1、Designation: B 254 92 (Reapproved 2004)e1Endorsed by AmericanElectroplaters SocietyEndorsed by National Associa-tion of Metal FinishersStandard Practice forPreparation of and Electroplating on Stainless Steel1This standard is issued under the fixed designation B 254; the number immediately following
2、 the designation indicates the year oforiginal adoption or, in 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
3、for use by agencies of the Department of Defense.e1NOTEWarning note updated in Section 7.3 in May 2004.1. Scope1.1 Various metals are electrodeposited on stainless steel forcolor matching, lubrication during cold heading, spring-coilingand wire-drawing operations, reduction of scaling at hightempera
4、tures, improvement of wettability (as in fountain pens),improvement of heat and electrical conductance, prevention ofgalling, jewelry decoration, and prevention of superficialrusting.1.2 This practice is presented as an aid to electroplaters andfinishing engineers, confronted with problems inherent
5、in theelectrodeposition of metals on stainless steel. It is not astandardized procedure but a guide to the production of smoothadherent electrodeposits on stainless steel.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
6、 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.2. Referenced Documents2.1 ASTM Standards:2A 380 Practice for Cleaning, Descaling, and Passivation ofStainless Steel Parts, Equipment, and Syste
7、ms3. Nature of Stainless Steel3.1 Because previous metal treatment may have a morepronounced effect on the final finish when stainless steel isbeing electroplated, the metal finisher should become ac-quainted with the fabrication procedure, grade, and mill finishof the stainless steel with which he
8、is working before outlininghis electrodeposition procedure (see Appendix X1).3.2 Stainless steel surfaces are normally resistant to a widevariety of corrosive elements. This property is the result of athin transparent film of oxides present on the surface. Becausethis film rapidly reforms after it h
9、as been stripped off orpenetrated, it protects stainless steel against corrosion. Anadherent electrodeposit cannot be obtained over the oxide filmnormally present on stainless steel. However, once this film isremoved by surface activation and kept from reforming whilethe surface is covered with an e
10、lectrodeposit, any of thecommonly electroplated metals may be electrodeposited suc-cessfully on stainless steel.3.3 Where the finished product is to be subjected to severeexposure, the deposit produced by the proposed electroplatingsequence should be tested under similar exposure conditionsbefore ad
11、option, to determine whether the natural corrosionresistance of the stainless steel has been impaired by thepresence of the electrodeposit.4. Nature of Cleaning4.1 The preparation of stainless steel for electroplatinginvolves three basic steps in the following order:4.1.1 Removal of scale. If scale
12、removal is necessary, one ofthe methods outlined in Appendix X2 may be used (Note 1).See also Practice A 380.4.1.2 Removal of oil, grease, or other foreign material bycleaning, and4.1.3 Activation immediately before electroplating.4.2 PrecleaningRemoval of fabricating lubricants andfinishing compoun
13、ds from the stainless steel may have to beundertaken immediately following the fabrication or finishingoperation (Note 2).4.3 ElectrocleaningAnodic cleaning is generally pre-ferred (Note 3).4.4 Metal LubricantsMetal lubricants such as copper,lead, or cadmium, applied to stainless steel wire for cold
14、heading, wire drawing, or spring forming are removed byimmersion in a solution of 200 mL of concentrated, 67 mass %,nitric acid (density 1.40 g/mL) diluted to 1 L at 50 to 60C. SeePractice A 380.NOTE 1Oil, grease or other fabricating lubricants should be removedby cleaning before heat treating.NOTE
15、2Spray cleaning with a nozzle pressure of 200 to 400 kPa (30to 60 psi) in a power washer, using an alkaline or emulsion-type cleaner,1This practice is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 onPre Treatmen
16、t.Current edition approved April 1, 2004. Published May 2004. Originallyapproved in 1951. Last previous edition approved in 1998 as B 25492 (1998).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandard
17、s 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.is the generally preferred method, especially for the removal of heavydrawing, buffing, or polishin
