1、Designation: B767 88 (Reapproved 2016)Standard Guide forDetermining Mass Per Unit Area of Electrodeposited andRelated Coatings by Gravimetric and Other ChemicalAnalysis Procedures1This standard is issued under the fixed designation B767; the number immediately following the designation indicates the
2、 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide outlines a general method for determinin
3、gthe 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 method
4、s 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 physica
5、lmeans 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 coa
6、ting 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 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of
7、 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 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A90/A90M Test Method for
8、 Weight Mass of Coating onIron and Steel Articles with Zinc or Zinc-Alloy CoatingsA309 Test Method for Weight and Composition of Coatingon Terne Sheet by the Triple-Spot Test (Withdrawn 2015)3A428/A428M Test Method for Weight Mass of Coating onAluminum-Coated Iron or Steel ArticlesB137 Test Method f
9、or Measurement of Coating Mass PerUnit Area on Anodically Coated AluminumB449 Specification for Chromates on Aluminum2.2 British Standards Institution Documents:4BS 729 Hot Dip Galvanized Coatings on Iron and SteelArticles, Specification forBS 1706 Electroplated Coatings of Cadmium and Zinc onIron a
10、nd Steel, Specification forBS 1872 Electroplated Coatings of Tin, Specification forBS 3189 Phosphate Treatment of Iron and Steel, Specifica-tion forBS 3382 Electroplated Coatings on Threaded Components,Specification forBS 3597 Electroplated Coatings of 65/35 Tin-Nickel Alloy,Specification for2.3 Gov
11、ernment Standards:2.3.1 DOD Standard:5DOD-P-16232F Phosphate Coatings, Heavy, Manganese orZinc Base (for Ferrous Metals)2.3.2 Federal Standards:6FED-STD 151b Metals; Test Methods: Test 513.1 for Weightof Coating on Hot Dip Tin Plate and Electrolytic Tin Plate1This guide is under the jurisdiction of
12、ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.10 on TestMethods.Current edition approved Nov. 1, 2016. Published November 2016. Originallyapproved in 1987. Last previous edition approved in 2010 as B767 88 (2010).DOI: 10.1520/B0767-88R16.2F
13、or 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.3The last approved version of this historical standard is refer
14、enced onwww.astm.org.4Available from British Standards Institute (BSI), 389 Chiswick High Rd.,London W4 4AL, U.K.5Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098.6Available from U.S. Government Printing Office Superintende
15、nt of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1RR-T-51D Tableware and FlatwareSilverplated2.3.3 Military Standard:5MIL-M-45202C Magnesium Alloys, Anodic Tre
16、atment of2.4 ISO Standards:7ISO 2081 Metallic CoatingsElectroplated Coatings ofZinc on Iron or SteelISO 2082 Metallic CoatingsElectroplated Coatings onCadmium on Iron or SteelISO 2093 Metallic CoatingsElectrodeposited Coatings ofTin, Annex BISO 2106 Anodizing of Aluminum and its AlloysDetermination
17、of Mass Per UnitArea (Surface Density) ofAnodic Oxide CoatingsGravimetric MethodISO 3892 Conversion Coatings on Metallic MaterialsDetermination of Coating Mass Per Unit AreaGravimetric MethodsISO 4522/1 Metallic CoatingsTest Methods for Electrode-posited Silver and Silver Alloy CoatingsPart 1: Deter
18、-mination of Coating ThicknessISO 4524/1 Metallic CoatingsTest Methods for Electrode-posited Gold and Gold Alloy CoatingsPart 1: Determi-nation 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 befor
19、e and after dissolvingthe coating in a reagent that does not attack the substrate.3.1.2 Weighing the coating after dissolving the substrate 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 m
20、ass per unit area is calculated from the mass andarea measurements, the thickness from the mass, area, anddensity of the coating materials.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 proced
21、ures are used for acceptance testing andappear in a few specifications.4.3 Coating thickness instruments are often calibrated withthickness 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
22、 only if the densityof the coating material is known.5. Apparatus5.1 In addition to normal chemical laboratory equipment forhandling small 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 Siz
23、eThe specimen must be large enough to permit areaand mass measurement of adequate accuracy. (See Section 7and 8.2.)6.2 ShapeThe shape of the 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 are
24、a to be measured is small andneeds to be known accurately, the edges must be dressed toremove smeared coating, to remove loose burrs, and to providewell-defined and (for rectangles) straight edges. This should beconsidered for areas less than 100 mm2. One method ofdressing the edges of a rectangular
