ASTM B480-1988(2010) Standard Guide for Preparation of Magnesium and Magnesium Alloys for Electroplating《电镀用镁和镁合金制备的标准指南》.pdf

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1、Designation: B480 88 (Reapproved 2010)Standard Guide forPreparation of Magnesium and Magnesium Alloys forElectroplating1This standard is issued under the fixed designation B480; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y

2、ear 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 guide describes two processes used for plating onmagnesium and magnesium alloys: direct electroless nickel

3、plating and zinc immersion. Some users report that the directelectroless nickel procedure does not produce quite as high alevel of adhesion as zinc immersion.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard

4、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. For specific hazardstatements, s

5、ee 5.1.1 and 5.2.9.2.2. Referenced Documents2.1 ASTM Standards:2B322 Guide for Cleaning Metals Prior to Electroplating3. Significance and Use3.1 Metals are electroplated on magnesium for variouspurposes: solderability, RF grounding, hermetic sealing, wearresistance, corrosion resistance, appearance,

6、 and electricalconductivity, for example. Because magnesium is covered witha naturally occurring oxide film, usual procedures for thepreparation of metals for autocatalytic or electrolytic platingcannot be used.4. Reagents4.1 Purity of ReagentsAll acids and chemicals used inthis guide are of technic

7、al grade. Acid and base solutions arebased on the following assay materials:Ammonium hydroxide (NH4OH) 30 mass %, density 0.895 g/LNitric acid (HNO3) 67 mass %, density 1.16 g/LSulfuric acid (H2SO4) 93 mass %, density 1.40 g/LHydrofluoric acid (HF) 70 mass %, density 1.258 g/LPhosphoric acid (H3PO4)

8、 85 mass %, density 1.689 g/L4.2 Purity of WaterAll water used for solutions, whethernew or recycled, should be monitored for cations, anions, andorganic matter that are known to interfere with the platingprocess.5. Processes5.1 Procedures:5.1.1 Wheel polish and buff parts for smooth, highly pol-ish

9、ed surfaces. Tumble and burnish small parts.Acid pickle theparts after use of wire brushing or steel wool. (WarningBecause of the high flammability of powdered magnesium,special precautions against fire are important. Polishing andbuffing lathes should be kept scrupulously clean. Dust fromgrinding i

10、n and around lathes should be swept up and placed inclosed containers for proper disposal. Exhaust systems shouldbe cleaned frequently and the residues handled similarly. Ifabrasives are used in tumble finishing, similar precautionarytechniques should be used for the solids from the abrasiveslurry.)

11、5.1.2 ChemicalRemove oil and grease in an alkaline soakcleaner. Remove other soils and coatings in suitable acidpickling solutions.NOTE 1General information on the cleaning of metals is given inPractice B322.5.2 General Electroplating Procedure:5.2.1 Remove oil, grease, and other soils left from pre

12、plat-ing procedures by soak cleaning in an alkaline cleaner suitablefor magnesium.5.2.2 Rinse in cold water.NOTE 2As generally used in rinsing terminology, cold water refers towater from an unheated water supply as opposed to heated water used fordrying or other purposes. In some areas, particularly

13、 in water, ambientwater temperatures may be too low for effective rinsing. In thoseinstances, the rinse water may need to be heated. A minimum temperatureof 16C is recommended for effective rinsing.1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is t

14、he direct responsibility of Subcommittee B08.02 on PreTreatment.Current edition approved Nov. 1, 2010. Published November 2010. Originallyapproved in 1968. Last previous edition approved in 2006 as B480 88 (2006).DOI: 10.1520/B0480-88R10.2For referenced ASTM standards, visit the ASTM website, www.as

15、tm.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 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2.3 El

16、ectroclean parts in an alkaline electrocleaner suit-able for magnesium. Make the magnesium cathodic at 7.5 to 13A/dm2and 85C.5.2.4 Rinse in cold water.5.2.5 Pickle in one of the following solutions:5.2.5.1 Ferric Nitrate Pickle:3Chromic acid (CrO3) 180 g/LFerric nitrate (Fe(NO3)9H2O) 40 g/LPotassium

17、 fluoride (KF) 3.5 g/LTemperature 16 to 38CTime 15sto3minNOTE 3This pickle removes metal from a surface at the rate of 3m/min at 38C. Where no dimensional change can be tolerated, use of thechromic acid pickle in 5.2.5.2 is recommended.5.2.5.2 Chromic Acid Pickle:3Chromic acid (CrO3) 180 g/LTemperat

18、ure 16 to 93CTime 2to10minNOTE 4The use of chromic acid pickles may leave chromate films onthe surface that will reduce the adhesion of the subsequently depositedcoating.5.2.6 Rinse in cold water.5.2.7 Activate in the following solution:3Phosphoric acid, (H3PO4) 20 % by volAmmonium bifluoride (NH4HF

