1、Designation: B 281 88 (Reapproved 2001)Standard Practice forPreparation of Copper and Copper-Base Alloys forElectroplating and Conversion Coatings1This standard is issued under the fixed designation B 281; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 the case of revision, 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 T
3、his practice is intended to serve as a guide for theproper preparation of copper and its alloys for electroplatingand conversion coating. This practice is also suitable for usebefore autocatalytic plating. Only alloys containing at least 50mass % copper are considered within the scope of this practi
4、ce.1.2 The wide variety of methods of mechanical finishing arenot considered strictly as preparation for electroplating orconversion coating and consequently are described onlybriefly.1.3 Details of electroplating and subsequent treatments forapplying conversion coatings are not within the scope of
5、thispractice.1.4 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. F
6、or a specifichazard statement, see 6.5.2.2. Referenced Documents2.1 ASTM Standards:B 322 Practice for Cleaning Metals Prior to Electroplating23. Significance and Use3.1 The proper preparation of copper and copper alloysurfaces for electroplating, conversion coating, or autocatalyticplating is often
7、critical to the performance of the coatings.3.2 This practice outlines procedures required to producesatisfactory coatings on surfaces of copper and copper alloysurfaces.4. Process Chemicals4.1 All process chemicals are of technical grade or better.Acid solutions are prepared from grade chemicals as
8、 listed inAppendix X1.4.2 Purity of WaterHigh quality water is not normallyrequired to make up and maintain the solutions utilized in thispractice. If reused or recycled water from waste treatmentprocesses or from other in-plant sources is to be used, it shouldbe relatively free of chromium salts, o
9、il, wetting agents, orinsoluble materials. Excessively hard water can decrease thelife and performance of many cleaning solutions and makeparts more difficult to rinse completely.5. General Considerations5.1 Removal of OxidesOxides can be removed from asfabricated, annealed, or heat-treated alloys b
10、y abrasive meth-ods such as tumbling, burnishing, and emery set-up wheelpolishing and by chemical methods, such as deoxidizingsolutions, bright dips, and cyanide dips. The choice of methodis dependent on the resultant surface finish required, amount ofoxide to be removed, and the end-use properties
11、of the articlefinished.5.2 Castings and ForgingsCastings and forgings requir-ing abrasive methods to produce a desired surface finish do notnecessarily need pickling or bright dipping. If pickled, brightdipped, or deoxidized, however, castings and other porousparts should be thoroughly rinsed betwee
12、n operations to avoidor minimize staining or stain spots. Castings or forgingsprocessed in solutions containing wetting agents, which are inmany proprietary products or which may be added by theindividual, usually require greater care in rinsing.5.3 Stampings and Drawn ProductsStampings and drawnwor
13、k follow the same rule as castings and forgings except, foreconomy considerations, it may be advisable to pickle ordeoxidize before abrasive finishing if heavy oxides are present.5.4 Cold-Headed and Progressive Die ProductsCold-headed products and progressive die products often requirerelief anneali
14、ng to avoid subsequent season cracking.5.5 Screw Machine ProductsScrew machine productsmay be readily electroplated with only mild cleaning and aciddipping as they are produced from the machines. Abrasivemethods may be applied as appropriate before cleaning andacid dipping.6. Preparation for Electro
15、plating and ConversionCoating6.1 Outlines of Typical Preparatory Cycles:6.1.1 Vapor degrease or alkaline clean or emulsion soak1This practice is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 onPretreatment.Curre
16、nt edition approved March 25, 1988. Published May 1988. Originallypublished as B 281 53 T. Last previous edition B 281 82.2Annual Book of ASTM Standards, Vol 02.05.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.clean, or tumble clean,6.1.2 Rinse,6.1.3 Alkalin
17、e electroclean,6.1.4 Rinse,6.1.5 Acid dip,6.1.6 Rinse, and6.1.7 Electroplate or conversion coat in an acid solution.NOTE 1A bright dip, electropolish, or deoxidization may be addedafter step 6.1.4 or 6.1.2.4 followed by two agitated and running rinsesprior to step 6.1.5.NOTE 2If chromium compounds a
18、re used in the bright dip oralternatives in Note 1, additional steps will be required to ensure completechromium removal from surfaces before any plating process.NOTE 3Additional information on procedures for cleaning of copperor copper alloys prior to electroplating may be found in Practice B 322.6
