1、Designation: B 767 88 (Reapproved 2006)Standard Guide forDetermining Mass Per Unit Area of Electrodeposited andRelated Coatings by Gravimetric and Other ChemicalAnalysis Procedures1This standard is issued under the fixed designation B 767; the number immediately following the designation indicates t
2、he year oforiginal adoption 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.1. Scope1.1 This guide outlines a general method for determi
3、ningthe mass per unit area of electrodeposited, electroless,mechanically-deposited, vacuum-deposited, anodicoxide, andchemical conversion coatings by gravimetric and other chemi-cal analysis procedures.1.2 This guide determines the average mass per unit areaover a measured area.1.3 The stripping met
4、hods cited are described in specifica-tions or in the open literature or have been used routinely by atleast one laboratory.1.4 The procedures outlined can be used for many coating-substrate combinations. They cannot be used where the coatingcannot be separated from the substrate by chemical or phys
5、icalmeans as would be the case if white brass were plated withyellow brass.1.5 In principle, these procedures can be used to measurevery thin coatings or to measure coatings over small areas, butnot thin coatings over small areas. The limits depend on therequired accuracy. For example, 2.5 mg/cm2of
6、coating mightrequire 2.5 mg of coating covering 1 cm2, but 0.1 mg/cm2ofcoating would require 25 cm2to obtain 2.5 mg of coating.1.6 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 a
7、ppro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 90/A 90M Test Method for Weight Mass of Coating onIron and Steel Articles with Zinc or Zinc-Alloy CoatingsA 309 Test Method for Weight and Comp
8、osition of Coatingon Terne Sheet by the Triple-Spot TestA 428/A 428M Test Method for Weight Mass of Coatingon Aluminum-Coated Iron or Steel ArticlesB 137 Test Method for Measurement of Coating Mass PerUnit Area on Anodically Coated AluminumB 449 Specification for Chromates on Aluminum2.2 British Sta
9、ndards Institution Documents:3BS 729 Hot Dip Galvanized Coatings on Iron and SteelArticles, Specification forBS 1706 Electroplated Coatings of Cadmium and Zinc onIron and Steel, Specification forBS 1872 Electroplated Coatings of Tin, Specification forBS 3189 Phosphate Treatment of Iron and Steel, Sp
10、ecifica-tion forBS 3382 Electroplated Coatings on Threaded Components,Specification forBS 3597 Electroplated Coatings of 65/35 Tin-Nickel Alloy,Specification for2.3 Government Standards:2.3.1 DOD Standard:4DOD-P-16232F Phosphate Coatings, Heavy, Manganese orZinc Base (for Ferrous Metals)2.3.2 Federa
11、l Standards:5FED-STD 151b Metals; Test Methods: Test 513.1 forWeight of Coating on Hot Dip Tin Plate and ElectrolyticTin PlateRR-T-51D Tableware and FlatwareSilverplated2.3.3 Military Standard:4MIL-M-45202C Magnesium Alloys, Anodic Treatment of2.4 ISO Standards:6ISO 2081 Metallic CoatingsElectroplat
12、ed Coatings ofZinc on Iron or SteelISO 2082 Metallic CoatingsElectroplated Coatings onCadmium on Iron or Steel1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.10 on TestMethods.Current edition approved
13、April 1, 2006. Published April 2006. Originallyapproved in 1987. Last previous edition approved in 2001 as B 767 88 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, re
14、fer to the standards Document Summary page onthe ASTM website.3Available from British Standards Institute (BSI), 389 Chiswick High Rd.,London W4 4AL, U.K.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098.5Available from U.S
15、. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.6Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
16、shohocken, PA 19428-2959, United States.ISO 2093 Metallic CoatingsElectrodeposited Coatings ofTin, Annex BISO 2106 Anodizing of Aluminum and its AlloysDetermination of Mass Per UnitArea (Surface Density) ofAnodic Oxide CoatingsGravimetric MethodISO 3892 Conversion Coatings on Metallic MaterialsDeter
17、mination of Coating Mass Per Unit AreaGravimetric MethodsISO 4522/1 Metallic CoatingsTest Methods for Elec-trodeposited Silver and Silver Alloy CoatingsPart 1:Determination of Coating ThicknessISO 4524/1 Metallic CoatingsTest Methods for Elec-trodeposited Gold and Gold Alloy CoatingsPart 1:Determina
18、tion of Coating Thickness3. Summary of Guide3.1 The mass of a coating over a measured area is deter-mined by the following:3.1.1 Weighing the test specimen before and after dissolvingthe coating in a reagent that does not attack the substrate.3.1.2 Weighing the coating after dissolving the substrate
19、 ina reagent that does not attack the coating, or3.1.3 Dissolving both the coating and the substrate andquantitatively analyzing the resulting solution.3.2 The mass per unit area is calculated from the mass andarea measurements, the thickness from the mass, area, anddensity of the coating materials.