18、g compounds. Soak cleaning or vapordegreasing may also be used. Extreme examples of such compounds aredrawing or stamping lubricants containing unsaturated oils, which if lefton the surface, form by air-oxidation tenacious films that are very difficultto remove.NOTE 3When brightness is important, al
19、kalinity, current density, andtemperature should be kept as low as the part will permit. This is anessential requirement when cleaning work on racks bearing auxiliary leadanodes or when high chromium alloys (such as UNS Types S44200 andS44600) are being cleaned.5. Cleaning Solutions5.1 The types of
20、solution control, electrodes, heating coils,and rinse tanks normally used for cleaning carbon steel aresatisfactory for stainless steel. Equipment previously used forthe cleaning or processing of carbon steel should not be used.See Practice A 380.6. Racking6.1 The general principles of good racking
21、as used inchromium electroplating processes apply. However, the highelectrical resistance of stainless steel requires rack constructionmethods that minimize potential contact problems and increasethe number of contact points.NOTE 4Because of the high electrical resistance of stainless steel,especial
22、ly in fine-coiled wire articles such as watch bands, chains, jewelry,etc., it is necessary to provide a larger number of contacts. As an example,a watch band 110 mm long made of 1.0-mm diameter wire has been foundto require at least three contacts.7. Activation7.1 After the cleaning operation and be
23、fore the electroplat-ing operation, the parts must be completely activated, that is,the thin transparent film of oxides must be removed from thesurface to be electroplated (Note 5). This film will reform if theparts are allowed to dry or are exposed to oxygen-containingsolutions. For this reason, th
24、e shortest interval practicableshould elapse between the time the parts are removed from theactivating solution and covered by the electrodeposit, unless asimultaneous activation-electroplating procedure is used.NOTE 5The etching practice may be more severe for nondecorativeapplications than for dec
25、orative applications.7.2 The following activating procedures have been used.The procedure selected will depend upon the nature of the partand preceding or subsequent processes (see 7.7). In thefollowing solution formulas, the concentrations are expressedon a volume basis as follows:Liquids: as volum
26、e per litre of solutionSolids: as mass per litre of solution7.3 The commercial grade acids and salts used in theformulas include:Sulfuric acid: 93 mass %; density 1.83 g/mLHydrochloric acid: 31 mass %; density 1.16 g/mLNickel chloride: NiCl26H2OCopper sulfate: CuSO45H2OWarningSulfuric acid should be
27、 slowly added to theapproximate amount of water required with rapid mixing, andthen after cooling, diluted to exact volume.7.4 Cathodic Treatments:7.4.1 Sulfuric acid 50 to 500 mL/LWater to 1 LTemperature roomTime 1 to 5 minCurrent density 0.54 A/dm2Anodes pure lead7.4.2AHydrochloric acid 50 to 500
28、mL/LWater to 1 LTemperature roomTime 1 to 5 minCurrent density 2.15 A/dm2Anodes electrolytic nickel strip or nickelbarASee Patent No. 2,133,996.7.4.3 After immersion in a solution containing 100 to 300 mL/L of hydrochlo-ric acid diluted to 1 L at room temperature for 30 to 60 s, treat cathodically i
29、n:Sulfuric acid 50 to 500 mL/LWater to 1 LTemperature roomCurrent 0.54 to 2.7 A/dm2Anodes pure lead7.5 Immersion Treatments:7.5.1 Immerse in a solution of sulfuric acid containing 200to 500 mL of acid diluted to 1 L at 65 to 80C (with the highertemperature for the lower concentration) for at least 1
30、 min aftergassing starts. If gassing does not start within 1 min after theparts have been immersed, touch them with a carbon-steel baror rod. This activation treatment will produce a dark, adherentsmut that is removed in the electroplating bath. A cathodiccurrent of at least 0.54 A/dm2may be used to
31、 accelerateactivation. Lead anodes are suitable for this solution.7.5.2 Immerse in the following solution:Hydrochloric acid 1 mLSulfuric acid 10 mLWater to 1 LTemperature roomTime 26 sNOTE 6This practice has been used with success for chromiumelectroplating on stainless steel automobile parts in a c
32、onveyorizedprocess. It is not recommended before copper or nickel electroplating.7.6 Simultaneous Activation-Electroplating Treatments:7.6.1 Nickel chlorideA240 gHydrochloric acid 85 mLIron should not exceed7.5 g/ LWater to 1 LTemperature roomElectrodes nickelASee U. S. Patent No. 2,285,548-9.7.6.1.