19、2) 105 g/LTemperature 16 to 38CTime 15sto2min5.2.8 Rinse in cold water.5.2.9 Zinc coat in the following solution:Zinc sulfate (ZnSO4H2O) 30 g/LTetrasodium pyrophosphate (Na4P2O7) 120 g/LSodium fluoride (NaF) or 5 g/L orLithium fluoride (LiF) 2 g/LSodium carbonate (Na2CO3)5/L5.2.9.1 Because of the lo

20、w solubility of the tetrasodiumpyrophosphate, it is generally necessary to mix this solution inan elevated temperature from 70 to 85C. It is also advanta-geous to alternately add portions of the zinc sulfate andpyrophosphate. When these ingredients are completely dis-solved, add and dissolve the bal

21、ance of the ingredients in theorder given.NOTE 5Either sodium fluoride or lithium fluoride may be used as aconstituent of this bath. Sodium fluoride is widely used, but requirescareful control. Potassium fluoride is too hygroscopic and should not beused because the variation in water content makes i

22、t impossible to be sureof how much is being added. Lithium fluoride has been found highlydesirable because it is soluble only to the proper concentration level andis self-regulating. Thus, the use of lithium fluoride eliminates the need forfluoride analysis. During bath makeup, 3 g/L lithium fluorid

23、e is added.This small quantity saturates the solution, and an excess suspended in thebath in a canvas or nylon anode bag automatically replaces any fluorideconsumed during the operation.5.2.9.2 Immerse the parts for 3 to 10 min in the solutionoperated at 79 to 85C and agitate mildly. Do not use glas

24、s orfiberglass equipment of any kind. Careful control is essentialfor best results. Maintain the pH between 10.2 and 10.4electrometric (glass electrode) measured at 25C. (WarningThe glass electrode must be used with caution. Do not allowthe electrode to remain in contact with the zincate solution fo

25、rprolonged periods. Inspect and test the electrode regularly toensure that no change has occurred from contact with fluorideion. Colorimetric (paper) methods may be used. However, thecolorimetric readings may vary 60.5 pH units.)5.2.10 Rinse thoroughly in cold water.NOTE 6For alloys M1660, M13120, M

26、13312, or M13310, a doublezinc immersion is required. After step 5.2.10, steps 5.2.7-5.2.10 arerepeated followed by step 5.2.11. It is advisable to use separate solutionsfor steps 5.2.7 and 5.2.9 when the double zinc immersion technique ispracticed.5.2.11 Copper strike in either of the following:Bat

27、h 1:Copper cyanide (CuCN) 38 to 42 g/LPotassium cyanide (KCN) 64.5 to 71.5 g/LPotassium fluoride (KF) 28.5 to 31.5 g/LFree potassium cyanide 7 to 8 g/LpH 9.6 to 10.4Temperature 54 to 60CBath 2:Copper cyanide (CuCN) 38 to 42 g/LSodium cyanide (NaCN) 50 to 55 g/LRochelle salt (KNaC4H4O64H2O) 40 to 48

28、g/LFree sodium cyanide 7 to 8 g/LpH 9.6 to 10.4Temperature 54 to 60C5.2.11.1 Plate the parts about 6 min. Cathode rod agitation issuggested. With either bath make electrical contact quicklywith initial current 5 to 10A/dm2, then lower current to 1 to 2.5A/dm2.5.2.12 Rinse thoroughly in cold water.5.

29、2.13 Dip in diluted acid (1 % by vol sulfuric acid + 99 %by vol water).5.2.14 Rinse in cold water.5.2.15 Apply subsequent electrodeposits or autocatalyticnickel in accordance with standard commercial electroplatingpractice.3Use plastisol-coated racks that are fitted with stain-less steel or phosphor

30、-bronze rack tips.5.3 Autocatalytic Nickel Plating Magnesium:5.3.1 Surface ConditioningSee 5.1.1 and 5.1.2, and 5.2.1-5.2.4.5.3.2 PicklingPickle in (1) chromic acid3as directed in5.2.5.2 or in (2) phosphoric acid3(90 % by vol phosphoricacid + 10 % by vol water) using a lead, glass, ceramic, orrubber

31、-lined tank of polyethylene, polypropylene, or othersuitably corrosion resistant material.5.3.3 Rinse in cold water.5.3.4 Chemical etch in one of the following:Etch 1For Alloys Containing Aluminum:3Chromic acid (CrO3) 120 g/LNitric acid (HNO3) (11 % by vol nitric acid + 89 % by vol water) to make 1L

