1、Designation: B555 86 (Reapproved 2012)Standard Guide forMeasurement of Electrodeposited Metallic CoatingThicknesses by Dropping Test1This standard is issued under the fixed designation B555; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, 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 guide covers the use of the dropping test tomeasure the thickness of electrodeposited zinc, c
3、admium,copper, and tin coatings.NOTE 1Under most circumstances this method of measuring coatingthicknesses is not as reliable or as convenient to use as an appropriatecoating thickness gauge (see Test Methods B499, B504, and B568).1.2 The values stated in SI units are to be regarded asstandard. No o
4、ther units of measurement are included in thisstandard.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
5、 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination ofCross SectionB499 Test Method for Measurement of Coating Thicknessesby the Magnetic Method: Nonmagnetic Coatings onMa
6、gnetic Basis MetalsB504 Test Method for Measurement of Thickness of Metal-lic Coatings by the Coulometric MethodB568 Test Method for Measurement of Coating Thicknessby X-Ray SpectrometryD1193 Specification for Reagent Water3. Summary of Guide3.1 A dropping test3consists of applying dropwise a corro-
7、sive solution, at a constant rate, to the electroplated surface,and measuring the time required to penetrate the coating andexpose the substrate; this time is proportional to the coatingthickness.4. Significance and Use4.1 The thickness of a metal coating is often critical to itsperformance.4.2 This
8、 procedure is useful for an approximate determina-tion when the best possible accuracy is not required. For morereliable determinations, the following methods are available:Test Methods B487, B499, B504, and B568.4.3 This test assumes that the rate of dissolution of thecoating by the corrosive reage
9、nt under the specified conditionsis always the same.5. Factors Affecting the Accuracy5.1 The following factors will affect the accuracy of acoating thickness measurement made by this method:5.1.1 Cleanliness of SurfaceAny foreign material on thesurface to be tested, including lacquer, grease, corros
10、ionproducts, and conversion coatings, will interfere with the testand must be removed. Tarnish and conversion coatings canoften be removed by mild burnishing with a soft, clean pencileraser.5.1.2 Concentration of Test SolutionVariation from thestated concentrations will introduce an error unless the
11、 thick-ness factor is adjusted accordingly. Test solutions cannot bereused.5.1.3 TemperatureThe thickness factor for a givensolution, being a function of the temperature, must be knownfor the temperature at which the test is made. Specimens to betested should be allowed to reach room temperature bef
12、oretesting.5.1.4 Dropping RateThe thickness factor is also a func-tion of the dropping rate. The thickness factors given in Section1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.10 on TestMethods.Curr
13、ent edition approved May 1, 2012. Published November 2013. Originallyapproved in 1971. Last previous edition approved in 2007 as B555 86 (2007).DOI: 10.1520/B0555-86R12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annua
14、l Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Such tests were described by Hull, R. O., and Strausser, P., Monthly Review,American Electroplaters Society, MRAEA, Vol 22, 1935, p. 9, and by Brenner, A.,Proceedings, American Electroplaters
15、 Society, AEPPB, Vol 27, 1939, p. 204.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States110 are for a dropping rate of 100 drops/min and will remainvalid for the range of 95 to 105 drops/min.5.1.5 Solution DrainageThe thickness factors g
16、iven inSection 10 are valid only if the test solution is rapidly drainedoff, as from a flat surface inclined 45 from the horizontal. Thetest cannot be made on a horizontal surface or at a location thatdoes not permit rapid drainage.5.1.6 Drop SizeVariation in drop size may alter thepenetration rate.
