1、Designation: B 480 88 (Reapproved 2006)Standard Guide forPreparation of Magnesium and Magnesium Alloys forElectroplating1This standard is issued under the fixed designation B 480; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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 guide describes two processes used for plating onmagnesium and magnesium alloys: direct electroless nic
3、kelplating 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 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the us
4、er 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, see 5.1.1 and 5.2.9.2.2. Referenced Documents2.1 ASTM Standards:2B 322 Guide for Cleaning Metals Prior to Electroplating3.
5、 Significance and Use3.1 Metals are electroplated on magnesium for variouspurposes: solderability, RF grounding, hermetic sealing, wearresistance, corrosion resistance, appearance, and electricalconductivity, for example. Because magnesium is covered witha naturally occurring oxide film, usual proce
6、dures 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 technical grade. Acid and base solutions arebased on the following assay materials:Ammonium hydroxide (NH4OH) 30 mass %, densit
7、y 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) 85 mass %, density 1.689 g/L4.2 Purity of WaterAll water used for solutions, whethernew or recycled, should be monitore
8、d 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-ished surfaces. Tumble and burnish small parts.Acid pickle theparts after use of wire brushing or steel wool. (WarningBecau
9、se of the high flammability of powdered magnesium,special precautions against fire are important. Polishing andbuffing lathes should be kept scrupulously clean. Dust fromgrinding in and around lathes should be swept up and placed inclosed containers for proper disposal. Exhaust systems shouldbe clea
10、ned frequently and the residues handled similarly. Ifabrasives are used in tumble finishing, similar precautionarytechniques should be used for the solids from the abrasiveslurry.)5.1.2 ChemicalRemove oil and grease in an alkaline soakcleaner. Remove other soils and coatings in suitable acidpickling
11、 solutions.NOTE 1General information on the cleaning of metals is given inPractice B 322.5.2 General Electroplating Procedure:5.2.1 Remove oil, grease, and other soils left from preplat-ing procedures by soak cleaning in an alkaline cleaner suitablefor magnesium.5.2.2 Rinse in cold water.NOTE 2As ge
12、nerally 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 in water, ambientwater temperatures may be too low for effective rinsing. In thoseinstances, the rinse water may need
13、to be heated. A minimum temperatureof 16C is recommended for effective rinsing.5.2.3 Electroclean 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.1This guide is under the jurisdiction of ASTM Committee B08 on
14、 Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.02 on PreTreatment.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 1968. Last previous edition approved in 2001 as B 480 88 (2001).2For referenced ASTM standards, visit the ASTM w
15、ebsite, 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 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United S
16、tates.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 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 di
17、mensional 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/LTemperature 16 to 93CTime 2to10minNOTE 4The use of chromic acid pickles may leave chromate films onthe surface that will reduce the adhesion of the subse
18、quently depositedcoating.5.2.6 Rinse in cold water.5.2.7 Activate in the following solution:3Phosphoric acid, (H3PO4) 20 % by volAmmonium bifluoride (NH4HF2) 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/LTe
19、trasodium 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 low solubility of the tetrasodiumpyrophosphate, it is generally necessary to mix this solution inan elevated temperature from 70 to 85C. It is also
20、 advanta-geous to alternately add portions of the zinc sulfate andpyrophosphate. When these ingredients are completely dis-solved, add and dissolve the balance of the ingredients in theorder given.NOTE 5Either sodium fluoride or lithium fluoride may be used as aconstituent of this bath. Sodium fluor
21、ide is widely used, but requirescareful control. Potassium fluoride is too hygroscopic and should not beused because the variation in water content makes it impossible to be sureof how much is being added. Lithium fluoride has been found highlydesirable because it is soluble only to the proper conce
22、ntration level andis self-regulating. Thus, the use of lithium fluoride eliminates the need forfluoride analysis. During bath makeup, 3 g/L lithium fluoride is added.This small quantity saturates the solution, and an excess suspended in thebath in a canvas or nylon anode bag automatically replaces a