20、4. Significance and Use4.1 The thickness of a coating is critical to its performanceand is specified in many specifications calling for coatings.4.2 These procedures are used for acceptance testing andappear in a few specifications.4.3 Coating thickness instruments are often calibrated withthickness
21、 standards that are based on mass and area measure-ments.4.4 The average thickness of a coating on the measured areacan be calculated from its mass per unit area only if the densityof the coating material is known.5. Apparatus5.1 In addition to normal chemical laboratory equipment forhandling small
22、amounts of corrosive and toxic chemicals, anaccurate ruler or vernier caliper and a good balance arerequired. See Sections 7 and 8.6. Specimen Preparation6.1 SizeThe specimen must be large enough to permitarea and mass measurement of adequate accuracy. (See Section7 and 8.2.)6.2 ShapeThe shape of th
23、e test specimen must be suchthat the surface area can be easily measured. A rectangular orcircular test specimen is usually suitable.6.3 Edge ConditionIf the area to be measured is small andneeds to be known accurately, the edges must be dressed toremove smeared coating, to remove loose burrs, and t
24、o providewell-defined and (for rectangles) straight edges. This should beconsidered for areas less than 100 mm2. One method ofdressing the edges of a rectangular specimen is to clamp thespecimen between two plastic or metal blocks with the edge ofthe specimen flush with the edges of the blocks and t
25、hen togrind and polish the edges metallographically.6.4 Heat TreatmentIf the substrate is to be dissolvedleaving the coating intact, it is desirable to first heat-treat thetest specimen so that the coating will not curl up tightly or fallapart. Some gold deposits of 1.5 mg/cm2will fall apart whenthe
26、ir substrates are dissolved, but after heat treatment at 120Cfor 3 h will support themselves. If the thickness of a coating(instead of its mass per unit area) is being determined, oneshould not use a heat treatment that might change the densityof the coating material.7. Measurement of Coated Area:7.
27、1 Measurement MethodThe accuracy of the area mea-surement must be better than the desired accuracy of the massper unit area measurement. Hence the method of measuring thearea will depend on the desired accuracy and the specimensize.7.2 EquipmentThe area can be measured with a planime-ter, but it is
28、usually determined by linear measurements. Oftena micrometer or vernier caliper is used. For large areas,however, a ruler may do. For maximum accuracy, a measuringmicroscope is used.7.3 Number of MeasurementsBecause circular or rectan-gular specimens will not be perfectly circular or rectangular, it
29、is desirable to measure each dimension in three places. For arectangle, one would measure the length of each edge and thelength and width through the center and obtain an average foreach dimension.NOTE 1In the case of a cylinder one would normally measure thediameter and length. In one specification
30、 for galvanized wire (fencing), thelength of the wire specimen is not measured, but in effect is calculatedfrom the mass (which is measured anyway), the radius, and the density ofthe steel substrate. (l =m/pr2D)8. Gravimetric Determination of Mass of Coating:8.1 Specimen SizeThe accuracy of the mass
31、 measurementmust be better than the desired accuracy of the mass per unitarea measurement. Hence, the test specimen must be largeenough that the coating can be weighed with the desiredaccuracy.8.2 EquipmentA balance is required, but the requiredsensitivity of the balance depends on the size of the t
32、estspecimen, the coating thickness (coating mass), and the re-quired accuracy of the measurement. A balance that weighs to0.01 g is sometimes satisfactory, though a good analyticalbalance weighing to 0.0001 g is more versatile.Amicrobalanceis required for small specimens of thin coatings, but it isl
33、imited to small samples.9. Procedure9.1 The mass of coating may be determined: (1) by weigh-ing the test specimen before and after dissolving the coating(see Annex A1) and taking the difference, or (2) by dissolvingthe substrate (seeAnnexA1) and weighing the coating directly.9.1.1 By DifferenceThe t
34、est specimen is first cleaned ofany foreign material and finally rinsed with alcohol, blown drywith clean air, and weighed. The specimen is immersed in theB 767 88 (2006)2appropriate reagent (see Annex A1) to dissolve the coating,rinsed with water, rinsed with alcohol, blown dry with cleanair, and w
35、eighed again. The loss of mass is the mass of thecoating. To determine if there was any dissolution of thesubstrate, repeat the process with the stripped substrate makingsure that it is in the reagent just as long as before. Any loss ofmass enables one to make a judgment of a possible error dueto an
36、y dissolution of the substrate with the coating during thestripping process.9.1.2 By Direct WeighingThe substrate is dissolved in theappropriate reagent (see Annex A1). The coating is rinsed withwater, rinsed with alcohol, blown dry with clean air, andweighed. To determine if there was any dissoluti
37、on of thecoating, submit the isolated coating to the same strippingprocess making sure that the coating is in the stripping reagentfor the same length of time as it was during the strippingprocess. Any loss of mass enables one to make a judgment ofa possible error due to any dissolution of the coati
38、ng with thesubstrate during the stripping process.NOTE 2The test procedure given at the end of 9.1.1 and 9.1.2 shouldbe conducted to evaluate a gravimetric method the first time it is used.9.2 Determination of Mass of Coating by ChemicalAnalysisThis method is by nature very general. Both thecoating
39、and substrate are dissolved in a suitable reagent andthen the resulting solution is analyzed for the coating material.For each coating-substrate-reagent combination, there are sev-eral analytical methods. For possible analytical methods seeVolumes 03.05 and 03.06 of the Annual Book of ASTMStandards.
