ASTM B766-1986(2008) Standard Specification for Electrodeposited Coatings of Cadmium《镉电沉积涂层的标准规范》.pdf

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1、Designation: B 766 86 (Reapproved 2008)Standard Specification forElectrodeposited Coatings of Cadmium1This standard is issued under the fixed designation B 766; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis

2、ion. 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 This specification covers the requirements for

3、electrode-posited cadmium coatings on products of iron, steel, and othermetals.NOTE 1Cadmium is deposited as a coating principally on iron andsteel products. It can also be electrodeposited on aluminum, brass,beryllium copper, copper, nickel, and powder metallurgy parts.1.2 The coating is provided i

4、n various thicknesses up to andincluding 25 m either as electrodeposited or with supplemen-tary finishes.1.3 Cadmium coatings are used for corrosion resistance andfor corrosion prevention of the basis metal part. The as-deposited coating (Type I) is useful for the lowest costprotection in a mild or

5、noncorrosive environment where earlyformation of white corrosion products is not detrimental orharmful to the function of a component. The prime purpose ofthe supplementary chromate finishes (Types II and III) on theelectroplated cadmium is to increase corrosion resistance.Chromating will retard or

6、prevent the formation of whitecorrosion products on surfaces exposed to various environmen-tal conditions as well as delay the appearance of corrosion fromthe basis metal.1.4 Cadmium plating is used to minimize bi-metallic corro-sion between high-strength steel fasteners and aluminum in theaerospace

7、 industry. Undercutting of threads on fastener parts isnot necessary as the cadmium coating has a low coefficient offriction that reduces the tightening torque required and allowsrepetitive dismantling.1.5 Cadmium-coated parts can easily be soldered withoutthe use of corrosive fluxes. Cadmium-coated

8、 steel parts have alower electrical contact resistance than zinc-coated steel. Thelubricity of cadmium plating is used on springs for doors andlatches and for weaving machinery operating in high humidity.Corrosion products formed on cadmium are tightly adherent.Unlike zinc, cadmium does not build up

9、 voluminous corrosionproducts on the surface. This allows for proper functioningduring corrosive exposure of moving parts, threaded assem-blies, valves, and delicate mechanisms without jamming withdebris.2. Referenced Documents2.1 The following standards form a part of this document tothe extent ref

10、erenced herein.2.2 ASTM Standards:2A 165 Specification for Electrodeposited Coatings of Cad-mium on Steel3B117 Practice for Operating Salt Spray (Fog) ApparatusB 183 Practice for Preparation of Low-Carbon Steel forElectroplatingB 201 Practice for Testing Chromate Coatings on Zinc andCadmium Surfaces

11、B 242 Guide for Preparation of High-Carbon Steel forElectroplatingB 253 Guide for Preparation of Aluminum Alloys for Elec-troplatingB 254 Practice for Preparation of and Electroplating onStainless SteelB 281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion C

12、oatingsB 320 Practice for Preparation of Iron Castings for Electro-platingB 322 Guide for Cleaning Metals Prior to ElectroplatingB 343 Practice for Preparation of Nickel for Electroplatingwith NickelB 374 Terminology Relating to ElectroplatingB 487 Test Method for Measurement of Metal and OxideCoati

13、ng Thickness by Microscopical Examination of CrossSectionB 499 Test Method for Measurement of Coating Thick-nesses by the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsB 504 Test Method for Measurement of Thickness of Me-tallic Coatings by the Coulometric Method1This specification is

14、under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.08.04 on Soft Metals.Current edition approved Aug. 1, 2008. Published September 2008. Originallyapproved in 1986. Last previous edition approved in 2003 as B 766 86 (200

15、3).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.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor

16、Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.B 507 Practice for Design ofArticles to Be Electroplated onRacksB 558 Practice for Preparation of Nickel Alloys for Electro-platingB 567 Test Method for Measurement of Coating Thicknessby the Beta Backscatter MethodB 568 Test Method

17、 for Measurement of Coating Thicknessby X-Ray SpectrometryB 571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB 602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB 697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic

18、CoatingsE 8 Test Methods for Tension Testing of Metallic MaterialsF 519 Test Method for Mechanical Hydrogen Embrittle-ment Evaluation of Plating/Coating Processes and ServiceEnvironments2.3 Federal Standard:QQ-P-416 Plating, Cadmium (Electrodeposited)42.4 International Standard:ISO 2082 Metallic Coa

