1、Designation: B 893 98 (Reapproved 2008)Standard Specification forHard-Coat Anodizing of Magnesium for EngineeringApplications1This standard is issued under the fixed designation B 893; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 mag
3、nesiumalloy 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
4、 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) ApparatusB 244 Test Method for Measurement of Thickness of An-odic Coatings on Aluminum and of Other NonconductiveCoatings
5、 on Nonmagnetic Basis Metals with Eddy-CurrentInstrumentsB 322 Guide for Cleaning Metals Prior to ElectroplatingB 374 Terminology Relating to ElectroplatingB 487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination of CrossSectionB 537 Practice for Rating of E
6、lectroplated Panels Subjectedto Atmospheric ExposureB 602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB 697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB 762 Test Method of Variables Sampling of Metallic andInorganic
7、CoatingsD 3951 Practice for Commercial PackagingD 4060 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 B 374.3.1.2 anodizingan electrolytic oxidation proce
8、ss 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
9、. 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 inaccor
10、dance with this specification, the purchaser shall state, thealloy designation number.5.2 AppearanceUnless otherwise specified by the pur-chaser, an off-white color shall be acceptable for TYPE Acoating. The purchaser shall specify the color and surfaceappearance required for TYPE B coatings.All coa
11、tings 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 sur
12、face character-istics.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 April 1, 2008. Published April 2008. Originallyapproved in 1998. Last pre
13、vious edition approved in 2003 as B 89398(2003).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.1Copyright AS
14、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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
15、 shall specify where contact marks are unacceptable.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
16、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 Sectio
17、n 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 reached be-tween the purchaser and the pro
18、ducer that the surface conditionof the basis metal is satisfactory.6.1.2 Surface PreparationPreparatory procedures andcleaning of the basis material may be necessary, see PracticeB 322.6.1.3 Hard-CoatingFollowing the preparatory operations,the articles are introduced into the solution for a period o
19、f timeat the current density and temperature required to produce thehard-coated surface.NOTE 1Hard-coating solutions and operating conditions are commer-cially available. The appropriate operating instructions should be fol-lowed.NOTE 2Intricately shaped articles may not receive the same thicknessof
20、 coating in recessed areas due to lower current densities. Auxiliarycathodes, may be used to improve anodize thickness in these areas.6.2 Post Treatments:6.2.1 Final RinsingRinsing subsequent to anodizing isnecessary to remove all traces of the electrolyte that may affectthe appearance and performan
21、ce of the part. Deionized ordistilled water may be used to avoid water spots.6.2.2 Post TreatmentSurface sealers or topcoats may bespecified to reduce friction, add color, or further increaseperformance.7. Requirements7.1 Acceptance:7.1.1 Visual DefectsThe significant surfaces of the articleto be ha
22、rdcoated shall be free of clearly visible defects such aspits, roughness, striations, or discoloration when examinedwith normal or corrected to 20/20 eyesight at a distance ofapproximately 0.5 m.NOTE 3Defects in the surface of the basis material such as scratches,porosity, inclusions, etc., may adve
23、rsely affect the appearance andperformance of the article.7.1.2 Thickness:7.1.2.1 Coating Thickness for SC20The anodic film thick-ness shall be a minimum of 20 m and not exceed 30 m on thesignificant surface.7.1.2.2 TestHard-coating thickness shall be evaluated byone or more of the following test me
24、thods in Section 8.7.2 Qualification TestsThe process shall be evaluatedmonthly or more frequently if required by the purchaser usingthe following test methods on panels that are of the same alloyof the parts coated with TYPE A hard coat.7.2.1 Corrosion TestUse method described in 8.17.2.2 Abrasion
25、Resistance TestUse the Taber Abraser testmethod in Annex A1 of this specification.8. Test Methods8.1 Corrosion TestPanel(s) shall be subjected to a 5 % saltspray (fog) test in accordance with Practice B117for 336 h.The panel(s) shall be prepared and evaluated in accordancewith Practice B 537. A prot
26、ective rating of 6 or less isconsidered a failure.8.2 Abrasion Resistance TestTest panels in accordancewith Annex A1. The acceptance criteria shall be as follows.8.2.1 Abrasive Wheel No. CS-10A wear index of morethan 7 mg/1000 cycles or less than 10 000 wear cycles shall beconsidered a failure.8.2.2
27、 Abrasive Wheel No. CS-17A wear index of morethan 20 mg/1000 cycles or less than 5 000 wear cycles shall beconsidered a failure.8.3 Thickness Tests:8.3.1 Eddy-Current Method (Test Method B 244)8.3.2 Microscopical Cross Section Method (Test MethodB 487).9. Sampling9.1 The purchaser and producer are u
28、rged to employ statis-tical process control in the coating process. Properly per-formed, statistical process control will ensure coated productsof satisfactory quality and will reduce the amount of accep-tance inspection. The sampling plan used for the inspection ofthe quality coated article shall b
29、e agreed upon between thepurchaser and producer.9.1.1 When a collection of coated articles (inspection lot,see 8.2) is examined for compliance with the requirementsplaced on the articles, a relatively small number of the articles(sample) is selected at random and is inspected. The inspectionlot is t
30、hen classified as complying with the requirements basedon the results of the inspection of the sample. The size of thesample and the criteria for compliance are determined by theapplication of statistics. The procedure is known as samplinginspection. Test Method B 602, Guide B 697, and Test MethodB
31、762 contain sampling plans that are designed for samplinginspection of coatings.9.1.2 Test Method B 602 contains four sampling plans, threefor use with tests that are non-destructive and one when theyare destructive. Test Method B 602 provides a default plan ifone is not specified.B 893 98 (2008)29.
