1、Designation: B636 84 (Reapproved 2010)Standard Test Method forMeasurement of Internal Stress of Plated Metallic Coatingswith the Spiral Contractometer1This standard is issued under the fixed designation B636; the number immediately following the designation indicates the year oforiginal adoption or,
2、 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 covers the use of the spiral contracto-meter for measuring the
3、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
4、 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 therespon
5、sibility 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. Terminology2.1 Definitions:2.1.1 compressive stress ()stress that tends to cause adeposit to expand.2.1.2 internal stressthe net stre
6、ss that remains in a depositwhen it is free from external forces. The internal stress tends tocompress or stretch the deposits.2.1.3 tensile stress (+)stress that tends to cause a depositto contract.3. Summary of Test Method3.1 The test method of measuring stress with the spiralcontractometer is bas
7、ed 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 movem
8、ent 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.3.2 With instrument modificatio
9、ns, the movement of thehelix can be measured electronically instead of mechanically asdescribed in 3.1.4. Significance and Use4.1 The spiral contractometer, properly used, will givereproducible results (see 8.5) over a wide range of stressvalues. Internal stress limits with this method can be specif
10、iedfor use by both the purchaser and the producer of plated orelectroformed parts.4.2 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 cor
11、rosion resistance, dimensionalstability, cracking, and peeling.4.3 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 producti
12、on control.4.4 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 of sub-strate, current density, and temperatu
13、re, as well as the solutioncomposition. Closer correlation is achieved when the testconditions match those used to coat the part.5. Apparatus5.1 The spiral contractometer is described by A. Brennerand S. Senderoff.2NOTE 1Spiral contractometers are available from many of the sup-pliers of nickel sulf
14、amate.5.2 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).1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility
15、of Subcommittee B08.10 onTest Methods.Current edition approved Nov. 1, 2010. Published November 2010. Originallyapproved in 1978. Last previous edition approved in 2006 as B636 84(2006)e01.DOI: 10.1520/B0636-84R10.2Brenner, A., and Senderoff, S., Proceedings of the American ElectroplatersSociety, Vo
16、l 35, 1948, p. 53.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 The clamps holding the helix to the contractometer shallbe coated with an inert nonconductive coating to prevent theirplating and acting as thieves.5.4 For testing
17、 electroplating solutions, anodes are placedequidistant from the helix and symmetrically positioned toproduce even plate distribution. A minimum of four anodes isrequired. A concentric anode arrangement is preferred.5.5 Laboratory tests on electroplating solutions shall utilizeat least 3.7 L of solu
18、tion. A 4-L beaker with an annular anodearrangement is convenient. Use of this volume or larger willminimize solution changes due to electrolysis during the test.5.6 Laboratory tests on autocatalytic plating solutions aredone in a 1-L, tall-form beaker. Obviously, no anodes are used.6. Factors Affec
19、ting Accuracy6.1 Variations in the preparation of the helix may causesubstantial variations in results.6.1.1 Stop-off material shall be applied properly to theinterior of the helix. The stop-off material shall be thin andflexible to permit the helix to move freely during the test. Acoating weight of
20、 less than 50 mg/dm2is satisfactory.NOTE 2The inside must be stopped-off with some inert, flexiblecoating. One acceptable stop-off material is “Microstop.” One part of“Microstop” is diluted with two parts of acetone before use. Any nickeldeposited on the inside of the helix will exhibit an opposing
21、effect.6.1.2 Helices that have been permanently coated on theinside with TFE-fluorocarbon may give variable results whentesting near-zero stresses.6.1.3 Cleaning variations and surface preparation of thehelix before the test can produce varying results. For example,electrocleaning of the helix shall