19、tingsElectroplated Coatings ofCadmium on Iron or Steel52.5 Military Standard:MIL-STD-1312 Fasteners, Test Methods63. Terminology3.1 DefinitionsDefinitions of terms used in this specifica-tion are in accordance with Terminology B 374.4. Classification4.1 ClassesElectrodeposited cadmium coatings shall

20、 beclassified on the basis of thickness as follows:Class Minimum Thickness, m25 2512 128855NOTE 2Cadmium coatings thicker than 12 m are normally noteconomical.4.2 TypesElectrodeposited cadmium coatings shall beidentified by types on the basis of supplementary treatmentrequired as follows:4.2.1 Type

21、IAs electrodeposited without supplementarytreatment.4.2.2 Type IIWith supplementary colored chromate treat-ment.4.2.3 Type IIIWith supplementary colorless chromatetreatment.NOTE 3It is strongly recommended that production items be pro-cessed as either Type II or Type III.5. Ordering Information5.1 I

22、n order to make the application of this specificationcomplete, the purchaser needs to supply the following infor-mation to the seller in the purchase order or other governingdocument:5.1.1 The name, designation, and date of issue of thisspecification.5.1.2 Deposit by class and type (4.1 and 4.2).5.1

23、.3 Composition and metallurgical condition of the sub-strate to be coated. Application to high-strength steel parts(6.2).5.1.4 Heat treatment for stress relief, whether it has beenperformed or is required (6.3).5.1.5 Additional undercoat, if required (6.5).5.1.6 Plating process variation, if require

24、d (6.6).5.1.7 Hydrogen embrittlement relief, if required (6.7).5.1.8 Desired color of the Type II film (6.8.2).5.1.9 Location of significant surfaces (7.1.2).5.1.10 Coating luster (7.5).5.1.11 Whether non-destructive or destructive tests are to beused in cases of choice (Note 14).5.1.12 Configuratio

25、n, procedures, and tensile load for hy-drogen embrittlement relief test (9.4, 10.6, SupplementaryRequirements S2, and S3).5.1.13 Whether certification is required (Section 12).5.1.14 Whether supplementary requirements are applicable.6. Materials and Manufacture6.1 Nature of CoatingThe coating shall

26、be essentiallypure cadmium produced by electrodeposition usually from analkaline cyanide solution.6.2 High Tensile Strength Steel Parts Steel parts havingan ultimate tensile strength greater than 1650 MPa (approxi-mately 50 HRC) shall not be plated by electrodeposition unlessauthorized by the purcha

27、ser.6.3 Stress ReliefSteel parts having an ultimate tensilestrength of 1050 MPa (approximately 35 HRC) and above, andthat have been machined, ground, cold-formed, or cold-straightened shall be heat-treated at 190 6 15C for 5 h ormore for stress relief before cleaning and coating.6.4 Preparatory Proc

28、eduresThe basis metal shall be sub-jected to such cleaning procedures as necessary to ensure asurface satisfactory for subsequent electroplating. Materialsused for cleaning shall have no damaging effects on the basismetal resulting in pits, intergranular attack, stress corrosioncracking, or hydrogen

29、 embrittlement. If necessary, cleaningmaterials for steel parts should be evaluated in accordance withMethod F 519.NOTE 4For basis metal preparation, the following standards should beemployed depending upon the metallurgical composition: Practices B 183,B 242, B 253, B 254, B 281, B 320, B 322, B 34

30、3 and B 558.6.5 SubstrateCadmium shall be deposited directly on thebasis metal part without an undercoat of another metal exceptwhen the part is either stainless steel or aluminum and itsalloys. An undercoat of nickel is permissible on stainless steel.With aluminum and aluminum alloys, the oxide lay

31、er shall beremoved and replaced by a metallic zinc layer in accordancewith Guide B 253. For better adherence, a copper strike or a4Available from U.S. Government Printing Office, Washington DC 20402.5Available from American National Standards Institute, 25 W. 43rd St., 4thFloor, New York, NY 10036.6

32、Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.B 766 86 (2008)2nickel coating may be applied to the zinc layer beforeelectroplating with the cadmium.6.6 Plating ProcessThe plating shall be applied after allbasis metal

33、 heat treatments and mechanical operations, such asmachining, brazing, welding, forming, and perforating of thearticle, have been completed.6.7 Hydrogen Embrittlement Relief Steel parts having atensile strength of 1200 MPa (approximately 38 HRC) andhigher shall be baked at 190 6 15C for8hormore with

