ASTM_B_651_-_83_2015.pdf

Designation:B65183(Reapproved 2015)Standard Test Method forMeasurement of Corrosion Sites in Nickel Plus Chromiumor Copper Plus Nickel Plus Chromium ElectroplatedSurfaces with Double-Beam Interference Microscope1This standard is issued under the fixed designation B651;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 provides a means for measuring theaverage dimensions and number of corrosion sites in anelectroplated decorative nickel plus chromium or copper plusnickel plus chromium coating on steel after the coating hasbeen subjected to corrosion tests.This test method is useful forcomparing the relative corrosion resistances of different elec-troplating systems and for comparing the relative corrosivitiesof different corrosive environments.The numbers and sizes ofcorrosion sites are related to deterioration of appearance.Penetration of the electroplated coatings leads to appearance ofbasis metal corrosion products.1.2 The values stated in SI units are to be regarded as thestandard.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:2B487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination ofCross Section3.Summary of Test Method3.1 The depths and diameter of corrosion pits or the widthsof corrosion crevices,and the number of pits per squaremillimetre or crevices per linear millimetre on a specimensurface,are determined using optical aids(magnifier,microscope,and interference microscope).The values arecompared to dimensions and numbers of corrosion sitesobtained from other specimens.4.Significance and Use4.1 Different electroplating systems can be corroded underthe same conditions for the same length of time.Differences inthe average values of the radius or half-width or of penetrationinto an underlying metal layer are significant measures of therelative corrosion resistance of the systems.Thus,if the pitradii are substantially higher on samples with a given electro-plating system,when compared to other systems,a tendencyfor earlier failure of the former by formation of visible pits isindicated.If penetration into the semi-bright nickel layer issubstantially higher,a tendency for earlier failure by corrosionof basis metal is evident.5.Apparatus5.1 Double-Beam Interference Microscope(lateral magnifi-cation about 100),capable of producing,with white light,avisible group of interference fringes,and equipped with acalibrated fine focus and a graduated bifilar(movable crosshair)eyepiece.5.2 Magnifier or Microscope(10 to 20),with lightsource.5.3 Rule,graduated in millimetres,and a scriber for pro-ducing visible lines on the specimen surface.5.4 Microscope,with a magnification capability of 500,equipped with a bifilar eyepiece,for making measurements onopaque surfaces.5.5 Equipment for mounting and polishing of specimens formicroscopical cross-sectional measurements.6.Specimen Preparation6.1 Clean the corroded specimen surface with an agent oragents that remove soil and corrosion products,but do notsignificantly change the surface of the corrosion sites.Scouringpowder may be used to remove insoluble corrosion products,organic solvent to remove road tar,water accompanied bygentle abrasion with a cloth to remove lightly adherent soil,etc.1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.05 onDecorative Coatings.Current edition approved March 1,2015.Published April 2015.Originallyapproved in 1978.Last previous edition approved in 2010 as B651 83(2010).DOI:10.1520/B0651-83R15.2For 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 6.2 Mask with paint or tape that portion of the specimensurface on which no measurements of pits or cracks will bemade.Alternatively,a gasketed cell pressed onto the surfacemay be used.The opening in the gasket will define the area tobe stripped.NOTE1If pitted,the area selected for measurement should contain atleast 100 pits or be as large as 50 by 50 mm.If the area contains cracks,the location for measurement should contain at least 100 cracks,or be atleast 50 mm long.6.3 Strip the chromium anodically at 6 to 8 V in a solutioncontaining