1、Designation: A90/A90M 11Standard Test Method forWeight Mass of Coating on Iron and Steel Articles withZinc or Zinc-Alloy Coatings1This standard is issued under the fixed designation A90/A90M; the number immediately following the designation indicates the yearof original adoption or, in the case of r
2、evision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test metho
3、d covers procedures for determining theweight mass of coating on iron or steel sheet, wire, and otherarticles in which the coating is zinc or a zinc alloy, such aszinc-5 % aluminum (including zinc-5 % aluminum-mischmetal and zinc-5 % aluminum-0.1 % magnesium), zinc-aluminum-magnesium (including zinc
4、-5 to 9 % aluminum-magnesium and zinc-9 to 13 % aluminum-magnesium) or 55 %aluminum-zinc. In the body of this test method, reference tozinc coating shall be interpreted to also include zinc alloycoating except where specifically stated otherwise.1.2 The final results determined by this test method s
5、hall beexpressed in inch-pound units or SI units, depending on theunits used in the material specification to which the results areto be compared. Certain portions of the procedure involvingdetermination of specimen weight mass have traditionallybeen performed in SI units, and corresponding inch-pou
6、ndunits are not included.1.3 For sheet products, the final results are expressed aseither coating weight mass total both sides, or coating weightmass separately on each side, depending on the specifiedrequirements.1.4 This standard does not purport to address all of thesafety concerns, if any, assoc
7、iated 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. For specific hazardsstatements see 5.1.2. Referenced Documents2.1 ASTM Standards:2A653/A653M Specifi
8、cation for Steel Sheet, Zinc-Coated(Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed)by the Hot-Dip ProcessA792/A792M Specification for Steel Sheet, 55 %Aluminum-Zinc Alloy-Coated by the Hot-Dip ProcessA875/A875M Specification for Steel Sheet, Zinc-5 % Alu-minum Alloy-Coated by the Hot-Dip Proces
9、sA1046/A1046M Specification for Steel Sheet, Zinc-Aluminum-Magnesium Alloy-Coated by the Hot-Dip Pro-cessA1063/A1063M Specification for Steel Sheet, Twin-RollCast, Zinc-Coated (Galvanized) by the Hot-Dip ProcessD1193 Specification for Reagent WaterE29 Practice for Using Significant Digits in Test Da
10、ta toDetermine Conformance with Specifications3. Significance and Use3.1 This test method provides a standard method for deter-mining the weight mass of coating for comparison withspecification requirements. A coating of zinc on iron or steelarticles provides protection against corrosion.As the prot
11、ectionis provided by sacrificial loss of zinc, the degree of protectionis proportional to the weight mass of zinc coating. Specifi-cations for zinc-coated articles frequently provide for differentclasses of coating so that the purchaser can select the coatingweight mass most suitable to his needs.4.
12、 Reagents4.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other g
13、rades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.1This test method is under the jurisdiction of ASTM Committee A05 onMetallic-Coated Iron and Steel Products and is the direct respons
14、ibility ofSubcommittee A05.07 on Methods of Testing.Current edition approved Nov. 1, 2011. Published November 2011. Originallyapproved in 1923. Last previous edition approved in 2009 as A90/A90M - 09. DOI:10.1520/A0090_A0090M-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, o
15、rcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3“Reagent Chemicals, American Chemical Society Specifications,” Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing o
16、f reagents not listed bythe American Chemical Society, see “Analar Standards for Laboratory U.K.Chemicals,” BDH Ltd., Poole, Dorset, and the “United States Pharmacopeia.”1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C70
17、0, West Conshohocken, PA 19428-2959, United States.4.2 Purity of WaterWater used to prepare chemical solu-tions shall be reagent water as defined by Type IV ofSpecification D1193.4.3 Antimony Trichloride Solution Dissolve 20 g ofSb2O3or 32 g of SbCl3in 1000 mL of HCl (sp gr 1.18 to 1.19).4.4 Hydroch
18、loric Acid (sp gr 1.18 to 1.19)Concentratedhydrochloric acid (HCl).4.5 Hydrochloric AcidAntimony Trichloride SolutionAdd 5 mL of antimony trichloride solution to 100 mL of HCl(sp gr 1.18 to 1.19).4.6 Hydrochloric Acid (1 + 1)Mix 500 mL of HCl (sp gr1.18 to 1.19) with 500 mL of reagent water and cool
19、 to roomtemperature.4.7 Sulfuric Acid (25 + 75)Mix 250 mL of H2SO4(sp gr1.84) with 750 mL of reagent water and cool to roomtemperature.NOTE 1It is advisable to use an inhibitor with acid solution (forexample, Hexamethylamine Tetramine or similar) at the concentrationlevel according to the manufactur
