ASTM_A_90-21.pdf

This international standard was developed in accordance with internationally recgnized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.Designation:A90/A90M-21NTERNATIONALStandard Test Method forWeight Massof Coating on Iron and Steel Articles withZinc or Zinc-Alloy CoatingsThis 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 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 U.S.Department of Defense.1.Scope2.Referenced Documents1.1 This test method covers procedures for determining the2.1 ASTM Standards:2weight mass of coating on iron or steel sheet,wire,and otherA653/A653M Specification for Steel Sheet,Zinc-Coatedarticles in which the coating is zinc or a zinc alloy,such as(Galvanized)or Zinc-Iron Alloy-Coated(Galvannealed)zinc-5%aluminum(including zinc-5 aluminum-by the Hot-Dip Processmischmetal and zinc-5 aluminum-0.1 magnesium),zinc-A792/A792M Specification for Steel Sheet,55%aluminum-magnesium(including zinc-5 to 9%aluminum-Aluminum-Zinc Alloy-Coated by the Hot-Dip Processmagnesium and zinc-9 to 13 aluminum-magnesium)or 55%A875/A875M Specification for Steel Sheet,Zinc-5 Alu-aluminum-zinc.In the body of this test method,reference tominum Alloy-Coated by the Hot-Dip Processzinc coating shall be interpreted to also include zinc alloyA1046/A1046M Specification for Steel Sheet,Zinc-coating except where specifically stated otherwise.Aluminum-Magnesium Alloy-Coated by the Hot-Dip Pro-1.2 Units-The final results determined by this test methodcessshall be expressed in inch-pound units or SI units,dependingA1057/A1057M Specification for Steel,Structural Tubing,on the units used in the material specification to which theCold Formed.Welded.Carbon.Zinc-Coated(Galvanized)results are to be compared.Certain portions of the procedureby the Hot-Dip Processinvolving determination of specimen weight masshaveA1063/A1063M Specification for Steel Sheet,Twin-Rolltraditionally been performed in SI units,and correspondingCast,Zinc-Coated(Galvanized)by the Hot-Dip Processinch-pound units are not included.A1079 Specification for Steel Sheet,Complex Phase(CP),Dual Phase(DP)and Transformation Induced Plasticity1.3 For sheet products,the final results are expressed as(TRIP),Zinc-Coated(Galvanized)or Zinc-Iron Alloy.either coating weight masstotal both sides,or coating weightCoated(Galvannealed)by the Hot-Dip Processmassseparately on each side,depending on the specifiedD1193 Specification for Reagent Waterrequirements.E29 Practice for Using Significant Digits in Test Data to1.4 This standard does not purport to address all of theDetermine Conformance with Specificationssafery concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-3.Significance and Usepriate safery,health,and environmental practices and deter-3.1 This test method provides a standard method for deter-mine the applicability of regulatory limitations prior to use.mining the weight mass of zinc coatings on iron or steelFor specific hazards statements,see 5.1.products,and for evaluating conformance of such products to1.5 This international standard was developed in accor-a material specification under the jurisdiction of ASTM Com-dance with internationally recognized principles on standard-mittee A05 and its subcommittees as designated by a purchaserization established in the Decision on Principles for thein a purchase order or contract.Development of International Standards,Guides and Recom-3.1.1 This test method may be and is used by other ASTMmendations issued by the World Trade Organization TechnicalCommittees and other standards writing bodies for the purposeBarriers to Trade(TBT)Committee.of conformance testing.3.1.2 The material condition at the time of testing,samplingfrequency,specimen location and orientation,reportingThis 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.2 For referenced ASTM standards,visit the ASTM website,www.astm.org.orCurrent edition approved May 1.2021.Published May 2021.Originallycontact ASTM Customer Service at serviceastm.org.For Annual Book of A.STMapproved in 1923.Last previous edition approved in 2018 as A90/Standards volume information,refer to the standards Document Summary page onA90M-13(2018).D0L:10.1520/A0090_A0090M-21the ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM Intemational,100 