23、ny 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 glass orfiberglass equipment of any kind. Careful control is essentialfor best results. Maintain the pH between 10.2 and 10.4electrometric (glass ele
24、ctrode) measured at 25C. (WarningThe glass electrode must be used with caution. Do not allowthe electrode to remain in contact with the zincate solution forprolonged periods. Inspect and test the electrode regularly toensure that no change has occurred from contact with fluorideion. Colorimetric (pa
25、per) 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, M13312, 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
26、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:Bath 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
27、 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 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
28、 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.5.2.13 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 auto
29、catalyticnickel in accordance with standard commercial electroplatingpractice.3Use plastisol-coated racks that are fitted with stain-less steel or phosphor-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
30、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-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
31、 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 1LEtch 2For Other Magnesium Alloys:3Chromic acid (CrO3)60g/LNitric acid (HNO3) (9 % by vol nitric acid + 91 % by vol water) to make 1 LStainless st
32、eel tank or tank lined with glass, ceramic, polyvinyl chloride, polyeth-lene, or other suitably resistant plastic material.Immerse 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 cha
33、nge3Magnesium Finishing, The Dow Metal Products Co., Midland, MI.B 480 88 (2006)2cannot be tolerated. Do not use on alloys containing thorium. Forthorium-containing alloys and on other alloys where dimensional changeis not critical, use phosphoric acid pickle. Immerse parts 30 s to 1 min inthe phosp
34、horic 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 immersion in a strongly alkaline cleaner toremove possible chromate films.5.3.5 Dip3in hydrofluoric acid (5.5 vol % hydrofluoricacid + 94.5 vol % wat
35、er) using a tank lined with polyvinylchloride, polyethylene, or polypropylene. Immerse parts 10min in solution at room temperature. For treating M11610 orM11800 use a 20 vol % hydrofluoric acid + 80 vol % watersolution. Transfer to nickel bath immediately after rinsing. Useof ammonium bifluoride (NH
36、4HF2), 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-centrated hydrofluoric acid.NOTE 8The zinc immersion coating plus copper strike can be usedinstead of chemical etching (see Section 1). Follow steps
37、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 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/LAmm
38、onium bifluoride (NH4HF2)10g/LSodium hypophosphite (NaH2PO2H2O) 20 g/LAmmonium hydroxide (NH4OH) (3.9 % by vol ammonium hydroxide + 96.1 % by volwater)Adjust pH to 5.5 to 6.3Use a tank lined with polyvinyl chloride plastisol, baked-phenolic based enamels, polyethylene, polypropylene, or othersuitabl
39、y 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. The bath should befiltered either periodically or continuously. The use of a pumpwhich is sealess or designed for operation in fluoride and withel
40、ectroless nickel solution is recommended. To ensure adequatefiltration, the solution should be filtered in excess of 20 tankvolumes per hour through a 5-micron filter. The use of aplastic, magnetically coupled pump will eliminate problemswith shaft seals.NOTE 9If heavy electroless nickel deposits ar
41、e 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. For 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) sodiumd
42、ichromate (Na2Cr2O72H2O) (120 g/L). Operate both solu-tions at 88 to 100C. Proprietary compounds are availablewhich operate at room temperature.5.3.8 Thoroughly rinse in cold water and dry. To improveadhesion, bake at 200C for 1 h. The deposit should remainadherent and free of blisters.6. Keywords6.
43、1 activation; cleaning; deoxidizing; magnesium; prepa-ration; strikingASTM International 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 a
44、ny 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
45、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 recei
46、ved 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
47、 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 through the ASTM website(www.astm.org).4This bath was patented (U.S. Patent 3,152,009, Oct. 6, 1964, DeLong, H.K.). Itwas assigned to the Dow Chemical
48、 Co., Midland, MI. Other autocatalytic platingsolutions 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).B 480 88 (2006)3
