1、Designation: B 490 92 (Reapproved 2008)e1Standard Practice forMicrometer Bend Test for Ductility of Electrodeposits1This standard is issued under the fixed designation B 490; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 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.e1NOTEThe units statement in subsection 1.5 was corrected editorially in April 2008.1. Scope1.1 This practice describes a pro
3、cedure for measuring theductility of electrodeposited foils.21.2 This practice is suitable only for the evaluation ofelectrodeposits having low ductility.1.3 The obtained ductility values must only be consideredsemi-quantitative because this test has a significant operatordependence.1.4 This practic
4、e is best used for in-house process controlwhere measurements are always made by the same operator. Achange in ductility value can be used as an indication ofpossible changes in the electroplating solution.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement
5、 are included in thisstandard.1.6 This standard does not purport to address the safetyproblems, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to
6、use.2. Referenced Documents2.1 ASTM Standards:3B 177 Guide for Engineering Chromium Electroplating3. Summary of Practice3.1 This practice consists of measuring the bend of a foilheld between the jaws of a micrometer; these are closed untilfracture or cracks appear.4. Significance and Use4.1 This pra
7、ctice is useful as one method of controllingsome electroplating solutions. It serves to indicate the presenceof contamination or some other adverse condition.4.2 Ductility measurements are of particular value whenelectroplated parts are to be subjected to moderate stress suchas that involved in bolt
8、ing an electroplated bumper to anautomobile.NOTE 1The foils used in this practice are typically 25 to 40 m thick.Foils in this thickness range do not have the same properties as bulk metal.For example, a nickel electrodeposit 0.5 mm thick, prepared in purifiedbright nickel electroplating solutions f
9、or which this test is being used, hadless than 3 % elongation in a tension test, and could not be bent to a 90angle without complete fracture. However, foils 25 to 40 m thick,electroplated at the same time, had micrometer ductility values in the 10to 25 % range.5. Apparatus5.1 Micrometer, 25-mm with
10、 flat jaws to measure thethickness and to compress the foil.5.2 Hand or Power Shear, grinding wheel, or hack saw, totrim the edges of the electroplated panel and to separate the foilfrom the basis metal.5.3 Pair of Sharp Scissors to cut the test specimens.6. Test Specimens6.1 An electrodeposit shall
11、 be prepared using a basis metalwith a smooth surface from which the electrodeposit can bereadily separated. A stainless steel or nickel electroplated steelpanel may be used for this purpose, prepared as in 6.2.6.2 Apiece of cold-rolled steel, of any convenient size, suchas 100 by 150 mm, shall be p
12、roperly cleaned, acid dipped, andelectroplated with approximately 7.5 m of nickel. Afterrinsing, the specimen shall be cleaned anodically for 15 s in ahot alkaline cleaner, rinsed, acid dipped in about 1 Nsulfuricacid (about 27 mL of concentrated sulfuric acid added to about900 mL of cold water, mix
13、ed, and diluted with cold water to 1L), and immediately placed in the electroplating solution of themetal to be tested. An electrodeposit 25 to 40 m thick shall beelectroplated on the prepared surface. The deposit shall beplated at an average current density and under conditions1This practice is und
14、er the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved April 1, 2008. Published April 2008. Originallyapproved in 1968. Last previous edition approved in 2003 as B 490 92 (2003).2For
15、a discussion of this test see Mohrnheim, A. F., “The Bend Test forMeasuring the Strain Limit of Surfaces,” Plating, Vol 50, 1963, pp. 10941099.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vo
16、lume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(agitation, temperature, etc.) approximating those used on partsplated in the solution being tested.6.3
17、 The volume of the plating solution used to produce thetest specimen shall be sufficient so that the concentration of theadditives do not drop below 90 % of original additive concen-tration. Additions to the test solution shall not be made sincethey can alter the original composition.NOTE 2The ducti
18、lity of nickel, with or without chromium, will varydepending upon plating conditions, contamination, and the additivesystem used. If electroplated with chromium, the foil may require heatingor aging to overcome temporary hydrogen embrittlement. A procedure toovercome hydrogen embrittlement is covere
19、d in 8.2 of Guide B 177.6.4 Proper preparation of the surface from which the foilmust be separated undamaged is critical. Buffed nickel orbuffed stainless steel, which may require anodic treatment, in ahot alkaline cleaner as defined in 6.2, can be used as the basismetal. Steel or nickel dipped in a
20、 chromating solution, such asused for chromating zinc, can be used as the basis metal.Copper or brass, masked on one side, can be used as the basismetal, and can be subsequently dissolved from the coating tobe tested. Because the dissolving step can embrittle the testdeposit, the test deposit must b
21、e aged as stipulated in Note 2.6.5 Cut off the edges of the panel with a power or handshear, or by any convenient method that permits ready sepa-ration of the foil from the basis metal.6.6 Using a pair of sharp scissors, cut two or more testspecimens, about 5 to 75 mm from the center of the foil.7.
22、Procedure7.1 Measure the thickness of the test foil with the microme-ter at the point of bending. Bend the test foil in the shape of a“U” with the side of the foil that was against the basis metalfacing inward in the “U.” Place the bent foil between the jawsof the micrometer so that as the jaws are
23、closed, the bendremains between the jaws. Close the micrometer jaws slowlyuntil the foil cracks (Note 3). Use an average of two or morefoil tests. Record the micrometer reading as 2R and thethickness of the foil as determined by the micrometer as T.7.2 At times, no single crack may develop over the
24、convexsurface. If jagged cracks or a series of shorter cracks develop(excluding edges), they signify failure. If no cracks develop,the maximum ductility values are obtained.8. Calculation8.1 Two standard formulas are used to compute ductility:Ductility, percent 5 100T/2R2T! (1)Maximum value is 100 %
25、. (1)Ductility, ratio 5 T/2R (2)Maximum value is 0.5. (2)8.1.1 Either formula can be used but they give differentvalues for the same ductility. It is important that the formula beconsistently used for purpose of comparison. When reportingductility values, the formula must be indicated.8.2 It should
26、be understood that this value bears no simplerelation to the percentage elongation obtained through tensionor other tests. The ductility of this type of low-ductilityelectrodeposit varies with the thickness. Usually the greater thethickness, the lower is the percentage ductility for these foils.(Not
27、e 2).NOTE 3With foils of a ductility of 70 % or greater using formula100T/(2RT) or 0.4, using formula T/2R (see 8.1). It is helpful toexamine the foil at low magnification (103) while it is still in themicrometer.ASTM International takes no position respecting the validity of any patent rights asser
28、ted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by
29、the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receiv
30、e careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Intern
31、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).B 490 92 (2008)e12