19、.2 PrecleaningSolvent or solvent-alkali emulsion-soakcleaners can be used if the parts being electroplated can berinsed easily and completely; otherwise, mild alkaline cleanersand vapor degreasing should be used.6.3 ElectrocleaningTo produce the chemically clean sur-face required for electroplating
20、or subsequent coatings, anelectrolytic cleaner may be used with the part as the anode orcathode. Anodic cleaning, particularly of brass, may causeslight tarnishing or etching if applied for a prolonged time(more than a few seconds) or at too high or too low anoperating temperature. A contaminated ca
21、thodic cleaner mayform a smut film on the work. The voltage at the source isusually 6 to 8 V. Separate solutions should be used for anodicand cathodic cleaning. When a part is properly cleaned, it willshow a continuous liquid film upon removal from rinses afteracid dip solutions.NOTE 4Proprietary cl
22、eaners which are used in accordance with thesuppliers recommendations are preferred.NOTE 5The formula of a typical electrolytic cleaner composition isgiven in Appendix X1.6.4 Tumble CleaningTumble cleaning is an alternativeprocess that can be used as a substitute for precleaning orelectrocleaning de
23、pending on the parts being processed. Atypical tumble cleaner is listed in Appendix X1. Proprietarycleaners are available and are generally considered preferable.6.5 Tarnish and Stain Removal, Deoxidizing, and Neutral-izing:6.5.1 Acid DippingAfter the work has been thoroughlycleaned and rinsed, it m
24、ust be acidified to neutralize anyresidual alkali before it enters an electroplating bath. Thus,before nickel, copper, tin, chromium, and similar platingsolutions, an acid dip is used. The most common dips used aresulfuric acid, 50 mL/L to 100 mL/L by volume, or hydrochloricacid, 100 mL/L to 200 mL/
25、L by volume. Fluoboric acid, 50mL/L to 100 mL/L by volume, can be used before fluoborateelectroplating solutions. These solutions are maintained atroom temperature. Leaded copper alloys form insoluble salts ineither sulfuric or hydrochloric acid, and therefore should bepickled in fluoboric acid, 20
26、mL/L to 50 mL/L by volume, ornitric acid, 100 mL/L to 200 mL/L by volume.6.5.2 Cyanide DippingAfter the work has been cleaned,acid pickled, or acid dipped, and thoroughly rinsed, it issometimes immersed in a 15 to 45 g/L sodium cyanide solutionto remove slight tarnish. This step is more common if th
27、e firstelectroplating solution also contains cyanide. (WarningOneshould provide adequate rinsing before and after any cyanide-containing solution before going into an acid solution.)NOTE 6When processing parts containing lead as an alloy constituent,such as free-machining brass, care should be taken
28、 not to allow lead toaccumulate in a cyanide solution beyond 50 mg/L as Pb.6.5.3 Deoxidizing and Bright Dipping:6.5.3.1 Deoxidizing is usually performed to activate thesurface of the part by the removal of the oxide coating. Strongoxidizing solutions such as mixtures of sulfuric acid andhydrogen per
29、oxide are used as pickling agents. Most of thesecompositions are proprietary.6.5.3.2 Bright dipping is primarily used to improve thesurface luster of the work. It also serves as a deoxidizingsolution. While proprietary processes are available one non-proprietary composition which can produce good su
30、rface luster(not mirror brightness) is included in Appendix X1. The brightdipped parts should be rinsed thoroughly by immersion inseveral water rinses with constant agitation. A mild alkalinesolution may be employed to neutralize residual acids beforeimmersion in any cyanide-containing solution. An
31、excess ofhydrochloric acid in the bright dip composition must beavoided; otherwise, a dull finish will result.7. Striking7.1 Copper StrikeIn order to prevent peeling, a copperstrike is used before silver or nickel electroplating of leadedcopper alloys and work that has been soft soldered. A nickelst
32、rike (see Appendix X2) may be used in addition to the copperstrike before silver electroplating. A standard cyanide copperstrike may be employed (see Note 6). All soldered surfaces andthe basis metal must be completely covered with copper. Thisrequires up to 1 min at 3 to 6 V.7.2 Silver StrikeIt is
33、always necessary to apply a silverstrike to the work before it enters a silver electroplatingsolution. The power source should be on and the electricalcircuit connection made (for “live entry) before immersingthe work in either the silver strike or silver electroplatingsolution.7.3 Nickel StrikeIn o
34、rder to obtain adhesion on alloyscontaining nickel, or chromium and iron, or both, one of thenickel strike solutions described in Appendix X1 is used.Additional thicknesses of nickel for the purpose of diffusioncontrol, etc., may be applied.7.4 Gold StrikeIt is always necessary to apply a goldstrike
