ASTM B177 B177M-2011(2017) Standard Guide for Engineering Chromium Electroplating《镀铬工程标准指南》.pdf

1、Designation: B177/B177M 11 (Reapproved 2017) Endorsed by AmericanElectroplaters SocietyEndorsed by NationalAssociation of Metal FinishersStandard Guide forEngineering Chromium Electroplating1This standard is issued under the fixed designation B177/B177M; the number immediately following the designat

2、ion indicates the yearof original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by age

3、ncies of the U.S. Department of Defense.1. Scope1.1 This guide provides information about the deposition ofchromium on steel for engineering uses. This is sometimescalled “functional” or “hard” chromium and is usually applieddirectly to the basis metal and is usually thicker than decorativedeposits.

4、1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith

5、the standard.1.3 This guide is not intended as a standardized procedure,but as a guide for obtaining smooth, adherent coatings ofchromium of a desired thickness while retaining the requiredphysical and mechanical properties of the base metals. Speci-fied chromium electrodeposits on ferrous surfaces

6、are definedin Specification B650.1.4 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 limitat

7、ions prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization Te

8、chnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B183 Practice for Preparation of Low-Carbon Steel forElectroplatingB242 Guide for Preparation of High-Carbon Steel for Elec-troplatingB244 Test Method for Measurement of Thickness of AnodicCoatings on Aluminum and of

9、 Other NonconductiveCoatings on Nonmagnetic Basis Metals with Eddy-Current InstrumentsB253 Guide for Preparation of Aluminum Alloys for Elec-troplatingB254 Practice for Preparation of and Electroplating onStainless SteelB281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating

10、 and Conversion CoatingsB320 Practice for Preparation of Iron Castings for Electro-platingB322 Guide for Cleaning Metals Prior to ElectroplatingB481 Practice for Preparation of Titanium and TitaniumAlloys for ElectroplatingB487 Test Method for Measurement of Metal and OxideCoating Thickness by Micro

11、scopical Examination ofCross SectionB499 Test Method for Measurement of Coating Thicknessesby the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsB504 Test Method for Measurement of Thickness of Metal-lic Coatings by the Coulometric MethodB507 Practice for Design of Articles to Be Elect

12、roplated onRacks1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.03 onEngineering Coatings.Current edition approved May 1, 2017. Published May 2017. Originallyapproved in 1955. Last previous edition app

13、roved in 2011 as B177 11. DOI:10.1520/B0177_B0177M-11R17.2For 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.Copy

14、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of Internati

15、onal Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1B558 Practice for Preparation of Nickel Alloys for Electro-platingB568 Test Method for Measurement of Coating Thicknessby X-Ray SpectrometryB571 Practice for Qualitative Adh

16、esion Testing of MetallicCoatingsB578 Test Method for Microhardness of Electroplated Coat-ingsB602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB630 Practice for Preparation of Chromium for Electroplat-ing with ChromiumB650 Specification for Electrodeposited Engineering Chro-m

17、ium Coatings on Ferrous SubstratesB697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB762 Test Method of Variables Sampling of Metallic andInorganic CoatingsB849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen Em

18、brittlementB850 Guide for Post-Coating Treatments of Steel for Reduc-ing the Risk of Hydrogen EmbrittlementB851 Specification for Automated Controlled Shot Peeningof Metallic Articles Prior to Nickel, Autocatalytic Nickel,or Chromium Plating, or as Final FinishF519 Test Method for Mechanical Hydroge

19、n EmbrittlementEvaluation of Plating/Coating Processes and Service En-vironments2.2 Military Standard:3MIL-S-13165B Shot Peening of Metal Parts3. Substrates3.1 Engineering chromium may be plated directly to thesurface of a number of commonly used engineering metalssuch as aluminum, nickel alloys, ca

20、st iron, steels, copper,copper alloys, and titanium. The bond strengths of the chro-mium varies with metallic substrate. Nevertheless, if theprocedures cited in the appropriate references are followed, thebond strength is such that grinding and honing can be con-ducted without delamination of the co

