1、Designation: F 1941 07Standard Specification forElectrodeposited Coatings on Threaded Fasteners (UnifiedInch Screw Threads (UN/UNR)1This standard is issued under the fixed designation F 1941; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, the 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.INTRODUCTIONThis specification covers the coating of steel unified inch screw threaded fasteners by electrod
3、epo-sition. The properties of the coatings shall conform to the ASTM standards for the individual finisheslisted.Coating thickness values are based on the tolerances for 1A and 2A external Unified Inch ScrewThreads. The coating must not cause the basic thread size to be transgressed by either the in
4、ternal orexternal threads. The method of designating coated threads shall comply with ASME B1.1.With normal methods for depositing metallic coatings from aqueous solutions, there is a risk ofdelayed failure due to hydrogen embrittlement for case hardened fasteners and fasteners having ahardness 40 H
5、RC or above. Although this risk can be managed by selecting raw materials suitable forthe application of electrodeposited coatings and by using modern methods of surface treatment andpost heat-treatment (baking), the risk of hydrogen embrittlement cannot be completely eliminated.Therefore, the appli
6、cation of a metallic coating by electrodeposition is not recommended for suchfasteners.1. Scope*1.1 This specification covers application, performance anddimensional requirements for electrodeposited coatings onthreaded fasteners with unified inch screw threads. It specifiescoating thickness, supple
7、mentary hexavalent chromate or triva-lent chromite finishes, corrosion resistance, precautions formanaging the risk of hydrogen embrittlement and hydrogenembrittlement relief for high-strength and surface-hardenedfasteners. It also highlights the differences between barrel andrack plating and makes
8、recommendations as to the applicabilityof each process.1.2 The values 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 precautionar
9、y statement pertains to thetest method portion only, Section 9, of this 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 det
10、ermine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB 487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination of CrossSectionB 499 Test Method for Me
11、asurement 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 MethodB 567 Test Method for Measurement of Coating Thicknessby the Beta Backscatter MethodB 568 Test Method fo
12、r Measurement of Coating Thicknessby X-Ray SpectrometryB 659 Guide for Measuring Thickness of Metallic andInorganic Coatings1This specification is under the jurisdiction of ASTM Committee F16 onFasteners and is the direct responsibility of Subcommittee F16.03 on Coatings onFasteners.Current edition
13、approved Dec. 1, 2007. Published January 2008. Originallyapproved in 1998. Last previous edition approved in 2006 as F 1941 00 (2006).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume info
14、rmation, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D 6492 Practice for Detection of Hexavalent Ch
15、romium OnZinc and Zinc/Aluminum Alloy Coated SteelE 376 Practice for Measuring Coating Thickness byMagnetic-Field or Eddy-Current (Electromagnetic) Exami-nation MethodsF 606 Test Methods for Determining the Mechanical Prop-erties of Externally and Internally Threaded Fasteners,Washers, Direct Tensio
16、n Indicators, and RivetsF 1470 Guide for Fastener Sampling for Specified Mechani-cal Properties and Performance InspectionF 1624 Test Method for Measurement of Hydrogen Em-brittlement Threshold in Steel by the Incremental StepLoading TechniqueF 1940 Test Method for Process Control Verification toPre
17、vent Hydrogen Embrittlement in Plated or CoatedFasteners2.2 ASME Standard:3B1.1 Unified Inch Screw Threads (UN and UNR ThreadForm)2.3 National Aerospace Standard (AIA):4NASM-1312-5 Fast Test Method - Method 5: Stress Dura-bility2.4 IFI Standard:5IFI-142 Hydrogen Embrittlement Risk Management3. Termi
18、nology3.1 Definitions:3.1.1 local thicknessthe mean of the thickness measure-ments, of which a specified number is made within a referencearea.3.1.2 minimum local thicknessthe lowest local thicknessvalue on the significant surface of a single article.3.1.3 reference areathe area within which a speci
19、fiednumber of single measurements are required to be made.3.1.4 significant surfacesignificant surfaces are areaswhere the minimum thickness to be met shall be designated onthe applicable drawing or by the provision of a suitably markedsample. However, if not designated, significant surfaces shallbe