17、 The tip of the dropping apparatus shouldconform to the dimensions given in Fig. 1 and should be keptclean.5.1.7 Alloy LayerThe presence of an alloy layer at thecoating-substrate interface may obscure the end point andintroduce an uncertainty as to the amount of alloy included inthe thickness measur
18、ement.5.1.8 Detection of End PointThe end point (the time atwhich the coating has been penetrated and the substrateexposed) is characterized by a change in the appearance of thesurface on which drops are falling. This is a matter of personaljudgment and may not always be clearly defined, dependingup
19、on the coating-substrate combination and the extent ofalloying, if any. Such errors may be minimized by standardiz-ing the test method with identical specimens with a knowncoating thickness determined by other means.5.1.9 Composition of CoatingThe dropping tests de-scribed in this document are inten
20、ded for use on nominally“pure” coatings. The thickness factors listed in Section 10 areexpected to vary with gross variations in the composition of thecoating, as might result from codeposition of an alloyingcomponent. The specific effects, on the thickness factors, ofAGlass tube with one end open t
21、o atmosphere and one end submerged in the testsolution in funnel, C.BRubber stopper forms air tight seal between tube, A, and funnel, C.CSeparatory funnel.DWide-bore rubber tubing (75 to 125 mm in length) or sealed glass joints.ECapillary tubing (140 mm in length, 0.64-mm bore).FRubber tubing or sea
22、led glass joints.GCapillary glass tip (with 12.7-mm taper to outside diameter of 3.5 mm).HSpecimen.ICollector of spent solution.NOTE 1Solution head is constant as long as air is being drawn through tube, A.FIG. 1 Dropping FunnelB555 86 (2012)2impurities or of inclusions from brighteners or other add
23、itionagents can be appreciable. Uncertainty from these sources maybe minimized by standardizing the test method againststandards, prepared from the same type of plating solution, thethicknesses of which have been determined by other methods.6. Apparatus6.1 Fig. 1 illustrates one form of apparatus us
24、ed for drop-ping tests. Equivalent apparatus are commercially available, asis a solenoid operated unit with a digital readout.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in the preparation of all test solutions.7.2 Purity of WaterWater used in the preparation
25、of testsolutions shall be reagent water as defined in SpecificationD1193.8. Test Solutions8.1 Solution for Cadmium and Zinc:Chromic acid (CrO3) 200 g/LSulfuric acid (96 % H2SO4, sp gr 1.84) 50 g/L or 27 mL/LNOTE 2Sulfuric acid is added slowly with stirring to at least 20 timesits volume of water.8.2
26、 Solution for Cadmium only:Ammonium nitrate (NH4NO3) 110 g/LHydrochloric acid (37 % HCl, sp gr 1.19) 10 mL/L8.3 Solution for Zinc only:Ammonium nitrate (NH4NO3) 100 g/LNitric acid (70 % HNO3, sp gr 1.42) 55 mL/L8.4 Solution for Tin:Trichloroacetic acid (CHCl3COOH) 100 g/L8.5 Solution for Copper:Hydr
27、ochloric acid (37 % HCl sp gr 1.19) 200 mL/LAntimony trioxide (Sb2O3)20g/LGlacial acetic acid (99.7 % CH3COOH) 250 mL/LFerric chloride (FeCl36H2O) 450 g/LNOTE 3For ease of preparation, dissolve the antimony trioxide in thehydrochloric acid, add 150 mL of water and the glacial acetic acid, andthen ad
28、d the ferric chloride in small portions. Finally dilute to 1.00 L withwater.NOTE 4Variations of 62 % in the composition of a test solution arepermissible.9. Procedure9.1 Clean the specimen and allow it and the test solution toreach room temperature, which should be recorded. Supportthe specimen so t
29、hat the surface to be tested makes a 45 anglewith the horizontal, about 13 mm below the tip of the droppingapparatus. Drop the test solution onto the specimen at a rate of100 drops/min. Note and record the time required for thesolution to penetrate the coating at the point on which the dropsfall.10.
30、 Computation of Thickness10.1 Multiply the time required to penetrate the coating byan appropriate thickness factor to obtain the coating thickness.10.2 Below are the thickness factors, applicable to nomi-nally “pure” coatings (5.1.9), for the solutions given in Section8. They are valid for a droppi
31、ng rate of 100 drops/min from acapillary tip, the dimensions of which are given in Fig. 1.Cadmium (chromic acid solution): 0.35 m/sZinc (chromic acid solution): 0.26 m/sCadmium (nitrate solution): 0.25 m/sZinc (nitrate solution): 0.25 m/sTin 0.25 m/sCopper 0.13 m/s10.2.1 The first two thickness fact
32、ors for cadmium and zincand the chromic acid solution are only valid for a temperatureof 24C; the factors for these metals and this test solution atother temperatures are given in Fig. 2 and Fig. 3.10.2.2 The last four thickness factors are valid for tempera-tures in a range from 20 to 30C.11. Repro
33、ducibility and Accuracy11.1 The reproducibility for a single operator is estimated tobe 62 drops (equivalent to 1.2 s) or 65 %, whichever isgreater.11.2 The over-all accuracy may be substantially poorer thanthe reproducibility, because of the uncertainties discussed inSection 5, and will depend upon
34、 the control exercised over thevariables. For maximum accuracy, the test method should bestandardized with specimens identical to those being tested,having known coating thicknesses determined by other meth-ods. Sometimes a chemical can be added to the droppingsolution to aid in determining the end
35、point, for example,potassium ferricyanide (K3Fe(CN)6) has been added to the testsolution for zinc in 8.3.B555 86 (2012)3FIG. 2 Chart for Determining Thickness of Zinc Coating by the Chromic Acid Dropping TestB555 86 (2012)4ASTM International takes no position respecting the validity of any patent ri
36、ghts asserted 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 an
37、y time by 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 w
38、ill receive 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 A
39、STM 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. 3 Chart for Determining Thickness of Cadmium Coating by the Chromic Acid Dropping TestB555 86 (2012)5
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