ASTM B242-1999(2004)e1 Standard Guide for Preparation of High-Carbon Steel for Electroplating《电镀用高碳钢制备的标准实施规范》.pdf

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1、Designation: B 242 99 (Reapproved 2004)e1Endorsed by AmericanElectroplaters SocietyEndorsed by NationalAssociation of Metal FinishersStandard Guide forPreparation of High-Carbon Steel for Electroplating1This standard is issued under the fixed designation B 242; the number immediately following the d

2、esignation 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.e1NOTEThe Warning note in Section 3.1

3、was editorially updated in October 2004.1. Scope1.1 This guide is intended as an aid in establishing andmaintaining a preparatory cycle for electroplating on high-carbon steel (Note 1) producing a minimum of hydrogenembrittlement and maximum adhesion of the electrodepositedmetal. For the purpose of

4、this guide, steels containing 0.35 %of carbon or more, and case-hardened low-carbon steel, aredefined as high-carbon steels. There is no generally recognizeddefinite carbon content dividing high from low-carbon steelsfor electroplating purposes.NOTE 1Electroplating of plain high-carbon steel introdu

5、ced problemsnot found in similar operations on low-carbon steel. During the cleaningand electroplating cycle, high-carbon steel differs from low-carbon steel inregard to its greater tendency to become embrittled and the greaterdifficulty in obtaining maximum adhesion of the electrodeposit. Theprepar

6、ation of low-carbon steel for electroplating is covered in PracticeB 183.1.2 This guide does not apply to the electroplating of alloysteel. For methods of chromium electroplating directly on steelsee Guide B 177.1.3 This standard does not purport to address all of thesafety problems associated with

7、its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use. For a specific hazards statement, see3.1.2. Referenced Documents2.1 ASTM Standards:2B 177 Guide for Engineering Chr

8、omium ElectroplatingB 183 Practice for Preparation of Low-Carbon Steel forElectroplatingB 849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen EmbrittlementB 850 Guide for Post-Coating Treatments of Steel for Re-ducing the Risk of Hydrogen Embrittlement3. Reagents3.1 Pu

9、rity of ReagentsAll acids and chemicals used inthis practice are technical grade. Acid solutions are based uponthe following assay materials:Hydrochloric acid (HCl) 31 mass %, density 1.16 g/mLNitric acid (HNO3) 67 mass %, density 1.40 g/mLSulfuric acid (H2SO4) 93 mass %, density 1.83 g/mL(WarningDi

10、lute sulfuric acid by slowly adding it to theapproximate amount of water required with rapid mixing. Aftercooling, bring the mixture to exact volume.)3.2 Purity of WaterUse ordinary industrial or potablewater for preparing solutions and rinsing.4. Nature of Steel4.1 HardnessHigh hardness is a major

11、cause of crackingof the steel during or after electroplating. The recommendedmaximum hardness range for classes of products depends ontheir geometry and service requirements (Note 2). Parts hard-ened by heat treatment should be inspected before electroplat-ing for the presence of cracks by a suitabl

12、e method, such asmagnetic or fluorescent powder inspection.NOTE 2Some examples of parts and Rockwell hardness ranges are asfollows:Rockwell Hard-ness RangeSprings C45 to C48Spring washers C45 to C53Small instrument parts C52 to C55Parts to be chromium electroplated C57 to C62for engineering use4.2 H

13、ydrogen EmbrittlementDifficulties resulting fromhydrogen embrittlement increase with increasing hardness,whether produced by heat treatment or cold work. Difficulties,during or after electroplating of hardened high-carbon steelparts, may in some cases be minimized without material1This guide is unde

14、r the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.02 on PreTreatment.Current edition approved Oct. 1, 2004. Published October 2004. Originallyapproved in 1949. Last previous edition approved in 1999 as B 242 99.2For refere

15、nced ASTM standards, visit the ASTM website, 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

16、Conshohocken, PA 19428-2959, United States.change in hardness by baking before final pretreatment. For alisting of such hydrogen embrittlement relief bake cycles,consult Guide B 850.4.3 Surface OxidationIn order that subsequent treatmentsbe facilitated, every reasonable precaution should be takenthr

17、oughout the processing to limit oxidation or scale formation.In particular cases pre-electroplating with copper to a mini-mum thickness of 13 m may assist in maintaining a preferredsurface through the heat treatment. A nonoxidizing atmosphereshould be maintained in the furnace. This copper shall ber