22、 always be cathodic andcontrolled with respect to current, time, and temperature.Anodic cleaning at this stage can give wide variations. Abra-sive cleaning of the helix and the use of etchants shall beavoided.6.1.4 Very thin deposits of less than about 3 m areinfluenced more by the surface condition
23、s and preparation ofthe helix than are thicker deposits.6.2 Internal stress varies with current density used in elec-troplating. The variation is not predictable and depends on themetal being deposited, impurities or additives, and the currentdensity range under consideration. It is important that t
24、hecurrent be measured and controlled closely throughout thestress test. Variations in currents shall be held to less than 2 %.6.3 Because the temperature of the plating solution mayaffect the internal stress, it shall be maintained within 2Cduring the test. The initial rest point of the indicator an
25、d thefinal rest point are both taken at the operating temperature ofthe plating solution to eliminate thermal stresses.6.4 The solution composition shall not vary during the test.Usually, if the repeatability tests in 8.5 are met, the solution canbe assumed to be unchanged during the test runs. Conv
26、ersely,when the repeatability tests are not met, the plating solutionshall be analyzed to determine if any changes in solutioncomposition have occurred during the test.6.4.1 Tests run on electroplating solutions using insoluble orinefficient anodes could result in significant solution changesduring
27、the test.6.4.2 When testing autocatalytic plating solutions, the con-stituents of the plating solution may be significantly depletedduring the test, unless replenished.6.5 A relationship between the surface area to be plated andthe volume of autocatalytic plating solutions exists that mayaffect the
28、character of the deposit. In testing autocatalyticplating solutions, the ratio of plated surface area to the volumeof solution that is normally used in the plating tank shall bemaintained. When using proprietary solutions, the suppliersrecommendation shall be followed.7. Calibration7.1 Calibrate the
29、 instrument as directed in the manufactur-ers instructions.7.2 The frequency of calibration will vary with use andextent of attack on the helices from the chemical stripping.When visible attack is noted, discard the helix.7.3 The calibration procedure consists essentially of deter-mining the force r
30、equired per degree of dial deflection. Aknown mass is suspended over a small pulley on a lever armwith the helix mounted in place. The degree of deflection isread from the dial. The data required for the calibrationcalculations as expressed in metric units are as follows:w = mass used in calibrating
31、, kg,a = length of lever arm, m,p = pitch of helix, m,t = thickness of the strip used to make the helix, m,degdef= degree deflection; difference in dial readingscaused by mass,g = 9.8 m/s2(acceleration of free fall), andZ =calibration constant of the helixSMPam degdefDwhereZ 52w!a!g!pt!degdef3 10268
32、. Procedure8.1 The procedure will vary with the solution being tested.Follow the instructions given by the supplier carefully. Varia-tions in the procedure can produce variations in results. Giveappropriate attention to the factors in Section 6. A detailedprocedure for nickel plating solutions appea
33、rs inAppendix X1.8.2 Position the spiral contractometer in electroplating so-lutions so that it is equidistant from the anodes. Position theanodes on at least four sides when they are used in a productiontank or use a concentric anode arrangement. Do not place thespiral contractometer between the ta
34、nk anodes and the workbeing plated in a production tank. A separate ammeter andcurrent control are required. If the test is run on a sample of thesolution, use a 4-L beaker.8.3 When testing autocatalytic plating solutions, maintainthe proper surface area-to-solution volume ratio (see 6.5).8.4 The co
35、nditions of the test are usually chosen to matchthose of the production parts as closely as practicable.8.4.1 The thickness of the deposit plated on the helix maynot be required to be the same as the thickness plated onproduction parts. This is especially true when production partthickness requireme