Barr Harbor Drive,PO Box C700.West Conshohocken.PA 19428-2959.United StatesA90/A90M-21requirements,and other test parameters are contained in thehydrochloric acid-antimony trichloride method.Hydrochloricpertinent material specification or in a general requirementacid fumes are present,and hydrogen gas is evolved in thespecification for the particular product form.stripping process.Therefore,the test should be performed3.1.3 A coating of zinc on iron or steel articles providesunder conditions of adequate ventilation.A fume hood isprotection against corrosion.As the protection is provided byrecommended for large numbers of samples or where the test issacrificial loss of zinc,the degree of protection is proportionalto be carried out frequently over extended periods of time.to the weight massof zinc coating.Specifications for zinc-5.2 Warning-Mixing of sulfuric acid with water couldcoated articles frequently provide for different designations orresult in severe injuries if not properly done.Mixing must beclasses of coating so that the purchaser can select the coatingdone by slowly adding sulfuric acid to water due to the heatweight massmost suitable for the intended application.generated and possible splashing.Under no circumstances3.2 This test method determines the average coating weightshould the water be added to the acid.The mixing should bemassover a specified area,from which the average thicknessperformed under an acid fume hood.can be calculated.Other test methods not described herein candetermine the thickness directly at point locations on the6.Samplingcoating:in such cases,the required test method is described in6.1 Zinc-Coated Sheets-Samples for weight massofthat material specification or by reference to another appropri-coating determination shall be secured in accordance withate test method standard.Specifications A653/A653M,A792/A792M,A875/A875M,A1046/A1046M.A1057/A1057M.A1063/A1063M.orA10794.Reagentsdepending on the type of coating.4.1 Purity of Reagents-Reagent grade chemicals shall beNorE 2-For convenience in calculating test results in inch-poundused in all tests.Unless otherwise indicated,it is intended thatunits,the specimen should have an area of 5.08 in.of sheet(2.25all reagents shall conform to the specifications of the Commit-0.01 in.square or 2.540.01 in.in diameter).The weight massoftee on Analytical Reagents of the American Chemical Society,coating in grams on a specimen of that area is numerically equal to thewhere such specifications are available.3 Other grades may beweight massof coating in ounces per square foot of sheet.For results tobe reported in metric units,the specimen should have an area of 3330 mm2used,provided it is first ascertained that the reagent is ofof sheet(57.7 0.1 mm square or 65.1 0.1 mm in diameter).sufficiently high purity to permit its use without lessening the6.2 Zinc-Coated Wire-Samples shall be secured as desig-accuracy of the determination.nated in the appropriate specification.The specimen of wire4.2 Purity of Water-Water used to prepare chemical solu-may be of any length over 12 in.305 mm,but preferablytions shall be reagent water as defined by Type Iv ofabout 24 in.609 mm.Where a continuous length is notSpecification D1193.available,shorter lengths totaling over 12 in.300 mm,but4.3 Antimony Trichloride Solution-Dissolve 20 g of Sb2O3preferably about 24 in.600 mm,shall be used.Since theor 32 g of SbCl3 in 1000 mL of HCI(sp gr 1.18 to 1.19).density of the steel is known 0.283 Ib/in.3 7830 kg/m,it isnot necessary to use a specific length of specimen.4.4 Hydrochloric Acid(sp gr 1.18 to 1.19)-Concentratedhydrochloric acid(HCl).6.3 Zinc-Coated Articles Other Than Sheet or Wire-Samples for weight massof coating determination shall be4.5 Hydrochloric Acid-Antimony Trichloride Solution-secured as designated in the appropriate specification.ExceptAdd 5 mL of antimony trichloride solution to 100 mL of HCIas otherwise provided,the specimens should have a minimum(spgr1.18to1.19)area of 3 in.2000 mm2of zinc-coated surface.For very4.6 Hydrochloric Acid(1+1)-Mix 500 mL of HCI(sp grsmall items,several pieces may have to be stripped to obtain1.18 to 1.19)with 500 mL of reagent water and cool to roomthe minimum area.temperature6.3.1 In the case of threaded