ASTM B242-1999(2014) Standard Guide for Preparation of High-Carbon Steel for Electroplating《电镀用高碳钢制备的标准指南》.pdf

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1、Designation: B242 99 (Reapproved 2014) Endorsed by AmericanElectroplaters SocietyEndorsed by NationalAssociation of Metal FinishersStandard Guide forPreparation of High-Carbon Steel for Electroplating1This standard is issued under the fixed designation B242; the number immediately following the desi

2、gnation 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide is intended as an a

3、id 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 this guide, steels containing 0.35 %of carbon or more, and case-hardened low-carbo

4、n 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 introduced problemsnot found in similar operations on low-carbon steel. During the cleani

5、ngand 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. Thepreparation of low-carbon steel for electroplating is covered in PracticeB183.1.2 This g

6、uide does not apply to the electroplating of alloysteel. For methods of chromium electroplating directly on steelsee Guide B177.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address al

7、l of thesafety problems associated with 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 St

8、andards:2B177 Guide for Engineering Chromium ElectroplatingB183 Practice for Preparation of Low-Carbon Steel forElectroplatingB849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen EmbrittlementB850 Guide for Post-Coating Treatments of Steel for Reduc-ing the Risk of Hyd

9、rogen Embrittlement3. Reagents3.1 Purity of ReagentsAll acids and chemicals used in thispractice are technical grade. Acid solutions are based upon thefollowing assay materials:Hydrochloric acid (HCl) 31 mass %, density 1.16 g/mLNitric acid (HNO3) 67 mass %, density 1.40 g/mLSulfuric acid (H2SO4) 93

10、 mass %, density 1.83 g/mL(WarningDilute 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.

11、1 HardnessHigh hardness is a major 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

12、the presence of cracks by a suitable 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

13、 C57 to C62for engineering use4.2 Hydrogen 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

14、without material1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatingsand is the direct responsibility of Subcommittee B08.02 on PreTreatment.Current edition approved Nov. 1, 2014. Published November 2014. Originallyapproved in 1949. Last previous edition appro

15、ved in 2009 as B242 99(2009). DOI:10.1520/B0242-99R14.2For referenced 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.Copyrig

16、ht ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1change in hardness by baking before final pretreatment. For alisting of such hydrogen embrittlement relief bake cycles,consult Guide B850.4.3 Surface OxidationIn order that subsequent treatment

17、sbe facilitated, every reasonable precaution should be takenthroughout 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 atmos

18、phereshould be maintained in the furnace. This copper shall beremoved 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 sl

19、ightoxidation.4.4 Steel QualityThe quality of the steel should 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

20、 wide variety of surfaceconditions are encountered in high-carbon 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

21、fine steel particles resultingfrom the grinding operation. The 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

22、(applicable in all cases).5.1.2 Mechanical treatment of the surface 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

23、be avoided for spring temper andcase-hardened parts. This treatment 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-p

24、lished by an anodic etching treatment in H2SO4(used when-ever possible 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 theelectropl

25、ating solution without its metallic content.5.2 RinsingInadequate 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

26、hy-drogen generation must be designed to operate for a minimumlength 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 us

27、ed underconditions of time, temperature and current density specified 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 ste

28、ps listed in 5.1. Different classes of materials requireselected 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

29、. Preliminary Pretreatment Procedures6.1 ApplicationDegreasing 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

30、tend to prevent the attainment ofthe required quality of the deposit. 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 th

31、e gross contaminants encountered.6.2 PrecleaningSolvent-degreasing 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 pa

32、rts that are to be barrelelectroplated. Electrolytic cleaning should 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 t

33、he final pretreat-ment cycle, or both. For a listing of typical stress-relief bakes,consult Specification B849.6.4 Mechanical TreatmentThe purpose of mechanicaltreatment is to reduce subsequent acid pickling to a minimum.Where mechanical treatment has been accomplished withprecision, it is sometimes

34、 possible to eliminate acid picklingentirely, thus improving the 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,

35、or by sand, grit, or vapor blasting.These operations should be 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 criticalimportance, for example, in chromium

36、 electroplating for engi-neering use.B242 99 (2014)27. Final Pretreatment Procedures7.1 ApplicationFinal cleaning, oxide removal, and anodicacid treatment are fundamental steps required for preparinghigh-carbon steel for electroplating. These pretreatment stepsare designed to assist in the control o

37、f hydrogen embrittlementand in securing the maximum adhesion 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 hydrogenemb

38、rittlement that is likely to result from cathodic cleaning.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

39、 of contaminants. In all cases it shouldbe preceded by heavy-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

40、period not exceeding 2 min.7.2.4 On removal from the cleaner, 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 e

41、ach processing step if the best resultsin electroplating high-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 Wa

42、rm to hot rinses should be used following alkalinesolutions 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

43、 solution in the next processing step is cold. In no caseshould 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 t

44、rouble in the electroplating of high-carbonsteel.7.4 Hydrochloric 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 o

45、f oxide present. The use of H2SO4insteadof HCl is not recommended 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 cautio

46、n must be exercised in the use ofinhibitors where they are 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 r

47、esults in the presence of smut, thesmut must be removed before 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

48、dip after the rinsefollowing the acid treatment. A concentration 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 ro

49、om temperature.An alternative treatment for a somewhat lighter 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 smutf