33、1 Anodic Treatment:Current density 2.2 A/dm2Time 2 min7.6.1.2 Followed by Cathodic Treatment:Current density 2.2 A/dm2Time 6 min7.6.2 Nickel chlorideA240 gHydrochloric acid 126 mLWater to 1 LElectrodes nickelTemperatureBroomCurrent density (cathodic) 5.4 to 21.5 A/dm2Time 2 to 4 minASee U. S. Patent
34、 No. 2,437,409.BBath may require cooling or reduction in hydrochloric acid content iftemperature exceeds 30C.7.6.3 Nickel chloride 30 to 300 g/LB 254 92 (2004)e12Hydrochloric acid 15 to 160 mL/LWater to 1 LElectrodes nickelTemperature roomCurrent density 0.55 to 10.75 A/dm2Time12 to 5 min7.6.4 Hydro
35、chloric acid undiluted commercial grade(7.2)Copper sulfate 0.4 g/LElectrodes nickelTemperature roomCurrent density 4.5 to 6.6 A/dm2Time 1 to 5 minNOTE 7Nickel anode materials containing greater than 0.01 % sulfurare not recommended for use in acid nickel strike baths operated at pH 0.5,or lower, to
36、avoid oxidation of sulfides by hydrochloric acid (see7.6.1-7.6.4, and 7.7).7.7 A combination of more than one type of treatment maybe necessary to ensure a high degree of adhesion. For example,the following has been used in the automotive industry fornickel plating on UNS Type S30200 stainless steel
37、:Sulfuric acid 650 mLWater to 1 LPotential (cathodic) 10 VElectrodes leadTemperature roomTime 2 minFollowed by:Nickel chloride 240 gHydrochloric acid 120 mLWater to 1 LElectrodes nickelTemperature roomTime 2 minCurrent density (cathodic) 16.2 A/dm2This is followed by transfer without rinsing to a Wa
38、tts (orhigher chloride) nickel bath with a pH of 1.5 to 2.0.8. Rinsing8.1 The parts should be transferred to the cold-water rinseand to the plating solution as rapidly as practicable after theactivating procedure; otherwise the surface will passivate itselfand the electrodeposit will not be adherent
39、.8.1.1 The rinse water should be kept slightly acid (approxi-mately pH of 2.5 to 3.5). The acid carryover from the activationoperation will maintain this pH in many instances.8.1.2 In conveyorized operations where trace contaminationof plating solutions with chloride and sulfate from activatingsolut
40、ions will produce an unsatisfactory electrodeposit, spray-rinse operations subsequent to the activation treatment willremove these contaminants.8.1.3 If the simultaneous activation-plating procedure isemployed and nickel plating follows, the intermediate rinseneed only be superficial and the length
41、of transfer time is notso important.9. Electroplating9.1 An adherent electrodeposit of commonly electroplatedmetals (cadmium, copper, brass, chromium, gold, nickel, orsilver) may be electrodeposited directly on stainless steelprovided the surface of the stainless steel is active.NOTE 8Nickel may be
42、electrodeposited at normal current densitiesdirectly on properly activated stainless steel from standard nickel-electroplating solutions if the pH of the solution is between 2 and 4. A pHof 2 is preferred.NOTE 9When a chromium-electroplating solution containing 400 g/Lof chromic acid is used for dec
43、orative chromium electroplating, bettercoverage and a wider bright range is obtained by operating at a currentdensity of 16.2 A/dm2and 49C.NOTE 10A bright nickel electroplate under chromium, preceded byone of the simultaneous activation-electroplating treatments, may often beused to advantage for be
44、tter color matching and elimination of chromiumbuffing.9.2 Where practical, the parts should have the currentapplied during entry into the electroplating solution.10. Stripping10.1 Nitric acid is the preferred stripping solution.10.2 Decorative chromium electrodeposits have beenstripped in a solutio
45、n of 500 mL of concentrated, 31 mass %hydrochloric acid (density 1.16 g/mL) diluted to 1 L at 45 to50C for 1 min.NOTE 11Overstripping will result in etching.NOTE 12Decorative chromium electrodeposits may also be strippedanodically in any alkaline solution.10.3 Cadmium is stripped successfully withou
46、t current byimmersion in a solution of 120 g/L of ammonium nitrate.11. Post Electroplating Operations11.1 Post electroplating operations such as stress relieving,buffing or coloring, and forming or drawing may be applied tostainless steel in the same manner as to any other basis metal,as long as the
47、 natural differences in the characteristic of thestainless steel are taken into consideration. The stainless steelsupplier should be consulted for guidance in regard to thesecharacteristics.12. Test Methods12.1 The methods of testing for thickness, hardness, andadhesion of electrodeposits applied wi
48、th the usual basis metalsmay be employed for similar tests on stainless steel.NOTE 13An exception to this is the determination of the thickness ofchromium on stainless steel by the hydrochloric acid drop method.Because gassing continues after the chromium coating has been pen-etrated, the accuracy o
49、f this method may be questionable for thisapplication.B 254 92 (2004)e13APPENDIXES(Nonmandatory Information)X1. STAINLESS STEEL GRADESX1.1 There are many standard grades and many morespecial grades of stainless steel. Each grade has a specific use,and each may present an individual finishing problem. Thecommon grades are classified as:X1.1.1 Martensitic, or hardenable magnetic chromiumgrades. UNS Types S40300, S40500, S40600, S41000,S41400, S41600, S42000, S43100, S44002, S44003, andS44004 are the more common alloys of this grade.X1.1.2 Ferritic, or nonhar