articles,such as bolts and4.7 Sulfuric Acid(25 75)-Mix 250 mL of H2SO(sp grscrews,the determination shall be made on a portion of the1.84)with 750 mL of reagent water and cool to roomarticles that does not include any thread.temperature.7.ProcedureNorE 1-It is advisable to use an inhibitor with acid solution(for7.1 Strip the zinc coating from the specimens by using oneexample,Hexamethylamine Tetramine or similar)at the concentrationof the following methods:hydrochloric acid(1 1),hydro-level according to the manufacturers recommendations to prevent attackof the substrate.chloric acid-antimony trichloride solution,or sulfuric acid(25+75).For zinc alloy coatings containing less than 90 zinc,5.Hazardsthe stripping shall be done using hydrochloric acid(1+1)orsulfuric acid(25 75).5.1 Warning-Small amounts of the poisonous gas stibine(SbH3)may be evolved during the stripping process using the7.2 Clean the specimens by washing with solvent naphtha orother suitable solvent,then rinse with alcohol,and dry thor-oughly.3Reagent Chemicals.American Chemical Society Specifications,Am.Chemi-cal Soc.Washington.DC.For suggestions on the testing of reagents not listed by7.3 Determine the weight massof the specimens individu-the American Chemical Society,see Analar Standards for Laboratory U.K.ally to the nearest 0.01 g,except for articles other than sheet orChemicals,BDH Ltd.,Poole,Dorset.and theUnited States Pharmacopeia.wire with a specimen weight massgreater than 125 g,A90/A90M-21requirements,and other test parameters are contained in thehydrochloric acid-antimony trichloride method.Hydrochloricpertinent material specification or in a general requirementacid fumes are present,and hydrogen gas is evolved in thespecification for the particular product form.stripping process.Therefore,the test should be performed3.1.3 A coating of zinc on iron or steel articles providesunder conditions of adequate ventilation.A fume hood isprotection against corrosion.As the protection is provided byrecommended for large numbers of samples or where the test issacrificial loss of zinc,the degree of protection is proportionalto be carried out frequently over extended periods of time.to the weight massof zinc coating.Specifications for zinc-5.2 Warning-Mixing of sulfuric acid with water couldcoated articles frequently provide for different designations orresult in severe injuries if not properly done.Mixing must beclasses of coating so that the purchaser can select the coatingdone by slowly adding sulfuric acid to water due to the heatweight massmost suitable for the intended application.generated and possible splashing.Under no circumstances3.2 This test method determines the average coating weightshould the water be added to the acid.The mixing should bemassover a specified area,from which the average thicknessperformed under an acid fume hood.can be calculated.Other test methods not described herein candetermine the thickness directly at point locations on the6.Samplingcoating:in such cases,the required test method is described in6.1 Zinc-Coated Sheets-Samples for weight massofthat material specification or by reference to another appropri-coating determination shall be secured in accordance withate test method standard.Specifications A653/A653M,A792/A792M,A875/A875M,A1046/A1046M.A1057/A1057M.A1063/A1063M.orA10794.Reagentsdepending on the type of coating.4.1 Purity of Reagents-Reagent grade chemicals shall beNorE 2-For convenience in calculating test results in inch-poundused in all tests.Unless otherwise indicated,it is intended thatunits,the specimen should have an area of 5.08 in.of sheet(2.25all reagents shall conform to the specifications of the Commit-0.01 in.square or 2.540.01 in.in diameter).The weight massoftee on Analytical Reagents of the American Chemical Society,coating in grams on a specimen of that area is numerically equal to thewhere such specifications are available.3 Other grades may beweight massof coating in ounces per square foot of sheet.For results tobe reported in metric units,the specimen should have an area of 3330 mm2used,provided it is first ascertained that the reagent is ofof sheet(57.7 0.1 mm square or 65.1 0.1 mm in diameter).sufficiently high purity to permit its use without lessening the6.2 Zinc-Coated