1、Designation: B 636 84 (Reapproved 2006)e1Standard Test Method forMeasurement of Internal Stress of Plated Metallic Coatingswith the Spiral Contractometer1This standard is issued under the fixed designation B 636; the number immediately following the designation indicates the year oforiginal adoption
2、 or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTENote 2 was editorially updated in May 2006.1. Scope1.1 This test method covers th
3、e 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 This standard does not purport to address all of thesafety concerns, if any,
4、 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. Terminology2.1 Definitions:2.1.1 compressive stress ()stress that tends to cause adeposit to
5、 expand.2.1.2 internal stressthe net stress that remains in a depositwhen it is free from external forces. The internal stress tends tocompress or stretch the deposits.2.1.3 tensile stress (+)stress that tends to cause a depositto contract.3. Summary of Test Method3.1 The test method of measuring st
6、ress 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 n
7、eedle 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 c
8、alculated.3.2 With instrument modifications, 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 str
9、ess limits with this method can be specifiedfor 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
10、 propertiesaffected by stress include corrosion 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
11、 be determined and specified for production 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 s
12、ub-strate, current density, and temperature, 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 f
13、rom many of the sup-pliers of nickel sulfamate.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 C
14、oatings and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved April 1, 2006. Published May 2006. Originallyapproved in 1978. Last previous edition approved in 2001 as B 636 84 (2001).2Brenner, A., and Senderoff, S., Proceedings of the American Electroplaters
15、Society, Vol 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
16、For testing 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.
17、7 L of solution. 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. Fa
18、ctors Affecting 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. Acoatin
19、g weight of 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 a
20、n opposing 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
21、helix shall 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 surfac
22、e conditions 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 impor
23、tant that thecurrent 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 i
24、ndicator and 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
25、 runs. Conversely,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 cha
26、ngesduring 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 may
27、affect the 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 Ca
28、librate the 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
29、the force required 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
30、calibrating, 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!de
31、gdef3 10268. 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 solu
32、tions appears 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 bet
33、ween the tank 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)
34、.8.4 The conditions 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 partthicknes
35、s requirements are greater than about 15 m.B 636 84 (2006)e128.4.2 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 havemu
36、ch effect on the 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 so
37、lution sample 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 adjustme
38、nts may be made 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 instr
39、ument.9. Stress 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 = densi
40、ty of deposit, 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,
41、ST, is desired: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 t
42、oinclude the following: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 va
43、riable).10.2 The 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
44、arereproducible 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 c
45、ontractometer 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 clea
46、ner at 50 6 2C.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 nicke
47、lchloride hexahydrate 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
48、 the helix by dipping in a testtube containing a stop-off lacquer solution (see Note 2). If theB 636 84 (2006)e13helix 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 w
49、iping 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 be coated because it is not immersed.NOTE X1.2Since the clamp is insulated, the cathode efficiency can becalculated and even current distribution over the helix is obtained.X1.2.13 Clean cathodically at 0.5 to 1.0 A for5sinthecleaner used in X1.2.1.X1.2.14 Rinse.X1.2.15 Immerse 50
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