40、10. Calculation10.1 Calculate the mass per unit area as follows:Mass per unit area 5 m/A mg/cm2! (1)where:m = mass of coating (mg), andA = area covered by coating (cm2)10.2 Calculate the thickness as follows:Thickness 5 10 3 M/D m! (2)where:M = mass per unit area (mg/cm2), andD = density (g/cm3).NOT
41、E 3The density of a coating metal is usually not the same as thehandbook value or the theoretical value. For example, the density ofelectrodeposited gold is generally less than 19.3 g/cm3and sometimes aslow or lower than 17 g/cm3. The densities of some electrodeposited metalsare given by W. H. Safra
42、nek.7ANNEX(Mandatory Information)A1. REAGENTS FOR SELECTIVE DISSOLUTION OF METAL LAYERSNOTE A1.1The specific issues of standards are cited in this table andincluded in the literature as references because they contain the informa-tion from which this table is based.A1.1 With many of the reagents giv
43、en in Table A1.1, theremay be some dissolution of the layer other than the one beingstripped. Often the dissolution is not significant, but thepossibility should be tested for as suggested in 9.1.1, and 9.1.2.A1.2 Dissolution is carried out at room temperature unlessotherwise indicated. All test pie
44、ces are rinsed and dried (see9.1.1 and 9.1.2) before weighing.TABLE A1.1 ReagentsCoating Substrate Reagents RemarksSourcesaluminum steel (1) 20 parts by massNaOH, 80 partswater(2) concentrated HCl (sp gr 1.19)Immerse a few min (avoid longer time) at about 90C. While rinsing, scrubwith a sponge to re
45、move loose material. Drain off water, immerse3sinconcentrated HCl at room temperature, scrub again in running water, andrepeat entire process until there is no visible reaction in the HCl. Two orthree cycles are required normally. A more detailed description is given inthe 1981 issue of Test Method
46、A 428/A 428M.aluminum steel (1) 200 g SbCl3in 1L concentrated HCl Mix equal volume of (1) and (2), immerse until evolution of hydrogen stops,about 14 min.(2) 100 g SnCl2.2H2O in 1L concentrated Keep below 38C, rinse and scrub with soft cloth.HCl plus a few granules of tin This test procedure appears
47、 in Ref (1) and in the 1981 issue of TestMethod A 428/A 428M.Aanodized aluminum aluminum 35 mL 85 % phosphoric acid plus 20 g/LCrO3Immerse 5 min at 100C, rinse, dry, weigh. Repeat cycle until weight isconstant.This procedure appears in the 1945 issue of Test Method B 137 and the1982 issue of ISO Sta
48、ndard 2106.7Printed in The Properties of Electrodeposited Metals and Alloys, SecondEdition, American Electroplaters and Surface Finishers Society, 1986.B 767 88 (2006)3Coating Substrate Reagents RemarksSourcesanodized magnesium(HAE)magnesium 300 g/L CrO3Immerse at room temperature, rinse, dry, weigh
49、, and repeat until weightloss is less than 3.9 mg/dm2. Keep piece of commercially pure aluminum insolution but not in contact with magnesium.This procedure appears in Military Standard MIL-M-45202C.brass steel 500 g/L CrO3Immerse at room temperature with mild agitation.50 g/L H2SO4cadmium steel 300 g/L NH4NO3Immerse.This procedure appears in the 1961 issue of British Standard 3382 and the1986 issue of ISO Standard 2082.cadmium steel 20g Sb2O3in 1L concentrated HCl or 20g Immerse until evolution of gas practically stops. (2)Sb2O3in 800 mL c
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