1、Designation: B 841 99 (Reapproved 2004)Standard Specification forElectrodeposited Coatings of Zinc Nickel Alloy Deposits1This standard is issued under the fixed designation B 841; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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.1. Scope1.1 This specification covers the requirements for electrode-posited zinc nickel alloy coatings on metals.1.2 Th
3、e values stated in SI units are to be regarded as thestandard.1.3 The following precautionary statement pertains to thetest method portion only, Section 8, of this specification: Thisstandard does not purport to address all of the safety concerns,if any, associated with its use. It is the responsibi
4、lity of the userof this standard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB 183 Practice for Preparation of Low-Carbon S
5、teel forElectroplatingB 242 Guide for Preparation of High-Carbon Steel ForElectroplatingB 320 Practice for Preparation of Iron Castings for Electro-platingB 322 Guide for Cleaning Metals Prior to ElectroplatingB 374 Terminology Relating to ElectroplatingB 487 Test Method for Measurement of Metal and
6、 OxideCoating Thickness by Microscopical Examination of aCross SectionB 499 Test Method for Measurement of Coating Thick-nesses By the Magnetic Method: Nonmagnetic Coatingson Magnetic Basis MetalsB 504 Test Method for Measurement of Thickness of Me-tallic Coatings by the Coulometric MethodB 507 Prac
7、tice for Design of Articles To Be Electroplatedon RacksB 568 Test Method 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
8、Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB 762 Test Method of Variables Sampling of Metallic andInorganic CoatingsB 849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen EmbrittlementB 850 Guide for Post-Coating Treatments of Steel
9、for Re-ducing the Risk of Hydrogen EmbrittlementB 3951 Practice for Commercial Packaging3. Terminology3.1 DefinitionsMany items used in this specification aredefined in Terminology B 374.3.2 Definitions of Terms Specific to This Standard:3.2.1 significant surface, nthat portion of a coated arti-cles
10、 surface where the coating is required to meet all therequirements of the coating specification for that article.Significant surfaces are usually those that are essential to theserviceability or function of the article, or that can be a sourceof corrosion products or tarnish films that interfere wit
11、h thefunction or desirable appearance of the article.3.2.2 DiscussionSignificant surfaces are those surfacesthat are identified by the purchaser by, for example, indicatingthem on an engineering drawing of the product or marking asample item of the product.4. Classification4.1 There is one class of
12、zinc nickel coating defined asfollows:4.1.1 Class 1Deposits having a minimum of 5 and maxi-mum 12 mass % nickel, the balance being zinc.4.2 There are five chromate conversion coating types thatare defined as follows:4.2.1 Type AWith colorless (blue bright) conversion coat-ings,4.2.2 Type BWith yello
13、w iridescent conversion coatings,4.2.3 Type CWith bronze conversion coatings,1This specification is 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, 2004. Published
14、 August 2004. Originallyapproved in 1993. Last previous edition approved in 1999 as B 841 99.2For 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
15、Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2.4 Type DWith black chromate conversion coatings,and4.2.5 Type EAny of the above plus organic topcoat.NOTE 1Whereas colored chromate conversion coatin
16、gs are usuallymeant to include various shades of yellow to bronze when used withnonalloyed zinc, yellow and bronze chromate conversion coatings areconsidered distinctly different in appearance and performance whenapplied to alloyed zinc coatings and are formulated specifically to producethe desired
17、coating and are formulated specifically to produce the desiredcoating.4.3 There are three grades according to thickness and aredefined as follows:Minimum Thickness, m New ASTM Grade Old ASTM Grade55188210 10 35. Ordering Information5.1 In order to make the application of this specificationcomplete,
18、the purchaser needs to supply the following infor-mation to the seller in the purchase order and drawings:5.1.1 Title, ASTM designation number, and date of issue ofthis standard specification,5.1.2 Deposit by classification including Class, Type, andGrade (see 4.1, 4.2, 4.3),5.1.3 Composition and me
19、tallurgical condition of the sub-strate to be coated,5.1.4 Location of significant surfaces (see 3.2.1),5.1.5 Heat treatment for stress relief, whether it has beenperformed by purchaser or is required (see 6.7),5.1.6 Heat treatment after electroplating, if required (see6.8),5.1.7 Whether or not loca