20、ers recommendations to prevent attackof the substrate.5. Hazards5.1 WarningSmall amounts of the poisonous gas stibine(SbH3) may be evolved during the stripping process using thehydrochloric acid-antimony trichloride method. Hydrochloricacid fumes are present, and hydrogen gas is evolved in thestripp
21、ing process. Therefore, the test should be performedunder conditions of adequate ventilation. A fume hood isrecommended for large numbers of samples or where the test isto be carried out frequently over extended periods of time.5.2 WarningMixing of sulfuric acid with water couldresult in severe inju
22、ries if not properly done. Mixing must bedone by slowly adding sulfuric acid to water due to the heatgenerated and possible splashing. Under no circumstancesshould the water be added to the acid. The mixing should beperformed under an acid fume hood.6. Sampling6.1 Zinc-Coated SheetsSamples for weigh
23、t mass ofcoating determination shall be secured in accordance withSpecifications A653/A653M, A792/A792M, A875/A875M,A1046/A1046M,orA1063/A1063M depending on the type ofcoating.NOTE 2For convenience in calculating test results in inch-poundunits, the specimen should have an area of 5.08 in.2of sheet
24、(2.25 60.01-in. square or 2.54 6 0.01 in. in diameter). The weight mass ofcoating in grams on a specimen of that area is numerically equal to theweight mass of coating in ounces per square foot of sheet. For results tobe reported in metric units, the specimen should have an area of 3330 mm2of sheet
25、(57.7 6 0.1-mm square or 65.1 6 0.1 mm in diameter).6.2 Zinc-Coated WireSamples shall be secured as desig-nated in the appropriate specification. The specimen of wiremay be of any length over 12 in. 305 mm, but preferablyabout 24 in. 609 mm. Where a continuous length is notavailable, shorter lengths
26、 totaling over 12 in. 300 mm, butpreferably about 24 in. 600 mm, shall be used. Since thedensity of the steel is known 0.283 lb/in.37830 kg/m3, it is notnecessary to use a specific length of specimen.6.3 Zinc-Coated Articles Other Than Sheet or WireSamples for weight mass of coating determination sh
27、all besecured as designated in the appropriate specification. Exceptas otherwise provided, the specimens should have a minimumarea of 3 in.2(2000 mm2) of zinc-coated surface. For very smallitems, several pieces may have to be stripped to obtain theminimum area.6.3.1 In the case of threaded articles,
28、 such as bolts andscrews, the determination shall be made on a portion of thearticles that does not include any thread.7. Procedure7.1 Strip the zinc coating from the specimens by using oneof the following methods: hydrochloric acid (1 + 1), hydro-chloric acid-antimony trichloride solution, or sulfu
29、ric acid (25+ 75). For zinc alloy coatings containing less than 90 % zinc,the stripping shall be done using hydrochloric acid (1 + 1) orsulfuric acid (25 + 75).7.2 Clean the specimens by washing with solvent naphtha orother suitable solvent, then rinse with alcohol, and dry thor-oughly.7.3 Determine
30、 the weight mass of the specimens individu-ally to the nearest 0.01 g, except for articles other than sheet orwire with a specimen weight mass greater than 125 g,determine the weight mass to at least the nearest 0.1 g. Afterdetermining the weight mass, immerse each specimen singlyin the stripping so
31、lution and allow to remain until the violentevolution of hydrogen has ceased, and only a few bubbles arebeing evolved. This requires about 15 to 30 s, except in thecase of sherardized coatings, which require a somewhat longertime. The same solution may be used repeatedly until the timerequired for s
32、tripping becomes inconveniently long. The tem-perature of the stripping solution shall at no time exceed 100F38C. After stripping, wash the specimens by scrubbing themunder running water, dip in hot water, and wipe or blow dry.Determine the weight mass of the specimens again, to thesame precision as
33、 in the initial determination.7.4 Sheet SpecimensWhen measuring the total coatingweight mass on both sides, or the single side coating weightmass on each side, determine the area of sheet (one surface)to the nearest 0.01 in.25 mm2. If specimens were prepared tothe dimensions as provided in Note 2, t
34、hey shall be presumedto have an area of 5.08 in.23330 mm2. When it is not possibleto determine the area accurately, as in specimens from corru-gated sheets, the thickness of the stripped sheet shall bedetermined to the nearest 0.001 in. 0.01 mm.7.4.1 When determining the coating weight mass on onesi
