ASTM_B_893_-_98_2013.pdf

Designation:B89398(Reapproved 2013)Standard Specification forHard-Coat Anodizing of Magnesium for EngineeringApplications1This standard is issued under the fixed designation B893;the number immediately following the designation indicates the 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 specification covers requirements for electrolyti-cally formed oxide coatings on magnesium and magnesiumalloy parts where appearance,abrasion resistance,and protec-tion against corrosion are important.1.2 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 safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray(Fog)ApparatusB244 Test Method for Measurement of Thickness of AnodicCoatings on Aluminum and of Other NonconductiveCoatings on Nonmagnetic Basis Metals with Eddy-Current InstrumentsB322 Guide for Cleaning Metals Prior to ElectroplatingB374 Terminology Relating to ElectroplatingB487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination ofCross SectionB537 Practice for Rating of Electroplated Panels Subjectedto Atmospheric ExposureB602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB762 Test Method of Variables Sampling of Metallic andInorganic CoatingsD3951 Practice for Commercial PackagingD4060 Test Method for Abrasion Resistance of OrganicCoatings by the Taber Abraser3.Terminology3.1 Definitions:3.1.1 DefinitionsFor definitions of terms relating to thisspecification see Terminology B374.3.1.2 anodizingan electrolytic oxidation process in whichthe surface of a metal,when anodic,is converted to a coatinghaving desirable protective or functional properties.3.1.3 hard coatin anodizing magnesium,an anodic oxidecoating on magnesium with a higher apparent density andthickness,and a greater resistance to wear than the base metal.4.Classification4.1 Coating DesignationThickness.4.1.1 Minimum thickness of 20 m.4.2 TYPEPost treatments.4.2.1 TYPE ANo post treatment.4.2.2 TYPE BPurchaser specified.5.Ordering Information(to be supplied by the purchaserto the producer.)5.1 Alloy DesignationWhen ordering articles anodized inaccordance with this specification,the purchaser shall state,thealloy designation number.5.2 AppearanceUnlessotherwisespecifiedbythepurchaser,an off-white color shall be acceptable for TYPE Acoating.The purchaser shall specify the color and surfaceappearance required for TYPE B coatings.All coatings shall beuniform in color and free from stains.Alternatively,samplesshowing the required finish,or range of finishes,shall besupplied or approved by the purchaser.When required,thebasis material may be subjected to such mechanical polishingas may be required to yield the desired final surface character-istics.5.3 Significant SurfaceThe areas of the article covered bythe coating,for which the coating is essential for service orappearance or both.5.3.1 Contact MarksContact marks will occur.The pur-chaser shall specify where contact marks are unacceptable.1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.07 on Conversion Coatings.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 1998.Last previous edition approved in 2008 as B893 98(2008).DOI:10.1520/B0893-98R13.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.4 TolerancesDimensional build-up is approximatelyone-half of anodic film thickness.The order document shallinclude any coating thickness tolerances and shall not exceedany applicable drawing dimensions.5.5 The purchaser shall provide the number for this standardTYPE.5.6 The purchaser shall state any special post treatments(see 4.2 and 5.2).5.7 Test MethodsThe purchaser shall state the test meth-od(s)by which the coated article will be evaluated(see Section8).5.8 Sampling Plansee Section 9.5.9 Any requirement for certification(see Section 11).5.10 Any requirement for packaging(see Section 12).6.Materials and Process6.1 Process:6.1.1 Basis MetalThis specification does not specify re-quirements for the surface condition of the basis metal beforeanodizing,but agreement should preferably be rea