18、emoved prior to the regular electroplating cycle. Care shouldbe used in oil-quenching parts heat treated in a salt bath, toprevent the charring effect that can be caused by salt-bathdrag-out. Proper lead-bath quenching results in only slightoxidation.4.4 Steel QualityThe quality of the steel should

19、be char-acteristic of the requirement of the product and the electroplat-ing operation. The steel should be free of injurious surfacedefects, and of at least average cleanliness.5. Preparation of Steel, General5.1 Preparatory TreatmentsA wide variety of surfaceconditions are encountered in high-carb

20、on steel articles to beelectroplated. The surface may require the removal of one ormore of the following contaminants: grease, oil or drawingcompounds, burned-in oil scale, light to heavy treatment scale,permeable oxide films, emery and fine steel particles resultingfrom the grinding operation. The

21、removal of such contaminantsis accomplished by one or more of the following pretreatmentprocedures where applicable:5.1.1 Substantial removal of oil, grease, and caked-on dirtby precleaning before the part enters the electroplating cycle(applicable in all cases).5.1.2 Mechanical treatment of the sur

22、face by tumbling, sandor grit blasting, vapor blasting, or grinding (optional).5.1.3 Final and complete anodic cleaning in an electrolyticalkali cleaner.5.1.4 Acid treatment in HCl to remove the last trace of oxideand scale. This should be avoided for spring temper andcase-hardened parts. This treat

23、ment also removes residualtraces of lead that may be present following proper lead-bathquenching.5.1.5 Smut removal by cyanide dipping or by anodic treat-ment in cyanide or alkali.5.1.6 Final preparation for electroplating may be accom-plished by an anodic etching treatment in H2SO4(used when-ever p

24、ossible in the interest of high yield and adhesion).5.1.7 Conditioning of the surface to be electroplated may beaccomplished, where necessary for the electroplating process,by a short dip or rinse in a solution equivalent to theelectroplating solution without its metallic content.5.2 RinsingInadequa

25、te rinsing after each solution treat-ment step is the recognized cause of a large portion ofelectroplating difficulties. Not enough rinsing is characteristicof most pretreatment cycles.5.3 Pretreatment TimeAll processing steps involving hy-drogen generation must be designed to operate for a minimuml

26、ength of time, to avoid hydrogen embrittlement of the high-carbon steel.5.4 ControlAll pretreatment steps should be carried outwith solutions that are maintained in good working conditionby control of composition and contaminants, and used underconditions of time, temperature and current density spe

27、cified tomeet the requirement of the work being processed.5.5 Pretreatment Cycle DesignDepending upon the re-quirements for the particular high-carbon steel parts to beelectroplated, a minimum cycle should be selected from thegeneral steps listed in 5.1. Different classes of materials requireselecte

28、d process steps combined into pretreatment cycles ofgreater or less complexity according to the condition andproperties of the material. The minimum number of stepsnecessary to accomplish the electroplating satisfactorily isrecommended.6. Preliminary Pretreatment Procedures6.1 ApplicationDegreasing

29、and mechanical surface treat-ment are necessary only where the high-carbon steel parts arecontaminated to such an extent that otherwise the burdenimposed on the pretreatment cycle would impair its efficiency,increase its complexity, and tend to prevent the attainment ofthe required quality of the de

30、posit. The overall cost of theelectroplating process is usually reduced by using the prelimi-nary treatments where applicable. Oil, grease, dirt, drawingcompounds, burnt-in oil, heavy scale, and emery and steelparticles are typical of the gross contaminants encountered.6.2 PrecleaningSolvent-degreas

31、ing with clean solvent,spray-washing, or emulsion-cleaning, followed by electrolyticor soak-alkali cleaners are recommended. The former types arepreferred to reduce the burden on the alkali treatments.Soak-alkali cleaning is usual for parts that are to be barrelelectroplated. Electrolytic cleaning s

32、hould always be anodicwhere the control of embrittlement is a problem.6.3 Stress Relief TreatmentIt is recommended that hard-ened high-carbon steel parts receive a stress-relief bake beforethe parts are mechanically pretreated or enter the final pretreat-ment cycle, or both. For a listing of typical

33、 stress-relief bakes,consult Specification B 849.6.4 Mechanical TreatmentThe purpose of mechanicaltreatment is to reduce subsequent acid pickling to a minimum.Where mechanical treatment has been accomplished withprecision, it is sometimes possible to eliminate acid picklingentirely, thus improving t

34、he control of hydrogen embrittlement.When required, mechanical treatment of small parts is besteffected by tumbling. All scaled and nearly all oil-quenchedmaterials require mechanical cleaning such as by tumblingwith or without abrasive, or by sand, grit, or vapor blasting.These operations should be

