1、Designation: B 490 92 (Reapproved 2003)Standard 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 o
2、f 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.1. Scope1.1 This practice describes a procedure for measuring theductility of electrodeposited foils.21.2 This practice is suit
3、able 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 practice is best used for in-house process controlwhere measurements are always made by the s
4、ame operator. Achange in ductility value can be used as an indication ofpossible changes in the electroplating solution.1.5 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 saf
5、ety andhealth practices and determine the applicability of regulatorylimitations prior to 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 micro
6、meter; these are closed untilfracture or cracks appear.4. Significance and Use4.1 This practice 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 w
7、henelectroplated parts are to be subjected to moderate stress suchas that involved in bolting 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
8、 electrodeposit 0.5 mm thick, prepared in purifiedbright nickel electroplating solutions for 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
9、 micrometer ductility values in the 10to 25 % range.5. Apparatus5.1 Micrometer, 25-mm with 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 Pai
10、r of Sharp Scissors to cut the test specimens.6. Test Specimens6.1 An electrodeposit shall 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
11、.6.2 Apiece of cold-rolled steel, of any convenient size, suchas 100 by 150 mm, shall be properly 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 N sulf
12、uricacid (about 27 mL of concentrated sulfuric acid added to about900 mL of cold water, mixed, 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 dep
13、osit shall beplated at an average current density and under conditions(agitation, temperature, etc.) approximating those used on partsplated in the solution being tested.1This practice is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility
14、of Subcommittee B08.10 onTest Methods.Current edition approved Oct. 1, 2003. Published October 2003. Originallyapproved in 1968. Last previous edition approved in 1998 as B 490 92 (1998).2For a discussion of this test see Mohrnheim, A. F., “The Bend Test forMeasuring the Strain Limit of Surfaces,” P
15、lating, 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 volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM Internatio
16、nal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 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
17、test solution shall not be made sincethey can alter the original composition.NOTE 2The ductility 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 overco
18、me temporary hydrogen embrittlement. A procedure toovercome hydrogen embrittlement is covered 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 al
19、kaline cleaner as defined in 6.2, can be used as the basismetal. Steel or nickel dipped in a 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 tob
20、e tested. Because the dissolving step can embrittle the testdeposit, the test deposit must be 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 sha
21、rp scissors, cut two or more testspecimens, about 5 to 75 mm from the center of the foil.7. 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 inwar
22、d in the “U”. Place the bent foil between the jawsof the micrometer so that as the jaws are 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 f
23、oil as determined by the micrometer as T.7.2 At times, no single crack may develop over the 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 form
24、ulas are used to compute ductility:Ductility, percent 5 100T/2R2T! (1)Maximum value is 100 %. (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
25、 of comparison. When reportingductility values, the formula must be indicated.8.2 It should 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.
26、Usually the greater thethickness, the lower is the percentage ductility for these foils.(Note 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 themicrom
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30、mmittee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 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 (2003)2