21、ating.3.2 SmoothnessThe smoothness of the material surface tobe electroplated should be adequate to meet the requirementsof the finished product. Chromium electrodeposits do notexhibit leveling, and consequently the surface roughness of theelectrodeposit will always be greater than that of the subst

22、rate.Any mechanical operations that can result in grinding checksor glazing of the metal are detrimental and should be elimi-nated. The required surface smoothness may be obtained bysuitable chemical, mechanical, or electrochemical procedures.Depending upon the thickness of the electrodeposit and th

23、esmoothness required of the electrodeposit, grinding of theelectrodeposit may be required.3.3 Fatigue ConsiderationsCracking that can occur inchromium electrodeposits either as a function of the platingbath chemistry or the plating conditions, or both, or as a resultof grinding of the electrodeposit

24、 can lead to a reduction in thefatigue life of the electroplated part. If this is a designconsideration, the use of mechanical methods such as shotpeening (see Specification B851 or MIL-S-13165C, or both) orautofrettage to compressively stress the surface can increasethe fatigue strength. This shoul

25、d be done after any stress-relieving heat treatment.3.4 High-Strength Steel Stress Relief:3.4.1 All steel parts having an ultimate tensile strength of1000 MPa 150 000 psi, approximately 32 HRC or greater,which may contain residual stress caused by various fabrica-tion operations such as machining, g

26、rinding, straightening, orcold-forming, usually will require one of the stress relief bakesprescribed in Specification B849 prior to electroplating. In allcases, the duration of the bake shall commence from the timeat which the whole of each part attains the specified tempera-ture. This stress relie

27、f is essential if hydrogen embrittlementfrom subsequent operations is to be avoided.3.4.2 Parts having surface-hardened areas that would sufferan unacceptable reduction in hardness by baking in accordancewith Specification B849 may be baked at a lower temperaturebut not less than 130C for a minimum

28、period of 8 h. Shortertimes at higher temperatures may be used, if the resulting lossin surface hardness is acceptable.3.5 OxidationAll possible precautions should be taken toprevent oxidation of the metal surface between the finaloperations of mechanical preparation and electroplating, par-ticularl

29、y with steel substrates. Materials such as aluminum andtitanium have an inherent oxide film on the surface that canonly be removed or minimized just prior to the electroplatingprocess (see 6.1.1 and 6.1.2). When conditions are especiallyunfavorable, definite steps must be taken to meet this importan

30、trequirement, including storage in a noncorrosive environment,or the use of a suitable coating to exclude air and moisture.4. Racks and Anodes4.1 Steel, cast iron, and stainless steel parts to be electro-plated may be racked at any convenient stage in the preparatoryprocess but preferably prior to t

31、he final cleaning and etching.Aluminum, titanium, and certain nickel alloys may need tohave cleaning and etching operations done before racking dueto entrapment of cleaning and etching solutions in the platingrack which can result in adhesion failures due to seepageduring chromium electroplating.4.2

32、 See Practice B507 for guidance on rack design, but notethat while the general principles of good racking as used inother electroplating processes apply, the use of much highercurrent densities and the desirability of securing coatings ofuniform thickness and quality on desired areas require rackcon

33、struction designs and methods that are much more exacting.The design of racks for chromium electroplating on the variousbase metals previously mentioned for functional use shouldprovide for the following to the greatest possible extent.4.2.1 There must be sufficient current-carrying capacity ofboth

34、cathode and anode circuits to all parts of the rack.4.2.2 There must be positive electrical contact to the parts tobe electroplated, to the anodes, and to the tank contact bus bars.3Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094,

35、Attn: NPODS.B177/B177M 11 (2017)24.2.3 There must be uniform current distribution on theparts to be electroplated. This often requires anodes of specialshapes conforming to the shape of the part or area to beelectroplated.4.2.4 It may be necessary to use thieves, robbers, or guards,which are auxilia

