion when the best possible accuracy is not required.For morereliable determinations,the following methods are available:Test Methods B487,B499,B504,and B568.4.3 This test assumes that the rate of dissolution of thecoating by the corrosive reagent under the specified conditionsis always the same.5.Factors Affecting the Accuracy5.1 The following factors will affect the accuracy of acoating thickness measurement made by this method:5.1.1 Cleanliness of SurfaceAny foreign material on thesurface to be tested,including lacquer,grease,corrosionproducts,and conversion coatings,will interfere with the testand must be removed.Tarnish and conversion coatings canoften be removed by mild burnishing with a soft,clean pencileraser.5.1.2 Concentration of Test SolutionVariation from thestated concentrations will introduce an error unless the thick-ness factor is adjusted accordingly.Test solutions cannot bereused.5.1.3 TemperatureThe thickness factor for a givensolution,being a function of the temperature,must be knownfor the temperature at which the test is made.Specimens to betested should be allowed to reach room temperature beforetesting.5.1.4 Dropping RateThe thickness factor is also a func-tion of the dropping rate.The thickness factors given in Section10 are for a dropping rate of 100 drops/min and will remainvalid for the range of 95 to 105 drops/min.5.1.5 Solution DrainageThe thickness factors given inSection 10 are valid only if the test solution is rapidly drainedoff,as from a flat surface inclined 45 from the horizontal.Thetest cannot be made on a horizontal surface or at a location thatdoes not permit rapid drainage.1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.10 on TestMethods.Current edition approved Dec.1,2013.Published December 2013.Originallyapproved in 1971.Last previous edition approved in 2007 as B555 86(2007).DOI:10.1520/B0555-86R13.2For 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.3Such tests were described by Hull,R.O.,and Strausser,P.,Monthly Review,American Electroplaters Society,MRAEA,Vol 22,1935,p.9,and by Brenner,A.,Proceedings,American Electroplaters Society,AEPPB,Vol 27,1939,p.204.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.1.6 Drop SizeVariation in drop size may alter thepenetration rate.The tip of the dropping apparatus shouldconform to the dimensions given in Fig.1 and should be keptclean.5.1.7 Alloy LayerThe presence of an alloy layer at thecoating-substrate interface may obscure the end point andintroduce an uncertainty as to the amount of alloy included inthe thickness measurement.5.1.8 Detection of End PointThe end point(the time atwhich the coating has been penetrated and the s