20、 defined as those normally visible, directly or by reflection,which are essential to the appearance or serviceability of thefastener when assembled in normal position, or which can bethe source of corrosion products that deface visible surfaces onthe assembled fastener. Figs. 1 and 2 illustrate sign
21、ificantsurfaces on standard externally threaded and internallythreaded fasteners.4. Classification4.1 Coating Material The coating material shall be se-lected and designated in accordance with Table 1.4.2 Coating ThicknessThe coating thickness shall beselected and designated in accordance with Table
22、 2:4.3 Chromate FinishWhen not specified, the hexavalentor trivalent chromiate finish shall be used at the option of themanufacturer and its appearance shall be selected in accor-dance with the designation selected in Table 3.4.3.1 Trivalent Chromite FinishUnless otherwise speci-fied, the typical ap
23、pearance of the trivalent chromite finishshall be transparent, colorless and shall not be subjected to therequirements of typical appearance as determined in Table 3.Inaddition, the classification code to be used shall be appendedwith the letter 9T9 (for example, Fe/Zn 5CT, as defined in TableA1.1 )
24、.5. Ordering Information for Electroplating5.1 When ordering threaded fasteners to be coated byelectrodeposition in accordance with this specification, thefollowing information shall be supplied to the electroplater:5.1.1 The desired coating, coating thickness, the chromatefinish, the color and appe
25、arance (if applicable), or the classi-fication codes as specified in Tables 1-3. (for example, Fe/Zn5C denotes yellow zinc plated with a minimum thickness of0.0002 in. on significant surfaces.)5.1.2 The identification of significant surfaces (optional).5.1.3 The requirement, if any, for stress relie
26、f before elec-troplating, in which case the stress-relief conditions must bespecified.5.1.4 The requirements, if any, for hydrogen embrittlementrelief by heat treatment (baking) stating the tensile strength orsurface hardness of the fasteners and/or baking time andtemperature.NOTE 1Fasteners with a
27、specified maximum hardness of 34 HRC andbelow have a very low susceptibility to hydrogen embrittlement and donot require baking.3Available from American Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Three Park Ave., New York, NY 10016-5990, http:/www.asme.org.4Available fro
28、m Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098.5Available from Industrial Fasteners Institute (IFI), 1717 East 9th Street, Suite1105, Cleveland, OH 441142879.NOTE 1Black dot () indicates test surface.FIG. 1 Significant Surfaces on Ext
29、ernally Threaded FastenersNOTE 1Black dot () indicates test surface.FIG. 2 Significant Surfaces on Internally Threaded FastenersF19410725.1.5 The requirements, if any, for the type of electroplatingprocess (barrel-plating or rack-plating). See Section 10 andAppendix X1.5.1.6 The designation of coate
30、d thread class shall complywith ASME B1.1.6. Requirements6.1 Coating RequirementsThe electrodeposited coating asordered shall cover all surfaces and shall meet the followingrequirements:6.1.1 The coating metal deposit shall be bright or semi-bright unless otherwise specified by the purchaser, smooth
31、, finegrained, adherent and uniform in appearance.6.1.2 The coating shall be free of blisters, pits, nodules,roughness, cracks, unplated areas, and other defects that willaffect the function of the coating.6.1.3 The coating shall not be stained, discolored or exhibitany evidence of white or red corr
32、osion products.6.1.3.1 Slight discoloration that results from baking, drying,or electrode contact during rack-plating, or all of these, as wellas slight staining that results from rinsing shall not be cause forrejection.6.2 Corrosion ResistanceCoated fasteners, when testedby continuous exposure to n
33、eutral salt spray in accordance with9.3, shall show neither corrosion products of coatings (whitecorrosion) nor basis metal corrosion products (red rust) at theend of the test period. The appearance of corrosion productsvisible to the unaided eye at normal reading distance shall because for rejectio
34、n, except when present at the edges of thetested fasteners. Refer to Annex A1 for neutral salt sprayperformance requirements for zinc, zinc alloy and cadmiumcoatings.6.3 ThicknessThe coating thickness shall comply withrequirements of Table 2 when measured in accordance with9.1.6.3.1 Restrictions on
35、Coating ThicknessThis specificationimposes minimum local thickness requirements at significantsurfaces in accordance with Table 2. Thick or thin localthickness in a location other than a significant surface shall notbe a cause for rejection. However the following restrictionsapply:6.3.1.1 Minimum co
