1、Designation: B 281 88 (Reapproved 2008)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 () 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 Th
3、is 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 practic
4、e.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 t
5、hispractice.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. Fo
6、r a specifichazard statement, see 6.5.2.2. Referenced Documents2.1 ASTM Standards:2D 322 Test Method for Gasoline Diluent in Used GasolineEngine Oils by Distillation3. Significance and Use3.1 The proper preparation of copper and copper alloysurfaces for electroplating, conversion coating, or autocat
7、alyticplating is often 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
8、from grade chemicals as 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 fr
9、ee of chromium salts, oil, 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, o
10、r heat-treated alloys by 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
11、the end-use properties 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 t
12、horoughly rinsed between 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 Product
13、sStampings and drawnwork 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.1This practice is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings a
14、nd is the direct responsibility of Subcommittee B08.02 onPre Treatment.Current edition approved Aug. 1, 2008. Published September 2008. Originallyapproved in 1953. Last previous edition approved in 2001 as B 281 88 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontac
15、t 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.5.4 Cold-Headed and Prog
16、ressive Die ProductsCold-headed products and progressive die products often requirerelief annealing 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. Abrasiv
17、emethods may be applied as appropriate before cleaning andacid dipping.6. Preparation for Electroplating and ConversionCoating6.1 Outlines of Typical Preparatory Cycles:6.1.1 Vapor degrease or alkaline clean or emulsion soakclean, or tumble clean,6.1.2 Rinse,6.1.3 Alkaline electroclean,6.1.4 Rinse,6
18、.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 are used in the bright dip or
19、alternatives 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 322.6.2 PrecleaningSolvent or sol
20、vent-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 or subsequent coatings, anel
21、ectrolytic 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 cathodic cleaner mayform a smu
22、t 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 cleaners which are used in acc
23、ordance 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 depending on the parts being p
24、rocessed. 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 must be acidified to neutrali
25、ze 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/Lto 100 mL/Lby volume, or hydrochloricacid, 100 mL/L to 200 mL/L by volume. Fluoboric acid, 5
26、0mL/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 mL/L to 50 mL/L by volume, orn
27、itric 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 the firstelectroplating solution
28、 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 not to allow lead toaccumulat
29、e 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 peroxide are used as pickling age
30、nts. 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 surface luster(not mirror bright
31、ness) 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 excess ofhydrochloric acid in
32、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 nickelstrike (seeAppendix X2) may be u
33、sed 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 always necessary to apply a silv
34、erstrike 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 order to obtain adhesion on alloy
35、scontaining 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.B 281 88 (2008)27.4 Gold StrikeIt is always necessary to apply a goldstrike to the work bef
36、ore it enters a good electroplatingsolution. A standard soft gold strike may be employed.8. Keywords8.1 activation; cleaning; copper; deoxidation; preparation;strikingAPPENDIXES(Nonmandatory Information)X1. CLEANING AND PICKLING SOLUTIONSX1.1 Process ChemicalsAll process chemicals are oftechnical gr
37、ade 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 %, density 1.40 g/mLPhosphoric
38、 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 solution concentration o
39、f 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 adjusted to give 100 %T
40、his 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 can be handled in bulk.
41、 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 thesubsequent electropl
42、ate. 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 used fromroom temperat
43、ure 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 copper alloys,proprie
44、tary 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 of brightdips.X1.4.4 Wh
45、en 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 producers ofberyllium copper
46、 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 smooth finish to the part.
47、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 200 mL/L to 350 mL/LH
48、ydrochloric acid 1 mL/LWater To1LAgitate 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 281 88 (2008)3X2. NICKEL STRIKE SOLUTIONSX2.1 Woods
49、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 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/LNicke
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