1、Designation: B 766 86 (Reapproved 2003)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 (e) 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
4、in 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 theaerospac
7、e 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-coate
8、d 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 u
9、p 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 re
10、ferenced herein.2.2 ASTM Standards:A 165 Specification for Electrodeposited Coatings of Cad-mium on Steel2B 117 Practice for Operating Salt Spray (Fog) Apparatus3B 183 Practice for Preparation of Low-Carbon Steel forElectroplating4B 201 Practice for Testing Chromate Coatings on Zinc andCadmium Surfa
11、ces4B 242 Practice for Preparation of High-Carbon Steel forElectroplating4B 253 Guide for Preparation of Aluminum Alloys for Elec-troplating4B 254 Practice for Preparation of and Electroplating onStainless Steel4B 281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Co
12、nversion Coatings4B 320 Practice for Preparation of Iron Castings for Electro-plating4B 322 Practice for Cleaning Metals Prior to Electroplating4B 343 Practice for Preparation of Nickel for Electroplatingwith Nickel4B 374 Terminology Relating to Electroplating4B 487 Test Method for Measurement of Me
13、tal and OxideCoating Thicknesses by Microscopical Examination of aCross Section4B 499 Test Method for Measurement of Coating Thick-nesses by the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis Metals41This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic
14、Coatings and is the direct responsibility of SubcommitteeB08.08.04on Soft Metals.Current edition approved Feb. 10, 2003. Published May 2003. Originallyapproved in 1986. Last previous edition approved in 1998 as B 766 86 (1998).2Discontinued; see 1987 Annual Book of ASTM Standards, Vol 02.05. Replace
15、dby Specification B 766.3Annual Book of ASTM Standards, Vol 03.02.4Annual Book of ASTM Standards, Vol 02.05.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.B 504 Test Method for Measurement of Thickness of Me-tallic Coatings by the C
16、oulometric Method4B 507 Practice for Design of Articles to Be Electroplated onRacks4B 558 Practice for Preparation of Nickel Alloys for Electro-plating4B 567 Test Method for Measurement of Coating Thicknessby the Beta Backscatter Method4B 568 Test Method for Measurement of Coating Thicknessby X-Ray
17、Spectrometry4B 571 Practice for Qualitative Adhesion Testing of MetallicCoatings4B 602 Test Method for Attribute Sampling of Metallic andInorganic Coatings4B 697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic Coatings4E 8 Test Methods for Tension Testi
18、ng of Metallic Materials5F 519 Method for Mechanical Hydrogen EmbrittlementEvaluation of Plating Processes and Service Environments62.3 Federal Standard:QQ-P-416 Plating, Cadmium (Electrodeposited)72.4 International Standard:ISO 2082 Metallic CoatingsElectroplated Coatings ofCadmium on Iron or Steel
19、82.5 Military Standard:MIL-STD-1312 Fasteners, Test Methods93. Terminology3.1 DefinitionsDefinitions of terms used in this specifica-tion are in accordance with Terminology B 374.4. Classification4.1 ClassesElectrodeposited cadmium coatings shall beclassified on the basis of thickness as follows:Cla
20、ss 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 IAs electrodeposited without supplementarytreatment.4.
21、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 In order to make the application of this specificationc
22、omplete, 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).5.1.3 Composition and metallurgical condition of the sub-
23、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 required (6.6).5.1.7 Hydrogen embrittlement relief, if requir
24、ed (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 Configuration, procedures, and tensile load for hy-drogen embrittl
25、ement 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 be essentiallypure cadmium produced by electrodepositi
26、on 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 purchaser.6.3 Stress ReliefSteel parts having an ultimate te
27、nsilestrength 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 for5hormore for stress relief before cleaning and coating.6.4 Preparatory ProceduresThe basis metal shall be sub-jected to such cleanin
28、g 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 embrittlement. If necessary, cleaningmaterials for steel
29、 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 343 and B 558.6.5 SubstrateCadmium shall be deposited direc
30、tly 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 layer shall be5Annual Book of ASTM Standards, Vol 03.01.6Ann
31、ual Book of ASTM Standards, Vol 15.03.7Available from U.S. Government Printing Office, Washington DC 20402.8Available from American National Standards Institute, 25 W. 43rd St., 4thFloor, New York, NY 10036.9Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Phi
32、ladelphia, PA 19111-5094, Attn: NPODS.B 766 86 (2003)2removed and replaced by a metallic zinc layer in accordancewith Guide B 253. For better adherence, a copper strike or anickel coating may be applied to the zinc layer beforeelectroplating with the cadmium.6.6 Plating ProcessThe plating shall be a
33、pplied after allbasis metal 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
34、 190 6 15C for8hormore within 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
35、 be done before the application 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 h
36、ydrogen embrittlement relief.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 solutio
37、n containssulfuric acid, then 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 par
38、ts ofwater. Duration of immersion 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 Type
39、s II and III shall be donein 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 produ
40、ce chromatecoatings. When proprietary 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 t
41、o a desired color.When necessary, 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 reje
42、ction.Presence of clear Type 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 s
43、pray requirements. Waxes and thelike, may be used to improve lubricity.7. 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 normall
44、y visible (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 in
45、dicated 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
46、 fasteners 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 electro
47、de-posited 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 inher
48、ent in 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 v
49、alue; 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 minimu