36、nts are greater than about 15 m.B636 84 (2010)28.4.2 The current density used for the spiral contractometeris sometimes lower than that of production parts. Electroplat-ing at the lower current density will often indicate thecumulative effects of solution impurities before these havemuch effect on t
37、he work being plated at the higher currents.This information can be used as a measure of the solutionpurity and will allow planning for corrective or purificationprocedures.8.5 Repeatability:8.5.1 Consider the procedure repeatable if the results ofthree consecutive tests on the same solution sample
38、produceinternal stress values that do not vary more than 610 % fromthe mean of the three values.8.5.2 For near zero stress values, 10 to +10 MPa, it is moredifficult to detect small changes with the contractometer and anacceptable range for repeatability is 65 MPa.8.6 Solution adjustments may be mad
39、e during the test,especially when testing autocatalytic solutions and electroplat-ing solutions using insoluble anodes.8.7 Clean the instrument after each use and before storage.This is to prevent solution that may creep up the shaft fromcrystallizing and binding or corroding the instrument.9. Stres
40、s Calculations9.1 Data Required:Z = calibration constant for the helix, MPa/(m degdef),D = change in dial reading during the test, deg, andt = thickness of the deposit on the helix, m.t can be calculated from the additional data:A = plated area, m2,W = mass of deposit, kg, andd = density of deposit,
41、 kg/m3.Then t = W/(d)AInternal stress, S,inMPa5Z 3 Dt(1)NOTE 3This value is an average stress and is uncorrected for theeffects of the differences in Youngs modulus between the helix and thedeposit. It also assumes a relatively thin deposit on the helix. If a correctedor truer stress, ST, is desired
42、:ST5 SF1 1SE03 tE 3tDG(2)where:E0= Youngs modulus of the deposit, andE = Youngs modulus of the helix.Normally, the correction made above is less than theexperimental errors in the procedure and is infrequently used.10. Report10.1 When reporting internal stress values, it is necessary toinclude the f
43、ollowing:10.1.1 Metal deposited and the plating solution composi-tion,10.1.2 Instrument used (spiral contractometer),10.1.3 Thickness of deposit on helix,10.1.4 Current density (omit if autocatalytic deposits arebeing tested),10.1.5 Temperature, and10.1.6 pH (if it is a controllable variable).10.2 T
44、he unit for expressing internal stress is the megapas-cal (MPa). One megapascal is one meganewton per squaremetre (MN/m2), approximately 145 psi.11. Precision and Bias11.1 Results are reproducible to about 610 % except for thenear-zero range of 610 MPa. In the near-zero range, results arereproducibl
45、e to about 65 MPa.12. Keywords12.1 internal stress test; metallic depositAPPENDIX(Nonmandatory Information)X1. PROCEDURE FOR STRESS DETERMINATION OF NICKEL ELECTRODEPOSITSX1.1 ScopeX1.1.1 The following is a detailed procedure for the deter-mination of internal stress using the spiral contractometer
46、onnickel electroplating solutions. Some modifications can bemade to adapt this procedure for use with other metal platingsolutions.X1.2 Preparation of Helix (use a stainless steel helix)X1.2.1 Clean helix (as cathode) by electrocleaning at 4.0 to5.0 A for 15 s in an alkaline steel cleaner at 50 6 2C
47、.X1.2.2 Rinse.X1.2.3 Immerse in 50 %, v/v, hydrochloric acid for 3 to 5 s.X1.2.4 Rinse.X1.2.5 Nickel strike at 5.0Afor 1 min in a standard Woodsnickel solution. The nickel strike is optional. If omitted,proceed to X1.2.9.NOTE X1.1The nickel strike solution contains 240 g/litre of nickelchloride hexa
48、hydrate and 12.5 % v/v of concentrated hydrochloric acid. Itis operated at room temperature using nickel anodes.X1.2.6 Rinse.X1.2.7 Immerse in 50 %, v/v hydrochloric acid for 3 to 5 s.X1.2.8 Rinse.X1.2.9 Dry the helix with acetone and weigh to nearest 1mg.X1.2.10 Stop-off the inside of the helix by
49、dipping in a testtube containing a stop-off lacquer solution (see Note 2). If theB636 84 (2010)3helix has a permanently bonded, inert coating, omit this step,the step described in X1.2.11, and the stripping of the stop-off.X1.2.11 Remove the lacquer from the outside of the helixby wiping with acetone and then trichloroethylene. Do nottouch the cleaned helix with bare fingers.X1.2.12 Mount the helix with clamps. Stop-off the outsideof the bottom clamp or use a bottom clamp, bolt, and nut madeof resistant plastic such as TFE-fluorocarbon. The top clampneed not