36、ry metallic conductors placed near points ofabnormally high current density to attract the current awayfrom such points; and shields, which are parts made ofnonconductive materials and placed to disperse the current inareas where it tends to concentrate unduly.4.2.5 It is important to protect areas

37、that are to remain freeof any chromium electroplate by the use of masks made ofrigid, nonconductive materials placed against the substrate, orstop-offs, which are especially compounded nonconductivetapes, waxes, lacquers, or plastics for the protection of suchsubstrates. Lead and aluminum tapes will

38、 provide a sharp lineof demarcation between coated and uncoated areas with aminimum of buildup.4.2.6 Plugs (conducting and nonconducting) may be used inholes not requiring electroplating to produce a sharp edgewithout grooves around the periphery of the holes.4.2.7 It is very important to remember t

39、hat improperlyapplied stop-off materials or poorly designed racks can entrapacids that can cause corrosion of the basis material or contami-nation of the solutions used in subsequent operations, or both.4.2.8 Construction materials must be used that are suffi-ciently insoluble and noncontaminating t

40、o provide the desiredrack life.4.2.9 Components must be placed in such positions that gasfrom the parts, rack, thieves, masks, and anodes escapes freelyand does not become entrapped so as to prevent electroplatingon areas that should be electroplated.4.3 AnodesLead anodes containing 4 to 6 % antimon

41、y, 4to 7 % tin, or 1 % silver, or a combination thereof, aresatisfactory. Chemical lead is also satisfactory where hardnessand rigidity are not important. However, it tends to form greatquantities of scale that may fall off on the work and causepitting or roughness. Lead wire used for small anodes s

42、houldcontain 0.25 % antimony to obtain the best relationship be-tween rigidity and ductility in close tolerance areas. Lead-sheathed steel, copper, or silver may be used when indicated byrequirements for strength or conductivity. Platinum, platinum-clad niobium, or even steel rods or wire may be use

43、d forinternal electroplating of small holes, but the latter willcontaminate the bath with iron. If the anode contains little or nolead, the reoxidation of trivalent chromium to the hexavalentstate will not take place or will be seriously impaired, whichwill lead to trivalent buildup in the plating s

44、olution and poorresults.4.3.1 Some proprietary baths may require special anodes,which should be recommended by the supplier.5. Cleaning5.1 Parts to be electroplated may be cleaned in accordancewith Practices B183, B242, B254, B281, B320, B322, B481,B558,orB630, or Guide B253.5.2 Mechanical methods o

45、f cleaning steel prior toelectroplating, including abrasive blasting or light grinding, arealso suitable. If parts have been shot-peened to develop acompressively stressed surface, it is important to avoid remov-ing that surface by excessive grinding.6. Deoxidizing and Etching6.1 Prior to chromium e

46、lectroplating, most metals needspecial preparation in order to achieve maximum adhesion ofthe chromium to the substrate. Depending on the type andnature of the metal and prior surface preparation steps, variousdeoxidation and etching methods may be used to activate thesubstrate prior to chromium ele

47、ctroplating.6.1.1 AluminumChromium may be electroplated directlyonto most cast and wrought aluminum materials used forengineering purposes. Guide B253 offers many useful methodsfor preparing aluminum prior to chromium electroplating. Theremoval of the ever-present, tenacious oxide film on the surfac

48、eof aluminum is what makes electroplating difficult. When usingtest methods in which a zinc immersion film is applied to thealuminum surface for protection against oxide formation, thearticle to be plated must enter the chromium-plating solutionunder live current.6.1.2 TitaniumLike aluminum, titaniu

49、m has an ever-present tenacious oxide film that must be removed prior toplating. Practice B481 offers many ways to prepare titaniumprior to chromium electroplating.6.1.3 Nickel AlloysSeveral different activation methodsare available in Practice B558 for the preparation of differentnickel alloys. The main difficulty with these materials whenchromium plating is polarization of the nickel alloy surfaceprior to plating which results in deactivation of the material andskip plating.6.1.4 Copper and Copper AlloysPractice B281 offersmany suitable methods for preparing copper and