1、Designation: B480 88 (Reapproved 2017)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 5.2.9.2.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization
6、 TechnicalBarriers to Trade (TBT) Committee.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
7、resistance, appearance, 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 in t
8、hisguide are of technical grade. Acid and base solutions are basedon 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/L
9、Phosphoric acid (H3PO4) 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
10、 smooth, highly pol-ished 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 cle
11、an. Dust fromgrinding in 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 fr
12、om the abrasiveslurry.)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 ot
13、her soils left from preplat-ing procedures by soak cleaning in an alkaline cleaner suitablefor magnesium.5.2.2 Rinse in cold water.1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.02 on PreTreatment.Cur
14、rent edition approved May 1, 2017. Published May 2017. Originallyapproved in 1968. Last previous edition approved in 2010 as B480 88(2010). DOI:10.1520/B0480-88R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Boo
15、k 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 StatesThis international standard was developed in accordance with internationally recogni
16、zed 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.1NOTE 2As generally used in rinsing terminology, cold water refers
17、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 to be heated. A minimum temperatureof 16C is recommende
18、d 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.5.2.5 Pickle in one of the following solutions:5.2.5.1 Ferric Nitrate Pickle:3Chromic acid (CrO3) 180 g/LFerric nitra
19、te (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 dimensional change can be tolerated, use of thechromic acid pickle in 5.2.5.2 is recommended.5.2.5.2 Chromic Acid Pickle:3Chr
20、omic 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 subsequently depositedcoating.5.2.6 Rinse in cold water.5.2.7 Activate in the following solution:3Phosphoric acid, (H3PO4) 20 %
21、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/LTetrasodium pyrophosphate (Na4P2O7) 120 g/LSodium fluoride (NaF) or 5 g/L orLithium fluoride (LiF) 2 g/LSodium carbonate (Na2
22、CO3)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 advanta-geous to alternately add portions of the zinc sulfate andpyrophosphate. When these ingredients are completelydisso
23、lved, 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 fluoride is widely used, but requirescareful control. Potassium fluoride is too hygroscopic and should not beused because the vari
24、ation 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 concentration level andis self-regulating. Thus, the use of lithium fluoride eliminates the need forfluoride analysis. During bath
25、 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 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 a
26、gitate 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 electrode) measured at 25C. (WarningThe glass electrode must be used with caution. Do not allowthe electrode to remain in contac
27、t with the zincate solution forprolonged 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.NOT
28、E 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 to use separate solutionsfor steps 5.2.7 and 5.2.9 when the double zinc immersion technique ispracticed.5.2.11 Copper strike
29、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 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
30、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 either bath make electrical contact quicklywith initial current 5 to 10A/dm2, then lower current to 1 to 2.5A/dm2.5.2.12 Rin
31、se 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 autocatalyticnickel in accordance with standard commercial electroplatingpractice.3Use plastisol-coated racks that are fitted wit
32、h 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 in (1) chromic acid3as directed in5.2.5.2 or in (2) phosphoric acid3(90 % by vol phosphoricacid + 10 % by vol water) using a
33、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 the following:Etch 1For Alloys Containing Aluminum:3Chromic acid (CrO3) 120 g/LNitric acid (HNO3) (11 % by vol nitric acid +
34、 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 steel tank or tank lined with glass, ceramic, polyvinyl chloride, polyeth-lene, or other suitably resistant plastic material.3M
35、agnesium Finishing, The Dow Metal Products Co., Midland, MI.B480 88 (2017)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 change cannotbe tolerated. Do not use on alloys con
36、taining thorium. For thorium-containing alloys and on other alloys where dimensional change is notcritical, use phosphoric acid pickle. Immerse parts 30 s to 1 min in thephosphoric acid pickle at 21 to 32C. Metal loss is about 13 m/surface.If thorium alloys have critical dimensions, use chromic acid
37、 pickle andfollow with an immersion in a strongly alkaline cleaner to remove possiblechromate 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 temper
38、ature. For treating M11610 orM11800 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 t
39、he 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 5.2.5 5.2.11.5.3.6 Nickel plate3in an autocatalytic bath specific formagnesium. The following4is an example of a magnesiumspe
40、cific 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/LAmmonium bifluoride (NH4HF2)10g/LSodium hypophosphite (NaH2PO2H2O) 20 g/LAmmonium hydroxide (NH4OH) (3.9 % by vol ammonium hydro
41、xide + 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 othersuitably resistant material. Use mild mechanical agitation.Immerse parts in nickel solution operated at 77 to 82C with apH range of
42、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 withelectroless nickel solution is recommended. To ensure adequatefiltration, the solution should be filtered in excess of 20 tankv
43、olumes 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 are to be applied, the partscan be transferred to the appropriate bath after a thickness of 5 m hasbeen deposited from this bat
44、h.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) sodiumdichromate (Na2Cr2O72H2O) (120 g/L). Operate both solu-tions at 88 to 100C. Proprietary compounds are availablewhich operate a
45、t 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. Keywords6.1 activation; cleaning; deoxidizing; magnesium; prepa-ration; strikingASTM International takes no position respecting the val
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