Wire-Samples shall be secured as desig-accuracy of the determination.nated in the appropriate specification.The specimen of wire4.2 Purity of Water-Water used to prepare chemical solu-may be of any length over 12 in.305 mm,but preferablytions shall be reagent water as defined by Type Iv ofabout 24 in.609 mm.Where a continuous length is notSpecification D1193.available,shorter lengths totaling over 12 in.300 mm,but4.3 Antimony Trichloride Solution-Dissolve 20 g of Sb2O3preferably about 24 in.600 mm,shall be used.Since theor 32 g of SbCl3 in 1000 mL of HCI(sp gr 1.18 to 1.19).density of the steel is known 0.283 Ib/in.3 7830 kg/m,it isnot necessary to use a specific length of specimen.4.4 Hydrochloric Acid(sp gr 1.18 to 1.19)-Concentratedhydrochloric acid(HCl).6.3 Zinc-Coated Articles Other Than Sheet or Wire-Samples for weight massof coating determination shall be4.5 Hydrochloric Acid-Antimony Trichloride Solution-secured as designated in the appropriate specification.ExceptAdd 5 mL of antimony trichloride solution to 100 mL of HCIas otherwise provided,the specimens should have a minimum(spgr1.18to1.19)area of 3 in.2000 mm2of zinc-coated surface.For very4.6 Hydrochloric Acid(1+1)-Mix 500 mL of HCI(sp grsmall items,several pieces may have to be stripped to obtain1.18 to 1.19)with 500 mL of reagent water and cool to roomthe minimum area.temperature6.3.1 In the case of threaded articles,such as bolts and4.7 Sulfuric Acid(25 75)-Mix 250 mL of H2SO(sp grscrews,the determination shall be made on a portion of the1.84)with 750 mL of reagent water and cool to roomarticles that does not include any thread.temperature.7.ProcedureNorE 1-It is advisable to use an inhibitor with acid solution(for7.1 Strip the zinc coating from the specimens by using oneexample,Hexamethylamine Tetramine or similar)at the concentrationof the following methods:hydrochloric acid(1 1),hydro-level according to the manufacturers recommendations to prevent attackof the substrate.chloric acid-antimony trichloride solution,or sulfuric acid(25+75).For zinc alloy coatings containing less than 90 zinc,5.Hazardsthe stripping shall be done using hydrochloric acid(1+1)orsulfuric acid(25 75).5.1 Warning-Small amounts of the poisonous gas stibine(SbH3)may be evolved during the stripping process using the7.2 Clean the specimens by washing with solvent naphtha orother suitable solvent,then rinse with alcohol,and dry thor-oughly.3Reagent Chemicals.American Chemical Society Specifications,Am.Chemi-cal Soc.Washington.DC.For suggestions on the testing of reagents not listed by7.3 Determine the weight massof the specimens individu-the American Chemical Society,see Analar Standards for Laboratory U.K.ally to the nearest 0.01 g,except for articles other than sheet orChemicals,BDH Ltd.,Poole,Dorset.and theUnited States Pharmacopeia.wire with a specimen weight massgreater than 125 g,A90/A90M-218.2.2 Results in Metric Units:where:8.2.2.1 Calculate the weight massof zinc coating as=weight massof coating,g/m2 of surface,follows:Woriginal weight massof specimen,g,C=(W,-W2)/WDM(6)W2=weight massof stripped specimen,g,Gthickness of stripped specimen,in.or mm,andwhere:Z=a constant=9.95l03 when G is in in,or=3.92weight massof coating,g/m2 of stripped wire103 when G is in mm.surface.W,original weight massof specimen,g.9.ReportW,weight massof stripped specimen,g,9.1 Weight massof coating on zinc-coated sheet is ex-Ddiameter of stripped wire,in.or mm,andpressed in weight massper unit area of sheet,and is either theM=a constant=4.9710when D is in in.,or=1.96sum of the weights massesof coating on both sides of the103 when D is in mm.sheet,or single side weight masson each of the two sides.8.3 Zinc-Coated Articles Other Than Sheet or Wire:Weights massesof coating on each side of the sheet are not8.3.1 Results in Inch-Pound Units:necessarily equal,even when both sides are exposed to the8.3.1.1 Calculate the weight massof coating as follows:molten metal or plating solution simultaneously.Coatingweights masseson all zinc-coated articles other than sheetsC=(W-W2)/A XN(7)are expressed in weight massper unit area of surface.where:9.2 Report the weight massof zinc coating to the nearestCweight massof coating,oz/ft2 of surface,0.01 oz/ft2 when reporting in inch-pound units.original weight