34、in 4h after electroplating to provide hydrogen embrittlement relief.Electroplated springs and other parts subject to flexure shall notbe flexed, loaded, or used before the hydrogen embrittlementrelief treatment. The baking treatment for hydrogen embrittle-ment relief shall be done before the applica

35、tion of anysupplementary chromate treatment. When specified, freedomfrom embrittlement shall be determined.NOTE 5For high-strength steels, greater than 1300 MPa or approxi-mately 40 HRC, it is strongly recommended that the baking time beextended to 23 h or more to ensure hydrogen embrittlement relie

36、f.NOTE 6Electroplated steel parts, passivated by the baking operationfor hydrogen embrittlement relief, require reactivation before the chro-mate treatment. This application, immersion in a dilute acid solution,should be done as soon as practical. If the chromating solution containssulfuric acid, th

37、en the reactivating solution should be 1 part of sulfuricacid (sp gr 1.83) by volume added to 99 parts of water. If the chromatingsolution contains hydrochloric acid, then the reactivating solution shouldbe 1 part of hydrochloric acid (sp gr 1.16) by volume added to 99 parts ofwater. Duration of imm

38、ersion should be as brief as is consistent with thenature of the work. Separately racked items can be reactivated inapproximately 5 s, whereas a perforated container of barrel-plated partsrequires approximately 15 s.6.8 Chromate Treatment:6.8.1 Chromate treatments for Types II and III shall be donei

39、n or with special aqueous acidic solutions composed ofhexavalent chromium along with certain anions that act ascatalyst or film-forming compounds to produce a continuoussmooth protective film. Chromic acid and nitric acid brightdips shall not be used for treatment to produce chromatecoatings. When p

40、roprietary materials are used for this treat-ment, the instructions of the supplier should be followed.6.8.2 The Type II film color shall range from an iridescentyellow or a thicker, more protective iridescent bronze or brownto the heavier olive drab. It may also be dyed to a desired color.When nece

41、ssary, the color of the film shall be indicated by thepurchaser and specified by the provision of a suitably coloredsample or indicated on the drawing for the part.6.8.3 The absence of color shall not be considered asevidence of lack of Type III film or as a basis for rejection.Presence of clear Typ

42、e III film shall be determined by a spottest as specified in 10.4.6.8.4 Waxes, lacquers, or other organic coatings shall not beused as a substitute for, nor may they be used in conjunctionwith, supplementary treatments when the purpose is to ensureconformance to the salt spray requirements. Waxes an

43、d thelike, may be used to improve lubricity.7. Coating Requirements Coating Requirements7.1 Thickness:7.1.1 The thickness of the coating everywhere on thesignificant surfaces shall conform to the requirements of thespecified class, as defined in 4.1.7.1.2 Significant surfaces are those normally visi

44、ble (di-rectly or by reflection) that are essential to the appearance orserviceability of the article when assembled in normal position;or that can be the source of corrosion products that will defacevisible surfaces on the assembled article. When necessary, thesignificant surfaces shall be indicate

45、d by the purchaser onapplicable drawing of the article, or by the provision ofsuitably marked samples.NOTE 7As heavier coatings are required for satisfactory corrosionresistance than Class 5, allowance should be made in the fabrication ofmost threaded articles, such as nuts, bolts, and similar faste

46、ners withcomplementary threads for dimensional tolerances to obtain necessarycoating build-up. Flat surfaces and certain shielded or recessed areas, suchas root-diameter of threads, have a tendency to exhibit lack of build-upand to be heavier at exposed edges and sharp projections with electrode-pos

47、ited coatings. This trend is also found with vacuum-deposited cad-mium coatings and is in direct contrast with mechanically depositedcoatings.NOTE 8The coating thickness requirements of this specification is aminimum requirement. Variation in thickness from point to point on anarticle is inherent in

48、 electroplating. Therefore, the thickness will have toexceed the specified value at some points on the significant surfaces toensure that it equals or exceeds the specified value at all points. Hence, inmost cases, the average coating thickness of an article will be greater thanthe specified value;

49、how much greater is largely determined by the shapeof the article (see Practice B 507) and the characteristics of the electro-plating process. In addition, the average coating thickness on articles willvary from article to article within a production lot. Therefore, if all of thearticles in a production lot are to meet the thickness requirement, theaverage coating thickness for the production lot as a whole will be greaterthan the average necessary to assure that a single article meets therequirement.7.1.3 For nonsignificant visible surfaces, the minimumth