1、Designation: B 842 99 (Reapproved 2005)Standard Specification forElectrodeposited Coatings of Zinc Iron Alloy Deposits1This standard is issued under the fixed designation B 842; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear 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 iron alloy coatings on metals.1.2 The va
3、lues stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 The following precautionary caveat pertains to the testmethod portion only, Section 8, of t
4、his specification: Thisstandard does not purport to address all of the safety concerns,if any, associated with its use. It is the responsibility of the userof this standard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2.
5、Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB 183 Practice for Preparation of Low-Carbon Steel forElectroplatingB 242 Guide for Preparation of High-Carbon Steel forElectroplatingB 320 Practice for Preparation of Iron Castings for Electro-platingB 322
6、 Guide for Cleaning Metals Prior to ElectroplatingB 374 Terminology Relating to ElectroplatingB 487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination of aCross SectionB 499 Test Method for Measurement of Coating Thick-nesses by the Magnetic Method: Nonmagne
7、tic Coatings onMagnetic Basis MetalsB 504 Test Method for Measurement of Thickness of Me-tallic Coatings by the Coulometric MethodB 568 Test Method for Measurement of Coating Thicknessby X-Ray SpectrometryB 571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB 602 Test Method for Attrib
8、ute Sampling of Metallic andInorganic CoatingsB 697 Guide for Selection of 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
9、 of Hydrogen EmbrittlementB 850 Guide for Post-Coating Treatments of Steel for Re-ducing the Risk of Hydrogen EmbrittlementD 3951 Practice for Commercial Packaging3. Terminology3.1 DefinitionsMany terms used in this specification aredefined in Terminology B 374.3.2 Definitions of Terms Specific to T
10、his Standard:3.2.1 significant surface, nthat portion of a coated arti-cles surface where the coating is required to meet all therequirements of the coating specification for that article.3.2.1.1 DiscussionSignificant surfaces are usually thosethat are essential to the serviceability or function of
11、the article,or that can be a source of corrosion products or tarnish filmsthat interfere with the function or desirable appearance of thearticle. Significant surfaces are those surfaces that are identi-fied by the purchaser by, for example, indicating them on anengineering drawing of the product or
12、marking a sample itemof the product.4. Classification4.1 There is one class of zinc iron alloy that is defined asfollows:4.1.1 Class 1Deposits having approximately 99 mass %zinc, balance iron.4.2 There are two coating types that are defined as follows:4.2.1 Type AZinc iron with black chromate conver
13、sioncoating, and1This 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 Oct. 15, 2005. Published October 2005. Originallyapproved in 1993. Last previous edi
14、tion approved in 1999 as B 842 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 Summary page onthe ASTM website.1Copyright ASTM Internation
15、al, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2.2 Type BZinc iron with iridescent yellow chromateconversion coating.4.3 There are three coating grades according to thicknessthat are defined as follows:Minimum Thickness, m New ASTM Grade Old ASTM Grade66112
16、 12 218 18 35. Ordering Information5.1 In order to make the application of this specificationcomplete, 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 specification,5.1.2 Deposit
17、by classification including class (see 4.1),type (see 4.2), and grade (see 4.3),5.1.3 Composition and metallurgical condition of the sub-strate to be coated,5.1.4 Location of significant surfaces (see 3.2),5.1.5 Heat treatment for stress relief, whether it has beenperformed by purchaser or is requir
18、ed (see 6.7),5.1.6 Heat treatment after electroplating, if required (see6.8),5.1.7 Any requirement for submission of sample coatedarticles,5.1.8 Whether or not location of rack marks is to be defined(see 6.3.1),5.1.9 Any requirement for special test specimens (see 8.1),5.1.10 Acceptance inspection p
19、rocedure to be used (seeSection 8),5.1.11 Any requirement for certification (see Section 10),and5.1.12 Any other items needing agreement. For the purposesof this specification, prior agreement on the nature of the finishis required as items plated in bulk may differ slightly inappearance from those
20、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. Itshall be subjected to such cleaning, pickling, and electroplatingprocedures as are necessary to yield deposits with the desiredquali
21、ty.NOTE 1Proper preparatory procedures and thorough cleaning areessential to ensure satisfactory adhesion and corrosion resistance perfor-mance of the coating. Materials used for cleaning should not damage thebasis metal. It is recommended that the following practices for cleaning beused, where appr
22、opriate: Practices B 183 and B 320, and Guides B 242and B 322.6.1.1 The electroplating shall be applied after all basis metalheat treatments have been completed.6.2 Nature of CoatingThe coating shall consist of a zinciron alloy that is approximately 99 mass % zinc and the balanceiron.6.3 Appearance:
23、6.3.1 The coating on all readily visible surfaces shall havean acceptable and characteristic appearance as agreed upon bythe purchaser and seller. The coating shall be uniform insofaras the basis metal will permit. When the article is to be platedon a rack, contact marks may be unavoidable. Location
24、 of suchmarks(s) shall be indicated on the article or its drawing.6.3.2 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 practi
25、ces shall not because for rejection. The coating shall be adherent, free 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 2These coatings are commonly used
26、in automotive applica-tions where subsequent forming, bending, and crimping 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 sh
27、allbe cause for rejection.NOTE 3Coatings generally perform better in service 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 finishe
28、rcan often remove defects through special treatments, such as grinding,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 b
29、etween the purchaser and the seller.6.4 ThicknessThe thickness of the coating everywhere onthe significant surfaces shall conform to the requirements asspecified in 4.2 and defined in 3.2.1.NOTE 4The coating requirement of this specification is a minimum.Variation in the thickness from point to poin
30、t 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 whole will be greaterthan the specified minimum.6.5 Adhes
31、ionThe 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 8.6.6 Corrosion ResistanceThe corrosion resistance of thecoating may be evaluated using the method in Appendix X1
32、.6.7 Pretreatment of Iron and Steel to Reduce 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, or cold straightenedsubsequent to heat treatment shall require s
33、tress relief heattreatment when specified by the purchaser, the tensile strengthto be supplied by the purchaser. Specification B 849 may beconsulted for a list of pretreatments that are widely used.6.8 Coating Treatments of Iron and Steel to Reduce the Riskof Hydrogen Embrittlement:6.8.1 Parts that
34、are made of steels with ultimate tensilestrengths of 1000 MPa (hardness of 31 HRC or greater) as wellas surface hardened parts, may require post-coating hydrogenembrittlement relief baking when specified by the purchaser,the tensile strength to be supplied by the purchaser. GuideB 850 may be consult
35、ed for a list of post-treatments that arewidely used.B 842 99 (2005)27. 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 5Usually, when a collection of coated articles, the inspectionlot (see 7.
36、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 complying with the requirements based on the results ofthe inspection of
37、the sample. The size of the sample and the criteria forcompliance are determined by the application of statistics. This procedureis known as sampling inspection. Three standards, Test Method B 602,Guide B 697, and Test Method B 762, contain sampling plans that aredesigned for the sampling inspection
38、 of coatings. Test Method B 602contains four sampling plans, three for use with tests that are nondestruc-tive and one for destructive tests. The buyer and seller may agree on theplan or plans to be used. If they do not, Test Method B 602 identifies theplan to be used. Guide B 697 provides a large n
39、umber 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 numericallimit, such as a coating thickness. The test must yield a numeric
40、al 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 used. If they do not, Test Method B 762 identifies the plan tobe used
41、.NOTE 6When 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 noncritical area, or, although it may destroy the coating,a tested pa
42、rt 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 same kind, that have beenproduced to the same specification, that hav
43、e 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 the coatedarticles in a test, the number used shall be that required
44、 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 the shape and size of the specimens,shall be stated by the purchaser.NOTE 7Test specimens often are used to
45、 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 characteri
46、stics 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, in the same metallurgicalcondition, and have the same surface condition as the art
47、iclesthey represent, and be placed in the production lot of and beprocessed along with the articles they represent.8.1.3 Special test specimens used to represent articles in acoating thickness test may be made of a material that is suitablefor the test method even if the represented article is not o
48、f thesame material. For example, a low-carbon steel specimen mayrepresent a brass article when the magnetic thickness test isused (see Test Method B 499). The thickness specimen neednot be carried through the complete process with the repre-sented article. If not, introduce it into the process at th
49、e pointwhere the coating is applied and carry it through all steps thathave a bearing on the coating thickness. In rack plating, rackthe specimen in the same way with the same distance from andorientation with the anodes and other items in the process asthe article it represents.NOTE 8When special test specimens are used to represent coatedarticles in a thickness test, the specimens will not necessarily have thesame thickness and thickness distribution as the articles unless thespecimens and the articles are of the same general size and shape.Therefore, before fi