32、1.3 Guide B 697 provides a large number of plans andalso gives guidance in the selection of a plan. Guide B 697provides a default plan if one is not specified.9.1.4 Test Method B 762 can be used only for coatingrequirements that have a numerical limit, such as coatingthickness. The test must yield a
33、 numeric value and certainstatistical requirements must be met. Test Method B 762contains several plans and also gives instructions for calculat-ing plans to meet special needs. Test Method B 762 provides adefault plan if one is not specified.9.2 An inspection lot shall be defined as a collection of
34、coated articles that are the same kind. That have been producedto the same specification, that have been coated by a singlesupplier at one time or approximately the same time, underessentially identical conditions, and that are submitted foracceptance or rejection as a group.10. Rejection and Hearin
35、g10.1 Parts that fail to conform to the requirements of thisspecification may be rejected. Rejection should be reported tothe producer or supplier promptly, and in writing. In case ofdissatisfaction with test results, the producer or supplier maymake a claim for a rehearing.11. Certification11.1 Whe
36、n specified in the purchase order or contract, thepurchaser shall be furnished certification that samples repre-senting each lot have been tested or inspected as directed in thisspecification and that the requirements have been met. Whenspecified in the purchase order or contract, a report of the te
37、stresults shall be furnished.12. Packaging12.1 If packaging requirements are necessary under thisspecification, they shall be in accordance with Practice D 3951.13. Keywords13.1 anodizing; hard coat; magnesiumANNEX(Mandatory Information)A1. TABER ABRASER WEAR TEST METHODA1.1 ScopeA1.1.1 This test me
38、thod will evaluate the resistance of thecoating to abrasive wear. The test is performed by coating aspecial specimen with the coating of interest, mechanicallyrotating the panel under an abrasive wheel and measuring theloss of material. The test is generally performed to 5000 cycleswith CS-17 or 10
39、000 cycles with a CS-10 but can be extendedto as high as 25 000 cycles.NOTE A1.1Variations in the results of this test method have beenattributed to humidity in the laboratory and storage conditions of thewheels. Care should be taken to control the humidity of the wheelsbetween tests.A1.1.2 The resu
40、lts are variable between tests and thereforethree (3) coated test specimens should be tested for 5000 or10 000 cycles each depending on the type of abrasive wheel.The results should be averaged and the abrasion wear reportedas the weight loss in mg/1000 cycles (Taber Wear Index).NOTE A1.2The outer s
41、urface of the coating may contain roughness orin the case of anodizing may be less dense which will cause a greater lossin the first 1000 cycles than the remaining cycles. By not reporting the first1000 cycles a more representative value for the bulk coating is obtained.For these applications, howev
42、er the outer density and wear debris in thefirst 1000 cycles is important.A1.2 ApparatusA1.2.1 Taber Abraser Wear Testing UnitThis unit must becapable of applying a 1000 g load on the wheel and have anoperating vacuum for removal of wear debris while in test.A1.2.2 Abrasion WheelsUse the CS10 or CS1
43、7 (ResilientRubber) Taber Wheels. To resurface the wheels use the CS11discs from Taber.NOTE A1.3The hardness of the wheels can change with time and caneffect the reproducibility of the results. (see Test Method D 4060)Redressing the wheels as well as using new wheels and controlling thehumidity will
44、 improve the reproducibility. Round Robin tests betweenlaboratories has produced a bias of 50 % with these factors in controlwhile the intra laboratory bias is 20 %.A1.2.3 SpecimensTest specimens shall be made frommagnesium plate 4 by 4 by 0.250 in. min (100 by 100 by 2 mmto 6.35 mm) with a 0.250 in
45、. (6.35 mm) hole in the center.A1.2.4 Analytical BalanceScale shall be capable of mea-suring to 150 g 6 0.1 mg.A1.3 ProcedureA1.3.1 Coat SpecimensCoat a set of three (3) specimensto the thickness of 20 to 30 m.A1.3.2 Testing SpecimensPerform the following test oneach of the three specimens.A1.3.2.1
46、Step 1Weigh SpecimensCool the specimen toambient temperature and weigh to the nearest 0.1 mg.A1.3.2.2 Step 2Dress WheelThe wheel shall be dressedusing a CS11 disc for 50 cycles.A1.3.2.3 Step 3, Wear Specimens, 5000 cycles for CS-17 or10 000 cycles for a CS-10. Test the specimens by loading thewheel
47、to 1000 g and wearing the specimen for the requiredcycles.A1.3.2.4 Step 4, Weigh SpecimenCool the specimen toambient temperature and weigh to the nearest 0.1 mg.B 893 98 (2008)3ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item ment
48、ionedin 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
49、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 c