36、ating thickness at low current densityareas, such as the center of a bolt or recesses, must be sufficientto provide for adequate chromate adhesion.6.3.1.2 External Threads Maximum coating thickness athigh current density threaded tips must provide for class 3AGO thread gauge acceptance.6.3.1.3 Inter
37、nal Threads Maximum coating thickness ofinternal threads must provide for class 1B, 2B, or 3B Go threadgage acceptance.6.3.1.4 Surfaces such as threads, holes, deep recesses, basesof angles, and similar areas on which the specified thickness ofdeposit cannot readily be controlled, are exempted fromm
38、inimum thickness requirements unless they are speciallydesignated as not being exempted. When such areas are subjectto minimum thickness requirements, the purchaser and themanufacturer shall recognize the necessity for either thickerdeposits on other areas or special racking.6.3.2 Applicability to U
39、nified Inch Screw Threads:6.3.2.1 The applicability of the required coating to unifiedinch screw threads is limited by the basic deviation of thethreads, and hence limited by the pitch diameter, allowance andtolerance positions. Refer to Appendix X3 as a guideline forthe tolerances of the various th
40、read sizes and classes and thecoating thickness they will accommodate.6.3.2.2 Because of the inherent variability in coating thick-ness by the barrel-plating process, the application of a mini-mum coating thickness of 0.0005 in. is not recommended for astandard screw thread by this method due to the
41、 fact thatdimensional allowance of most threaded fasteners normallydoes not permit it. If the size of the fastener is large enough toeconomically use the rack-plating process, then the latter shallbe used to obtain this thickness requirement. If heaviercoatings are required allowance for the deposit
42、 buildup must bemade during the manufacture of fasteners.6.3.3 Applicability to Wood Screws and Thread FormingScrewsAny classification code in Table 2 may be applied toscrews that cut or form their own threads.6.4 Hydrogen Embrittlement Relief:6.4.1 Requirement for BakingCoated fasteners made fromst
43、eel heat treated to a specified hardness of 40 HRC or above,TABLE 1 Designation of Common Coating MaterialsCoating Designation Coating TypeFe/Zn ZincFe/Cd CadmiumFe/Zn-Co Zinc Cobalt AlloyFe/Zn-Ni Zinc Nickel AlloyFe/Zn-Fe Zinc Iron AlloyTABLE 2 Designation of Coating ThicknessNOTE 1The conversion f
44、actor from inch to microns is 2.54 3 104(forexample, 0.0001 in. = 2.54 m).Thickness Designation Minimum Thickness in.3 0.00015 0.00028 0.000312 0.0005TABLE 3 Designation of Chromate FinishNOTE 1Coated fasteners with trivalent chromite (Cr+3) are notsubjected to the required yellow, opaque, and black
45、 color. See AppendixX5NOTE 2When fasteners are coated with trivalent chromite (Cr+3) theclassification code to be used shall be appended with the letter 9T9 .Designation Type Typical AppearanceA Clear Transparent colorless with slight iridescenceB Blue-bright Transparent with a bluish tinge and slig
46、ht irides-cenceC Yellow Yellow iridescentD Opaque Olive green, shading to brown or bronzeE Black Black with slight iridescenceF Organic Any of the above plus organic topcoatF1941073case-hardened steel fasteners, and fasteners with captive wash-ers made from hardened steel shall be baked to minimize
47、therisk of hydrogen embrittlement. Unless otherwise specified bythe purchaser, baking is not mandatory for fasteners withspecified maximum hardness below 40 HRC.NOTE 2With proper care many steel fasteners can be plated withoutbaking by correlating process conditions to the susceptibility of thefaste
48、ner material to hydrogen embrittlement, and by applying adequateprocess control procedures, such as those outlined in Appendix X4.2. TestMethod F 1940 is a recognized verification method for process control tominimize the risk of hydrogen embrittlement. Upon agreement betweenthe supplier and the pur
49、chaser, this test method can be used as a basis fordetermining if baking should be mandated in a controlled processenvironment.6.4.2 Baking ConditionsAt the time of publication of thisspecification it was not considered possible to give an exactbaking duration. Eight hours is considered a typical example ofbaking duration. However, upon agreement between the pur-chaser and the manufacturer, baking times between 2 and 24 hat temperatures of 350 to 450F are suitable depending on thetype and size of the fastener, geometry, mechanical properties,cleaning pr