35、de of sheet material, use the procedure described in 7.3,except use a “stop-off” to protect one side from the strippingmedium. Acid-resistant paints or lacquers, acid-resistant tape,or mechanical devices fastened to the test specimen areexamples of commonly used “stop-off” materials. Apply the“stop-
36、off” to the specimen after the initial determination ofweight mass and remove before the second determination ofweight mass. Because of the possibility of moisture absorp-tion during the stripping process, the “stop-off” must not be onthe specimen during either weight mass determinations.Determine t
37、he coating weight mass on the second sidesubsequently without a “stop-off” on the first side.A90/A90M 1127.5 Wire SpecimensDetermine the diameter of thestripped wire to the nearest 0.001 in. 0.01 mm by taking theaverage of two measurements at right angles to each other.7.6 Specimens Other Than Sheet
38、 or Wire Determine thetotal coated area of the original specimen to the nearest 0.01in.25 mm2. Alternatively, for specimens of uniform thicknessof base metal, such as a piece of plate or pipe, determine theaverage thickness of the stripped specimen to the nearest 0.001in. 0.01 mm.8. Calculation8.1 Z
39、inc-Coated Sheet:8.1.1 Results in Inch-Pound Units:8.1.1.1 When the area of one surface of the sheet isdetermined, calculate the weight mass of coating as follows:C 5 W12 W2!/A# 3 K (1)where:C = weight mass of coating, oz/ft2of sheet,W1= original weight mass of specimen, g,W2= weight mass of strippe
40、d specimen, g,A = area of one surface of the sheet, in.2or mm2, and,K = a constant = 5.08 when A is in in.2, or = 3.28 3 103when A is in mm2.NOTE 3If the specimen was prepared to the dimensions as provided inNote 2, having an area of 5.08 in.2, the loss of weight mass in grams isnumerically equal to
41、 the weight mass of coating in ounces per squarefoot of sheet.8.1.1.2 When it is not possible to secure a specimen ofmeasurable area, calculate the weight mass of coating asfollows:C 5 W12 W2!/W2# 3 T 3 K (2)where:C = weight mass of coating, oz/ft2of sheet,W1= original weight mass of specimen, g,W2=
42、 weight mass of stripped specimen, g,T = thickness of stripped sheet, in. or mm, andK = a constant = 652 when T is in in., or = 25.7 when Tis in mm.8.1.2 Results in Metric Units:8.1.2.1 When the area of sheet is determined, calculate theweight mass of coating as follows:C5 W12 W2!/A# 3K (3)where:C =
43、 weight mass of coating, g/m2of sheet,W1= original weight mass of specimen, g,W2= weight mass of stripped specimen, g,A = area of one surface of the sheet, in.2or mm2, andK = a constant = 1.55 3 103when A is in in.2,or=13106when A is in mm2.NOTE 4If the specimen was prepared to the dimensions as pro
44、vided inNote 2, having an area of 3330 mm2of sheet, the factor K/A isapproximately 300, which may be used in the calculation.8.1.2.2 When it is not possible to obtain a specimen ofmeasurable area, calculate the weight mass of coating asfollows:C 5 W12 W2!/W2# 3 T 3 K (4)where:C = weight mass of coat
45、ing, g/m2of sheetW1= original weight mass of the specimen, g,W2= weight mass of the stripped specimen, g,T = thickness of stripped sheet, in. or mm, andK = a constant = 1.99 3 105when T is in in., or = 7.83 3103when T is in mm.8.2 Zinc-Coated Wire:8.2.1 Results in Inch-Pound Units:8.2.1.1 Calculate
46、the weight mass of zinc coating asfollows:C 5 W12 W2!/W2# 3 D 3 M (5)where:C = weight mass of coating, oz/ft2of stripped wiresurface,W1= original weight mass of specimen, g,W2= weight mass of stripped specimen, g,D = diameter of stripped wire, in. or mm, andM = a constant = 163 when D is in in., or
47、= 6.42 when Dis in mm.8.2.2 Results in Metric Units:8.2.2.1 Calculate the weight mass of zinc coating asfollows:C 5 W12 W2!/W2# 3 D 3 M (6)where:C = weight mass of coating, g/m2of stripped wiresurface,W1= original weight mass of specimen, g,W2= weight mass of stripped specimen, g,D = diameter of str
48、ipped wire, in. or mm, andM = a constant = 4.97 3 104when D is in in., or = 1.963 103when D is in mm.8.3 Zinc-Coated Articles Other Than Sheet or Wire:8.3.1 Results in Inch-Pound Units:8.3.1.1 Calculate the weight mass of coating as follows:C 5 W12 W2!/A# 3 N (7)where:C = weight mass of coating, oz/
49、ft2of surface,W1= original weight mass of specimen, g,W2= weight mass of stripped specimen, g,A = coated area of original specimen, in.2or mm2, andN = a constant = 5.08 when A is in in.2, or = 3.28 3 103when A is in mm2.8.3.1.2 If the specimen has a uniform thickness of basemetal, calculate the weight mass of coating as follows:C 5 W12 W2!/ W2# 3 G 3 Z (8)where:C = weight mass of coating, oz/ft2of surface,W1= ori
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