20、tion of rack marks is to be defined(see 6.3.1),5.1.8 Any requirement for special test specimens (see8.1.1),5.1.9 Acceptance inspection procedure to be used (seeSection 8), and5.1.10 Any requirement for certification (see Section 10).5.1.11 Any other items needing agreement. For the purposesof this s
21、pecification, prior agreement on the nature of the finishis required as items plated in bulk may differ in appearancefrom those that are rack plated.6. Coating Requirements6.1 SubstrateThe metal to be plated shall be free of flawsand defects that will be detrimental to the zinc alloy coating. Itshal
22、l be subjected to such cleaning, pickling, and electroplatingprocedures as are necessary to yield deposits with the desiredquality.NOTE 2Proper preparatory procedures and thorough cleaning areessential to ensure satisfactory adhesion and corrosion resistance perfor-mance of the coating. Materials us
23、ed for cleaning should not damage thebasis metal, for example by causing defects such as pits, intergranularattack or stress corrosion cracking. It is recommended that the followingpractices for cleaning, where appropriate, be used: Practices B 183 andB 320, and Guides B 242 and B 322.6.1.1 The elec
24、troplating shall be applied after all basis metalheat treatments have been completed.6.2 Nature of Coating:6.2.1 The coating shall consist of a zinc nickel alloy that hasa minimum of 5 and maximum 12 mass percent nickel, thebalance being zinc.6.2.2 The coating shall be produced from an aqueouselectr
25、oplating system that may be either an alkaline or acidformulation as specified by the purchaser.6.2.3 The coating shall have such supplementary conversioncoatings as defined in 4.2 and specified in the purchase order.6.3 Appearance:6.3.1 The coating on all ready visible surfaces shall have anaccepta
26、ble and characteristic appearance as agreed upon by thepurchaser and seller. The coating shall be uniform insofar asthe basis metal will permit. When the article is to be plated ona rack, contact marks may be unavoidable. Location of suchmarks(s) shall be indicated on the article or its drawing.6.3.
27、2 Defects and variations in appearance that arise fromsurface conditions of the substrate (scratches, pores, roll marks,inclusions, and the like) and that persist in the coating despitethe observance of good metal finishing practices shall not because for rejection. The coating shall be adherent, fr
28、ee fromblisters, pits, or discontinuities, and shall be free of cracks inthe as plated state. Flaking shall be cause for rejection in eitherthe as plated state or after subsequent operations.NOTE 3These coatings are commonly used in automotive applica-tions where subsequent forming, bending, and cri
29、mping operations arecommonly performed. These operations will necessarily detract from theperformance of the coatings. While some cracking of coatings will beunavoidable, flaking of the coating after these subsequent operations shallbe cause for rejection.NOTE 4Coatings generally perform better in s
30、ervice when the sub-strate over which they are applied is smooth and free of torn metal,inclusions, pores, and other defects. The specifications covering theunfinished product should provide limits for these defects.Ametal finishercan often remove defects through special treatments, such as grinding
31、polishing, abrasive blasting, chemical etches, and electropolishing. How-ever, these are not normal in the treatment steps preceding the applicationof the coating. When they are desired, they are the subject of specialagreement between the purchaser and the seller.6.4 Thickness:6.4.1 The thickness
32、of the coating everywhere on thesignificant surfaces as defined in 3.2.1 and shall conform to therequirements of the specified grade as defined in 4.3.NOTE 5The thickness of electrodeposited coatings varies from pointto point on the surfaces of a product (see Practice B 507). The thicknessis less in
33、 interior corners and in holes. Such surfaces are often exemptfrom thickness requirements. If the full thickness is required in thoselocations, the electroplater will have to use special techniques that willprobably raise the cost of the process.NOTE 6The coating requirement of this specification is
34、 a minimum.Variation in the thickness from point to point on an article and from articleto article in a production lot is inherent in electroplating. Therefore, if allof the articles in a production lot are to meet the thickness requirement, theaverage coating thickness for the production lot as a w