25、 specimen is to clamp thespecimen between two plastic or metal blocks with the edge ofthe specimen flush with the edges of the blocks and then togrind and polish the edges metallographically.6.4 Heat TreatmentIf the substrate is to be dissolvedleaving the coating intact, it is desirable to first hea
26、t-treat thetest specimen so that the coating will not curl up tightly or fallapart. Some gold deposits of 1.5 mg/cm2will fall apart whentheir 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
27、 being determined, oneshould not use a heat treatment that might change the densityof the coating material.7. Measurement of Coated Area:7.1 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 meas
28、uring thearea will depend on the desired accuracy and the specimensize.7.2 EquipmentThe area can be measured with aplanimeter, but it is usually determined by linear measure-ments. Often a micrometer or vernier caliper is used. For largeareas, however, a ruler may do. For maximum accuracy, ameasurin
29、g microscope is used.7.3 Number of MeasurementsBecause circular or rectan-gular specimens will not be perfectly circular or rectangular, itis 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
30、obtain an average foreach dimension.NOTE 1In the case of a cylinder one would normally measure thediameter and length. In one specification 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,
31、and the density ofthe steel substrate. (l =mr2D)8. Gravimetric Determination of Mass of Coating:8.1 Specimen SizeThe accuracy of the mass 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 wei
32、ghed with the desiredaccuracy.8.2 EquipmentA balance is required, but the requiredsensitivity of the balance depends on the size of the test7Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.B767 88 (2016)2specimen, the coating thickness (coati
33、ng 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 islimited to small samples.9. Procedure9.1 T
34、he 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 (see AnnexA1) and weighing the coating directly.9.1.1 By DifferenceThe test specimen is first cleaned ofany fore
35、ign material and finally rinsed with alcohol, blown drywith clean air, and weighed. The specimen is immersed in theappropriate reagent (see Annex A1) to dissolve the coating,rinsed with water, rinsed with alcohol, blown dry with cleanair, and weighed again. The loss of mass is the mass of thecoating
36、. 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 any dissolution of the substrate with the coating during t
37、hestripping 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 dissolution of thecoating, submit the isolated coating to the sam
38、e 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 coating with thesubstrate during the stripping process.NOTE 2
39、The 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 and substrate are dissolved in a suitable reagent andthe
40、n 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.10. Calculation10.1 Calculate the mass per unit area as
41、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 3M/D m! (2)where:M = mass per unit area (mg/cm2), andD = density (g/cm3).NOTE 3The density of a coating metal is usually not the same
42、 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. Safranek.8ANNEX(Mandatory Information)A1. REAGENTS FOR SELECTI
43、VE 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.A1.1With many of the reagents given in TableA1.1, there may besome dissolution of the layer
44、 other than the one being stripped.Often the dissolution is not significant, but the possibilityshould be tested for as suggested in 9.1.1, and 9.1.2.A1.2Dissolution is carried out at room temperature unless other-wise indicated. All test pieces are rinsed and dried (see 9.1.1and 9.1.2) before weigh
45、ing.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 remove loose material. Drain off water, immerse3sinconcentra
46、ted 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 A428/A428M.aluminum steel (1) 200 g SbCl3in 1L concentrate
47、d HCl Mix equal volume of (1) and (2), immerse until evolution of hydrogen stops,about 14 min.8Printed in The Properties of Electrodeposited Metals and Alloys, SecondEdition, American Electroplaters and Surface Finishers Society, 1986.B767 88 (2016)3TABLE A1.1 ContinuedCoating Substrate Reagents Rem
48、arksSources(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 in Ref (1) and in the 1981 issue of TestMethod A428/A428M.Aanodized aluminum aluminum 35 mL 85 % phosphoric acid plus 20 g/LCrO3Immerse 5 min
49、at 100C, rinse, dry, weigh. Repeat cycle until weight isconstant.This procedure appears in the 1945 issue of Test Method B137 and the1982 issue of ISO Standard 2106.anodized magnesium(HAE)magnesium 300 g/L CrO3Immerse at room temperature, rinse, dry, weigh, 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 H2SO4cadm
