1、Designation: F1941 10Standard Specification forElectrodeposited Coatings on Threaded Fasteners (UnifiedInch Screw Threads (UN/UNR)1This standard is issued under the fixed designation F1941; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONThis specification covers the coating of steel unified inch screw threaded fasteners by electrodepo
3、-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 inter
4、nal 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 HRC
5、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 applicat
6、ion 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, supplemen
7、tary hexavalent chromate or non-hexavalent passivate finishes, corrosion resistance, precautionsfor managing the risk of hydrogen embrittlement and hydrogenembrittlement relief for high-strength and surface-hardenedfasteners. It also highlights the differences between barrel andrack plating and make
8、s recommendations as to the applicabilityof each process.1.2 The values stated in inch-pound units are to be regardedas standard. No other units of measurement are included in thisstandard.1.3 The following precautionary statement pertains to thetest method portion only, Section 9, of this specifica
9、tion: 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. Referenced Do
10、cuments2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination of CrossSectionB499 Test Method for Measurement of Coating Thick-nesses by the Magnetic Method: Nonmagnetic Coatings onMa
11、gnetic Basis MetalsB504 Test Method for Measurement of Thickness of Me-tallic Coatings by the Coulometric MethodB567 Test Method for Measurement of Coating Thicknessby the Beta Backscatter MethodB568 Test Method for Measurement of Coating Thicknessby X-Ray SpectrometryB659 Guide for Measuring Thickn
12、ess of Metallic and Inor-ganic CoatingsD6492 Practice for Detection of Hexavalent Chromium OnZinc and Zinc/Aluminum Alloy Coated SteelE376 Practice for Measuring Coating Thickness byMagnetic-Field or Eddy-Current (Electromagnetic) Exami-nation Methods1This specification is under the jurisdiction of
13、ASTM Committee F16 onFasteners and is the direct responsibility of Subcommittee F16.03 on Coatings onFasteners.Current edition approved Dec. 15, 2010. Published January 2011. Originallyapproved in 1998. Last previous edition approved in 2007 as F1941 07. DOI:10.1520/F1941-10.2For referenced ASTM sta
14、ndards, 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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM Int
15、ernational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.F606 Test Methods for Determining the Mechanical Prop-erties of Externally and Internally Threaded Fasteners,Washers, Direct Tension Indicators, and RivetsF1470 Practice for Fastener Sampling for Specifie
16、d Me-chanical Properties and Performance InspectionF1624 Test Method for Measurement of Hydrogen Em-brittlement Threshold in Steel by the Incremental StepLoading TechniqueF1940 Test Method for Process Control Verification toPrevent Hydrogen Embrittlement in Plated or CoatedFasteners2.2 ASME Standard
17、: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. Terminology3.1 Definitions:3.1.1 local thicknessthe mean of the thickness meas
18、ure-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 specifiednumber of single measurements are required to be made.3.1.4 significa
19、nt 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 defined as those normally visible, directly or by reflection,which are e
20、ssential 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 significantsurfaces on standard externally threaded and internallythreaded fa
21、steners.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 2:4.3 Chromate FinishWhen not specified, the hexavalent,trivalent or oth
22、er chromiate finish shall be used at the option ofthe manufacturer and its appearance shall be selected inaccordance with the designation selected in Table 3.4.3.1 Passivatefor the purpose of this specification, aconversion coating shall not contain hexavalent chromium.4.3.1.1 Trivalent Chromite Pas
23、sivate FinishUnless other-wise specified, the typical appearance of the trivalent chromitefinish shall be transparent, colorless and shall not be subjectedto the requirements of typical appearance as determined inTable 3. In addition, the classification code to be used shall beappended with the lett
24、er 9T9 (for example, Fe/Zn 5CT, asdefined in Table A1.1 ).4.3.1.2 Supplemental Passivate Finish Unless otherwisespecified, the typical appearance of the supplemental passivatefinish shall be transparent, colorless and shall not be subjectedto the requirements of typical appearances as determined inT
25、able 3. In addition, the classification code to be used shall beappended with the letter “S” (for example Fe/Zn 5AS). Othercolored finishes may be specified at time of purchase. Require-ments of the other colored finishes to be agreed upon at time ofpurchase.3Available from American Society of Mecha
26、nical Engineers (ASME), ASMEInternational Headquarters, Three Park Ave., New York, NY 10016-5990, http:/www.asme.org.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098.5Available from Industrial Fasteners Institute (IFI), 17
27、17 East 9th Street, Suite1105, Cleveland, OH 441142879.NOTE 1Black dot () indicates test surface.FIG. 1 Significant Surfaces on Externally Threaded FastenersNOTE 1Black dot () indicates test surface.FIG. 2 Significant Surfaces on Internally Threaded FastenersTABLE 1 Designation of Common Coating Mat
28、erialsCoating 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 factor from inch to microns is 2.54 3 104(forexample, 0.0001 in. = 2.54 m).Thickness Designation Minim
29、um Thickness in.3 0.00015 0.00028 0.000312 0.0005F1941 102NOTE 1The use of supplemental passivated finishes are technicallynot “chromate” films and they do not contain hexavalent chromium ions,they are supplemental coatings that render the active zinc surface passiveand provide protection to the ste
30、el fastener.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 chromateor passivate fi
31、nish, the color and appearance (if applicable), orthe classification codes as specified in Tables 1-3. (for example,Fe/Zn 5C denotes yellow zinc plated with a minimum thick-ness of 0.0002 in. on significant surfaces.)5.1.2 The identification of significant surfaces (optional).5.1.3 The requirement,
32、if any, for stress relief 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
33、.NOTE 2Fasteners with a specified maximum hardness of 34 HRC andbelow have a very low susceptibility to hydrogen embrittlement and donot require baking.5.1.5 The requirements, if any, for the type of electroplatingprocess (barrel-plating or rack-plating). See Section 10 andAppendix X1.5.1.6 The desi
34、gnation of coated 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 p
35、urchaser, smooth, 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 w
36、hite or red corrosion 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 continuo
37、us exposure to neutral 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 beca
38、use for rejection, 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
39、Restrictions on 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.
40、3.1.1 Minimum coating 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 acceptan
41、ce.6.3.1.3 Internal 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, ar
42、e exempted fromminimum 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 Ap
43、plicability to Unified 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 o
44、f the various thread 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 m
45、ethod due to the 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
46、 for the deposit buildup must bemade during the manufacture of fasteners.TABLE 3 Designation of Chromate FinishNOTE 1Coated fasteners with trivalent chromite (Cr+3) are notsubjected to the required yellow, opaque, and black color. See AppendixX5NOTE 2When fasteners are coated with trivalent chromite
47、 (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 slight irides-cenceC Yellow Yellow iridescentD Opaque Olive green, shading to bro
48、wn or bronzeE Black Black with slight iridescenceF Organic Any of the above plus organic topcoatF1941 1036.3.3 Applicability to Wood Screws and Thread FormingScrewsAny classification code in Table 2 may be applied toscrews that cut or form their own threads.6.3.4 For Supplemental Passivate Finishes,
49、 the minimumrecommended zinc thickness is 5m.6.4 Hydrogen Embrittlement Relief:6.4.1 Requirement for BakingCoated fasteners made fromsteel heat treated to a specified hardness of 40 HRC or above,case-hardened steel fasteners, and fasteners with captive wash-ers made from hardened steel shall be baked to minimize therisk of hydrogen embrittlement. Unless otherwise specified bythe purchaser, baking is not mandatory for fasteners withspecified maximum hardness below 40 HRC.NOTE 3With proper care many steel fasteners can be plated withoutbaking by corr