35、 carried out so as to avoid severeroughening of the surface with accompanying notch effect.One resorts to grinding in certain cases where the surfacesmoothness or dimensions of the parts are of critical impor-tance, for example, in chromium electroplating for engineeringuse.7. Final Pretreatment Pro

36、cedures7.1 ApplicationFinal cleaning, oxide removal, and anodicacid treatment are fundamental steps required for preparinghigh-carbon steel for electroplating. These pretreatment stepsB 242 99 (2004)e12are designed to assist in the control of hydrogen embrittlementand in securing the maximum adhesio

37、n of the electroplatedcoating.7.2 Electrolytic Anodic Cleaning:7.2.1 All work, except work to be barrel electroplated,should preferably be cleaned in an electrolytic anodic alkalinecleaner. Anodic cleaning is recommended to avoid hydrogenembrittlement that is likely to result from cathodic cleaning.

38、 Anexception is barrel work which, because of the work size, ispreferably cleaned by soaking or tumbling in an alkalinecleaning solution without the use of current.7.2.2 The purpose of this cleaning step is to removecompletely the last traces of contaminants. In all cases it shouldbe preceded by hea

39、vy-duty precleaning as covered in 6.2.7.2.3 The electrolytic anodic cleaner should be used at atemperature of 90C or higher, and at a current density of 5A/dm2or higher, in order that the required degree of cleanli-ness be obtained in a time period not exceeding 2 min.7.2.4 On removal from the clean

40、er, the work should bethoroughly rinsed, first with water warmed to 50C, and then ina cold-water spray at room temperature, prior to the acid dip.7.3 Rinsing:7.3.1 The most thorough fresh-water rinsing operation pos-sible is mandatory after each processing step if the best resultsin electroplating h

41、igh-carbon steel are to be obtained. Thepurpose of rinsing is to eliminate drag-over by completeremoval of the preceding solution from the surface of the work.Many existing commercial operations are characterized byinadequate rinsing.7.3.2 Warm to hot rinses should be used following alkalinesolution

42、s or where the subsequent processing solution is hot.The rinse temperature should not be so high as to induce dryingof the steel surface between processing steps. Room tempera-ture rinses are suitable for use following acid solutions wherethe solution in the next processing step is cold. In no cases

43、hould very cold water be used for rinsing.7.3.3 The recommended rinsing practice includes the use ofan immersion rinse, always followed by a spray rinse of freshwater at the required temperature. Not using a spray rinsing isan invitation to trouble in the electroplating of high-carbonsteel.7.4 Hydro

44、chloric Acid TreatmentThe purpose of the HCltreatment is to remove completely the last trace of oxide fromthe surface of the high-carbon steel. The intensity of the HCltreatment should be held to the minimum required by thenature and amount of oxide present. The use of H2SO4insteadof HCl is not reco

45、mmended for descaling high-carbon steelbecause of its smut-forming tendency, in spite of the somewhatlowered tendency to rusting of H2SO4-treated surfaces. Theaddition of wetting agents to the HCl solution is not recom-mended. Care and caution must be exercised in the use ofinhibitors where they are

46、 required, because they sometimesinterfere with adhesion. Inhibitors are of benefit only in specialcases where surface finish and dimensions are of primeimportance.7.5 Treatment for Smut RemovalWhen the HCl treatmentof the high-carbon steel results in the presence of smut, thesmut must be removed be

47、fore the surface is electroplated.Light oxides formed on exposure to air after acid treatmentmust likewise be removed. This can be done by an anodiccyanide or alkaline treatment. Air-formed oxide, if not tooheavy, can be removed by a cyanide dip after the rinsefollowing the acid treatment. A concent

48、ration of 22 g/L ofNaCN is sufficient for the cyanide dip. Where a severe smutcondition exists, it can be eliminated by a12 to 1-min anodictreatment at 1.5 to 2 A/dm2in a solution of a NaCN of thenoncritical concentration of 45 g/L used at room temperature.An alternative treatment for a somewhat lig

49、hter smut conditionis electrolytic anodic treatment in the noncyanide alkalinecleaning solution (6.3) above 70C, for 15 to 30 s at 2.5 to 5A/dm2. The current density is not critical.7.6 Anodic Acid Etching:7.6.1 The use of an anodic acid etch and subsequent rinse asfinal steps in the preparation for electroplating of high-carbonsteel is of importance in securing adhesion. Without such ananodic treatment, poor adhesion may occur. The anodic acidtreatment is capable of removing a small amount of smutformed by the preceding HCl treatment; more substantialamou