massof specimen,g,W2weight massof stripped specimen,g.9.3 Report the weight massof zinc coating to the nearestAcoated area of original specimen,in.or mm2,and1 g/m2 when reporting in metric units.Na constant 5.08 when A is in in.2,or 3.28 x 1039.4 When the weight massof coating of a number ofwhen A is in mm-.specimens is to be averaged to determine conformance with a8.3.1.2 If the specimen has a uniform thickness of basespecification limit,the average value shall be reported to themetal,calculate the weight massof coating as follows:precision described in 9.2 and 9.3 in accordance with theC=(W,-W)/W2GZ(8)Rounding Method of Practice E29.10.Precision and Biaswhere:Cweight massof coating,oz/ft2 of surface,10.1 The precision of this test method is based on anW,=original weight massof specimen,g,interlaboratory study conducted in 2006.Each of ten laborato-W2weight massof stripped specimen,g,ries tested three replicates of two different materials.*Data wasGthickness of stripped specimen,in.or mm,andrecorded in inch-pound units only and should not be consideredZa constant 326 when G is inin.,or 12.8 when G ismetric equivalents.See Table I for a statistical summary of thein mm.test results.8.3.2 Results in Metric Units:10.1.1 Repeatability-Two test results obtained within one8.3.2.1 Calculate the weight massof zinc coating aslaboratory shall be judged not equivalent if they differ by morefollows:than the“r”value for that material;“r”is the intervalrepresenting the critical difference between two test results forC=(W-W)/A XN(9)the same material,obtained by the same operator using thewhere:same equipment on the same day in the same laboratory.Cweight massof coating,g/m2 of surface,10.1.2 Reproducibility-Two test results shall be judged notoriginal weight massof specimen,g.equivalent if they differ by more than the Rvalue for thatW2weight massof stripped specimen,g,material;Ris the interval representing the difference be-Acoated area of original specimen,in.2 or mm2,andtween two test results for the same material,obtained byNa constant 1.55 x 10 when A is inin.2,or=1 x 106different operators using different equipment in different labo-when A is in mm-.ratories.8.3.2.2 If the specimen has a uniform thickness of basemetal,calculate the weight massof coating as follows:Supporting data have been filed at ASTM Interational Headquarters and maybe obtained by requesting Research Report RR:A05-1003.Contact ASTM CustomerC=(w,-W2)/wGZ(10)Service at serviceastm.org.TABLE 1 Weight Mass Coating(in oz.ft2)NorE 1-S means the standard deviation of r(repeatability).S&means the standard deviation for R(reproducibility)MaterialSHot Dipped Zinc-Coated Samples1.1007800.0218950.0153330.0252220.0429330.070621Electrolytic Zinc-Coated Samples0.4032210.0087900.0083780.0111380.0234570.0311874A90/A90M-2110.1.3 Any judgment in accordance with these two state-11.Keywordsments would have an approximate 95 probability of being11.1 55 aluminum-zinc alloy coating;coating weightcorrect.mass;steel sheet;steel wire;zinc alloy coatings;zinc coating;10.2 Bias-At the time of the study,there was no acceptedzinc-5 aluminum alloy coating:zinc-5 aluminum-0.1reference material suitable for determining the bias for this testmagnesium alloy coating;zinc-5%aluminum-mischmetal al-method.therefore no statement on bias is being made.loy coating;zinc-5 to 9 aluminum-magnesium alloy coating:10.3 The precision statement was determined through sta-zinc-9 to 13 aluminum-magnesium alloy coatingtistical examination of three results,from ten laboratories.ontwo materials.SUMMARY OF CHANGESCommittee A05 has identified the location of selected changes to this standard since the last issue(A90/A90M-13(2018)that may impact the use of this standard.(May 1,2021.)(1)Revised Section 3(Significance and Use)to comply with(2)Editorial corrections were made throughout.the requirements of Form and Style,Section A9(Test Meth-ods).ASTM Intemational takes no position respecting the validity of any patent rights 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 any 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 will 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 ASTM 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 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