ASTM_B_636_-_B_636M_-_15.pdf

Designation:B636/B636M15Standard Test Method forMeasurement of Internal Stress of Plated Metallic Coatingswith the Spiral Contractometer1This standard is issued under the fixed designation B636/B636M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the use of the spiral contracto-meter for measuring the internal stress of metallic coatings asproduced from plating solutions on a helical cathode.The testmethod can be used with electrolytic and autocatalytic depos-its.1.2 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.1.3 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:E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions:3.1.1 compressive stress()stress that tends to cause adeposit to expand.3.1.2 internal stressthe net stress that remains in a depositwhen it is free from external forces.The internal stress tends tocompress or stretch the deposits.3.1.3 tensile stress(+)stress that tends to cause a depositto contract.4.Summary of Test Method4.1 The test method of measuring stress with the spiralcontractometer is based on plating on the outside of a helix.The helix is formed by winding a strip around a cylinder,followed by annealing.In operation,one end of the helix isfixed and the other is allowed to move as stresses develop.Thefree end is attached to an indicating needle through gears thatmagnify the movement of the helix.As the helix is plated,thestress in the deposit causes the helix to wind more tightly or tounwind,depending on whether the stress is compressive()ortensile(+).From the amount of needle deflection and otherdata,the internal stress is calculated.4.2 With instrument modifications,the movement of thehelix can be measured electronically instead of mechanically asdescribed in 4.1.5.Significance and Use5.1 The spiral contractometer,properly used,will givereproducible results(see 9.5)over a wide range of stressvalues.Internal stress limits with this method can be specifiedfor use by both the purchaser and the producer of plated orelectroformed parts.5.2 Plating with large tensile stresses will reduce the fatiguestrength of a product made from high-strength steel.Maximumstress limits can be specified to minimize this.Other propertiesaffected by stress include corrosion resistance,dimensionalstability,cracking,and peeling.5.3 In control of electroforming solutions,the effects ofstress are more widely recognized,and the control of stress isusually necessary to obtain a usable electroform.Internal stresslimits can be determined and specified for production control.5.4 Internal stress values obtained by the spiral contracto-meter do not necessarily reflect the internal stress values foundon a part plated in the same solution.Internal stress varies withmany factors,such as coating thickness,preparation ofsubstrate,current density,and temperature,as well as thesolution composition.Closer correlation is achieved when thetest conditions match those used to coat the part.1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved Nov.1,2015.Published December 2015.Originallyapproved in 1978.Last previous edition approved in 2010 as B636 84(2010).DOI:10.1520/B0636_B0636M-15.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.Apparatus6.1 The spiral contractometer is described by A.Brennerand S.Senderoff.2NOTE1Spiral contractometers are available from many of thesuppliers of nickel sulfamate.6.2 Helices shall be stopped-off on the inside to preventplating.Helices are available with or without a permanent inertcoating on the insides(see Appendix X1).6.3 The clamps holding the helix to the contractometer shallbe coated with an inert nonconductive coating to prevent theirplating and acting as thieves.6.4 For testing electroplating solutions,anodes are placedequidistant from the helix and symmetrically positioned toproduce even plate distribution.A minimum of four anodes isrequired.A conc