1、Designation: A 90/A 90M 09Standard Test Method forWeight Mass of Coating on Iron and Steel Articles withZinc or Zinc-Alloy Coatings1This standard is issued under the fixed designation A 90/A 90M; the number immediately following the designation indicates the yearof original adoption or, in the case
2、of revision, 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 m
3、ethod 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) or55 % aluminum-zinc. In the body of
4、 this test method, referenceto zinc coating shall be interpreted to also include zinc alloycoating except where specifically stated otherwise.1.2 The final results determined by this test method shall beexpressed in inch-pound units or SI units, depending on theunits used in the material specificati
5、on 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-poundunits are not included.1.3 For sheet products, the final results are expressed aseither coating weight
6、 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, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safet
7、y 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:2A 653/A 653M Specification for Steel Sheet, Zinc-Coated(Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed)by the Hot-Dip
8、 ProcessA 792/A 792M Specification for Steel Sheet, 55 %Aluminum-Zinc Alloy-Coated by the Hot-Dip ProcessA 875/A 875M Specification for Steel Sheet, Zinc-5 %Aluminum Alloy-Coated by the Hot-Dip ProcessD 1193 Specification for Reagent WaterE29 Practice for Using Significant Digits in Test Data toDete
9、rmine 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 protectionis
10、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. Reagents
11、4.1 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 grades may
12、 beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.4.2 Purity of WaterWater used to prepare chemical solu-tions shall be reagent water as defined by Type IV ofSpecification D 1193.4.3 Antimony
13、Trichloride Solution Dissolve 20 g ofSb2O3or 32 g of SbCl3in 1000 mL of HCl (sp gr 1.18 to 1.19).4.4 Hydrochloric 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.
14、19).1This test method is under the jurisdiction of ASTM Committee A05 onMetallic-Coated Iron and Steel Products and is the direct responsibility ofSubcommittee A05.07 on Methods of Testing.Current edition approved May 1, 2009. Published June 2009. Originallyapproved in 1923. Last previous edition ap
15、proved in 2007 as A 90/A 90M - 07.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3“Reagent Chemicals, Americ
16、an Chemical Society Specifications,” Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing of 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 se
17、ction appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 to roomtemperature.4.7 Sulfuric Acid (2
18、5 + 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 manufacturers recommendations to prevent attackof
19、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 thestripping process. Therefore, the test should
20、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 injuries if not properly done. Mixing must b
21、edone 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 weight mass ofcoating determination shall be
22、secured in accordance withSpecifications A 653/A 653M, A 792/A 792M,orA 875/A 875M depending on the type of coating.NOTE 2For convenience in calculating test results in inch-poundunits, the specimen should have an area of 5.08 in.2of sheet (2.25 60.01-in. square or 2.54 6 0.01 in. in diameter). The
23、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 (57.7 6 0.1-mm square or 65.1 6 0.1 mm in diameter).6.2 Zinc
24、-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 totaling over 12 in. 300 mm, butpreferably about 24 in. 600
25、 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 shall besecured as designated in the appropriate specification
26、. 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, such as bolts andscrews, the determination shall be made on
27、 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 sulfuric acid (25+ 75). For zinc alloy coatings containing less t
28、han 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 the weight mass of the specimens individu-ally to the neare
29、st 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 solution and allow to remain until the violentevolution of hyd
30、rogen 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 stripping becomes inconveniently long. The tem-perature of th
31、e 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 in the initial determination.7.4 Sheet SpecimensWhen measur
32、ing 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, they shall be presumedto have an area of 5.08 in.23330 mm2. W
33、hen 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 oneside of sheet material, use the procedure described in 7.3,exc
34、ept 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-off” to the specimen after the initial determination ofweigh
35、t 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 the coating weight mass on the second sidesubsequently withou
36、t a “stop-off” on the first side.7.5 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 or Wire Determine thetotal coated area of the original specimen to the
37、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.A 90/A 90M 0928. Calculation8.1 Zinc-Coated Sheet:8.1.1 Results in Inch-Pound Units:8.1.1.1
38、 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 stripped specimen, g,A = area of one surface of the sheet, in.2or
39、 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 the weight mass of coating in ounces per squarefoot of sh
40、eet.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= weight mass of stripped specimen, g,T = thickness of stri
41、pped 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 = weight mass of coating, g/m2of sheet,W1= original weight
42、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 provided inNote 2, having an area of 3330 mm2of sheet, the fa
43、ctor 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 coating, g/m2of sheetW1= original weight mass of the specimen,
44、 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 the weight mass of zinc coating asfollows:C 5 W12 W2!/W2#
45、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 = 6.42 when Dis in mm.8.2.2 Results in Metric Units:8.2.2.
46、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 stripped wire, in. or mm, andM = a constant = 4.97 3 104when
47、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/ft2of surface,W1= original weight mass of specimen, g,W2=
48、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)
49、where:C = weight mass of coating, oz/ft2of surface,W1= original weight mass of specimen, g,W2= weight mass of stripped specimen, g,G = thickness of stripped specimen, in. or mm, andZ = a constant = 326 when G is in in., or 12.8 when G isin mm.8.3.2 Results in Metric Units:8.3.2.1 Calculate the weight mass of zinc coating asfollows:C 5 W12 W2!/A# 3N (9)where:C = weight mass of coating, g/m2of surface,W1=