35、hole will be greaterthan the specified minimum.6.5 AdhesionThe coating shall withstand normal handlingand storage conditions without chipping, flaking, or othercoating damage and shall conform to the minimum require-ments set forth in Section 8.B 841 99 (2004)26.6 CorrosionThe corrosion resistance o
36、f the coating maybe evaluated using the method in Appendix X1.6.7 Pretreatment of Iron and Steel for Reducing the Risk ofHydrogen Embrittlement:6.7.1 Parts that are made of steels with ultimate tensilestrengths of 1000 MPa (hardness of 31 HRC or greater) thathave been machined, ground, cold formed,
37、or cold straightenedsubsequent to heat treatment shall require stress relief heattreatment when specified by the purchaser, the tensile strengthto be supplied by the purchaser. Specification B 849 may beconsulted for a list of pre-treatments that are widely used.6.8 Post-Coating Treatments of Iron a
38、nd Steel for Reducingthe Risk of Hydrogen Embrittlement:6.8.1 Parts that are made of steels with ultimate tensilestrengths of 1000 MPa (hardness of 31 HRC or greater), aswell as surface hardened parts, may require post-coatinghydrogen embrittlement relief baking when specified by thepurchaser, the t
39、ensile strength to be supplied by the purchaser.Specification B 850 may be consulted for a list of post-treatments that are widely used.7. Sampling7.1 The sampling plan used for the inspection of a quantityof the coated articles shall be as agreed upon between thepurchaser and the seller.NOTE 7Usual
40、ly, when a collection of coated articles, the inspectionlot (see 7.2), is examined for compliance with the requirements placed onthe articles, a relatively small number of the articles, the sample, isselected at random and is inspected. The inspection lot is then classified ascomplying or not comply
41、ing with the requirements based on the results ofthe inspection of the sample. The size of the sample and the criteria ofcompliance are determined by the application of statistics. The procedureis known as sampling inspection. Three standards, Test Method B 602,Guide B 697, and Test Method B 762 con
42、tain sampling plans that aredesigned for the sampling inspection of coatings. Test Method B 602contains four sampling plans, three for use with tests that are nondestruc-tive and one when they are destructive. The buyer and seller may agree onthe plan or plans to be used. If they do not, Test Method
43、 B 602 identifiesthe plan to be used. Guide B 697 provides a large number of plans and alsogives guidance in the selection of a plan. When Guide B 697 is specified,the buyer and seller need to agree on the plan to be used. Test MethodB 762 can be used only for coating requirements that have a numeri
44、callimit, such as a coating thickness. The test must yield a numerical valueand certain statistical requirements must be met. Test Method B 762contains several plans and also gives instructions for calculating plans tomeet special needs. The buyer and the seller may agree on the plan orplans to be u
45、sed. If they do not, Test Method B 762 identifies the plan tobe used.NOTE 8When both destructive and nondestructive tests exist for themeasurement of a characteristic, the purchaser needs to state which is tobe used so that the proper sampling plan is selected.Atest may destroy thecoating but in a n
46、oncritical area; or, although it may destroy the coating,a tested part can be reclaimed by stripping and recoating. The purchaserneeds to state whether the test is to be considered destructive ornondestructive.7.2 An inspection lot shall be defined as a collection ofcoated articles that are of the s
47、ame kind, that have beenproduced to the same specification that have been coated by asingle supplier at one time or at approximately the same timeunder essentially identical conditions, and that are submittedfor acceptance or rejection as a group.7.3 If special test specimens are used to represent t
48、he coatedarticles in a test, the number used shall be that required in 8.1.1.8. Test Methods8.1 Special Test Specimens:8.1.1 The permission or the requirement to use special testspecimens, the number to be used, the material from whichthey are to be made, and their shape and size shall be stated byt
49、he purchaser.NOTE 9Test specimens often are used to represent the coated articlesin a test if the articles are of a size, shape, or material that is not suitablefor the test or if it is preferred not to submit articles to a destructive testbecause, for example, the articles are expensive or few in number. Thespecimen should duplicate the characteristics of the article that influencethe property being tested.8.1.2 Special test specimens used to represent articles in anadhesion, porosity, corrosion resistance, or appearance testshall be made of the same material,
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