32、Etch 2For Other Magnesium Alloys:3Chromic acid (CrO3)60g/LNitric acid (HNO3) (9 % by vol nitric acid + 91 % by vol water) to make 1 LStainless steel tank or tank lined with glass, ceramic, polyvinyl chloride, polyeth-lene, or other suitably resistant plastic material.3Magnesium Finishing, The Dow Me

33、tal Products Co., Midland, MI.B480 88 (2010)2Immerse parts 20 to 60 s in solution at room temperature.Rinse thoroughly and proceed immediately to hydrofluoric aciddip.NOTE 7Use the chromic acid pickle where dimensional changecannot be tolerated. Do not use on alloys containing thorium. Forthorium-co

34、ntaining alloys and on other alloys where dimensional changeis not critical, use phosphoric acid pickle. Immerse parts 30 s to 1 min inthe phosphoric acid pickle at 21 to 32C. Metal loss is about 13m/surface. If thorium alloys have critical dimensions, use chromic acidpickle and follow with an immer

35、sion in a strongly alkaline cleaner toremove possible chromate films.5.3.5 Dip3in hydrofluoric acid (5.5 vol % hydrofluoricacid + 94.5 vol % water) using a tank lined with polyvinylchloride, polyethylene, or polypropylene. Immerse parts 10min in solution at room temperature. For treating M11610 orM1

36、1800 use a 20 vol % hydrofluoric acid + 80 vol % watersolution. Transfer to nickel bath immediately after rinsing. Useof ammonium bifluoride (NH4HF2), at 60 to 90 g/L (8 to 12oz/gal) can often be substituted for hydrofluoric acid. Use ofammonium bifluoride eliminates the hazard of handling con-centr

37、ated hydrofluoric acid.NOTE 8The zinc immersion coating plus copper strike can be usedinstead of chemical etching (see Section 1). Follow steps 5.2.5-5.2.11.5.3.6 Nickel plate3in an autocatalytic bath specific formagnesium. The following4is an example of a magnesiumspecific autocatalytic bath:Basic

38、nickel carbonate (2NiCO33Ni(OH)24H2O)10 g/LHydrofluoric acid (HF) (0.6 vol % hydrofluoric acid +79.4 vol % water)Citric acid (C6H8O7) 5.2 g/LAmmonium bifluoride (NH4HF2)10g/LSodium hypophosphite (NaH2PO2H2O) 20 g/LAmmonium hydroxide (NH4OH) (3.9 % by vol ammonium hydroxide + 96.1 % by volwater)Adjus

39、t pH to 5.5 to 6.3Use a tank lined with polyvinyl chloride plastisol, baked-phenolic based enamels, polyethylene, polypropylene, or othersuitably resistant material. Use mild mechanical agitation.Immerse parts in nickel solution operated at 77 to 82C with apH range of 5.5 to 6.3, measured at 25C. Th

40、e bath should befiltered either periodically or continuously. The use of a pumpwhich is sealess or designed for operation in fluoride and withelectroless nickel solution is recommended. To ensure adequatefiltration, the solution should be filtered in excess of 20 tankvolumes per hour through a 5-mic

41、ron filter. The use of aplastic, magnetically coupled pump will eliminate problemswith shaft seals.NOTE 9If heavy electroless nickel deposits are to be applied, the partscan be transferred to the appropriate bath after a thickness of 5 m hasbeen deposited from this bath.5.3.7 Rinse in cold water. Fo

42、r maximum corrosion resis-tance when the above plate is the final deposit, immerse for 10min in (1) chromic acid (CrO3)5(2.5 g/L) or (2) sodiumdichromate (Na2Cr2O72H2O) (120 g/L). Operate both solu-tions at 88 to 100C. Proprietary compounds are availablewhich operate at room temperature.5.3.8 Thorou

43、ghly rinse in cold water and dry. To improveadhesion, bake at 200C for 1 h. The deposit should remainadherent and free of blisters.6. Keywords6.1 activation; cleaning; deoxidizing; magnesium; prepa-ration; strikingASTM International takes no position respecting the validity of any patent rights asse

44、rted 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

45、 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 recei

46、ve 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 Inter

47、national, 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 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or throug

48、h the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).4This bath was patented (U.S. Patent 3,152,009, Oct. 6, 1964, DeLong, H.K.). Itwas assigned to the Dow Chemical Co., Midland, MI. Other autocatalytic plat

49、ingsolutions that may be used are described in U.S. Patent Nos. 2,983,634, May 9,1961, Budininkas, P; 3,121,644, Feb. 18, 1964, Gutzheit, G. and Lee, W.G.; and3,211,578, Oct. 12, 1965, Gutzheit, G. There are also many specialized proprietarybaths available which may be applied directly or after a minimum of 5 m coatinghas been applied from any of the above baths. All the patents listed have expired.5Lee, W.G., U.S. Patent No. 3,088,846, May 7, 1963 (expired).B480 88 (2010)3