35、 to the work before it enters a good electroplatingsolution. A standard soft gold strike may be employed.8. Keywords8.1 activation; cleaning; copper; deoxidation; preparation;strikingB 2812APPENDIXES(Nonmandatory Information)X1. CLEANING AND PICKLING SOLUTIONSX1.1 Process ChemicalsAll process chemic
36、als are oftechnical grade or better. Acid solutions are prepared from thefollowing technical grade chemicals:Glycolic acid (CH2OH COOH) 67 mass %, density 1.3 g/mLSulfuric acid (H2SO4) 93 mass %, density 1.83 g/mLHydrochloric acid (HCl) 31 mass %, density 1.16 g/mLNitric acid (HNO3) 67 mass %, densi
37、ty 1.40 g/mLPhosphoric acid (H3PO4) 75 mass %, density 1.5 g/mLFluoboric acid (HBF4) 48 mass %, density 1.38 g/mLX1.2 Tumble CleaningA typical tumble cleaner is asfollows:Mass %Mild soap chips or powder 12.5Trisodium phosphate (Na3PO412H2O) 12.5Sodium carbonate (Na2CO3)75This mixture is used in a so
38、lution concentration of from 30to 45 g/L at 80 to 90C.X1.3 ElectrocleaningA typical formula is as follows:Mass %Sodium carbonate (Na2CO3) 40to50Trisodium phosphate (Na3PO412H2O) 25 to 50Sodium hydroxide (NaOH) 10 to 25Surface active agent (Low foam or No Foam Type) 1Total of individual ingredients a
39、djusted to give 100 %This mixture is used in a solution concentration of 30 to 45g/L.Temperature 60 to 71CCurrent density 1 to 3 A/dm2Time 1 to 3 min cathodic and5 to 10 s anodicX1.4 Acid Pickles:X1.4.1 “Fire Off” or Scale Removal DipThis dip is used to remove heavy oxide layers on small partsthat c
40、an be handled in bulk. A typical example is the followingmixture:Sulfuric acid (50 mL/L) to (300 mL/L)Nitric acid (150 mL/L) to (600 mL/L)Water remainderTemperature 18 to 20CNOTE X1.1Lead sulfate may form on the small globules of leadpresent in leaded brass and can cause porosity and blistering of t
41、hesubsequent electroplate. Diluted nitric acid (without sulfuric acid) hasbeen used successfully, as has fluoboric acid, in scale removal.X1.4.2 For copper and copper-base alloys (except berylliumcopper) to remove oxides, sulfuric acid (100 mL/L to 400mL/L) by volume is used. These solutions may be
42、used fromroom temperature to 80C. Time required may have to be 10min or longer. In some instances the smuts developed inberyllium and tellurium copper can be easily and completelyremoved by a short immersion in 30 to 35 % by vol (22Be)HCl at ambient temperature.X1.4.3 To remove oxides from beryllium
43、 copper alloys,proprietary sulfuric acid/hydrogen peroxide mixtures havebeen found to be preferable to the conventional bright dipsolutions described in X1.4.1 and X1.4.5. Reduced porosity ofthe electroplated coating has been found when these propri-etary deoxidizing solutions are employed instead o
44、f brightdips.X1.4.4 When heat treated, beryllium copper may form aberyllium oxide film. -min dip in a solution of the followingcomposition can be used to ensure complete removal of thisfilm:Sodium hydroxide 500 g/LWater To balanceTemperature 130CNOTE X1.2This procedure is normally used by the produc
45、ers ofberyllium copper alloys.X1.4.5 Nitric-Phosphoric Acid PickleThis pickle is also used to remove oxides and scale. Theparts should be clean and dry before being placed in thesolution.Nitric acid 250 mL/LPhosphoric acid 750 mL/LX1.5 ElectropolishingElectropolishing is used to imparta bright smoot
46、h finish to the part. It is accomplished by makingthe work anodic at 3 to 6 A/dm2in a solution as follows:Glycolic acid 350 mL/LPhosphoric acid 550 mL/LSulfuric acidWater190 mL/LBalanceX1.6 Bright Dip SolutionA formula for a bright dip isgiven as follows:Sulfuric acid 600 mL/L to 750 mL/LNitric acid
47、 200 mL/L to 350 mL/LHydrochloric acid 1 mL/LWater To 1 LAgitate the work constantly while immersed for from 5 to105 s. A mild alkaline solution can be used after rinsing thebright dip solution from the part to ensure neutralization if acyanide plating solution follows.B 2813X2. NICKEL STRIKE SOLUTI
48、ONSX2.1 Woods Nickel StrikeA low pH nickel strike of thefollowing composition may be substituted for a copper strike,especially prior to silver electroplating:Nickel chloride (NiCl26H2O) 240 g/LHydrochloric acid 120 g/LWater balanceCathodic current density 5.4 to 10.8 A/dm2Temperature 18 to 25CTime
49、2 minX2.2 Low pH Sulfamate Nickel StrikeThis solution hasbeen useful when plating on assemblies of mixed alloycomponents where copper or copper alloys have been joined tohigh-nickel steels or other passive metals.Nickel Sulfamate (Ni (SO3NH2)2) 320 g/LNickel as metal 76 g/LBoric acid (H3BO3) 30 g/LWater balancepH (lowered with sulfamic acid) 1.5Cathode current density 210 A/dm2Time 2 minTemperature 18 to 25CX2.3 Glycolate Nickel StrikeGlycolate nickel strike isused on complex parts to increase uniformity and coverage inlow current density
