1、Designation: F 1941 00 (Reapproved 2006)Standard 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
2、, in the case of revision, 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 fas
3、teners by electrodepo-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 transgresse
4、d by either the internal 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 hav
5、ing ahardness 40 HRC 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.Th
6、erefore, the application of a metallic coating by electrodeposition is not recommended for suchfasteners.1. Scope1.1 This specification covers application, performance anddimensional requirements for electrodeposited coatings onthreaded fasteners with unified inch screw threads. It specifiescoating
7、thickness, supplementary chromate finishes, corrosionresistance, precautions for managing the risk of hydrogenembrittlement and hydrogen embrittlement relief for high-strength and surface-hardened fasteners. It also highlights thedifferences between barrel and rack plating and makes recom-mendations
8、 as to the applicability of each process.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 The following precautionary statement pertains to thetest method portion only, Section 9, of this specification: Thisstandard does
9、 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 Documents2.1 ASTM Standar
10、ds:2B117 Practice for Operating Salt Spray (Fog) ApparatusB 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: Nonmagnetic Coatings onMagnetic Basis Metals
11、B 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 for Measurement of Coating Thicknessby X-Ray SpectrometryB 659 Guide for Measuring Thickness of Metallic
12、 andInorganic CoatingsE 376 Practice for Measuring Coating Thickness byMagnetic-Field or Eddy-Current (Electromagnetic) Exami-nation Methods1This specification is under the jurisdiction of ASTM Committee F16 onFasteners and is the direct responsibility of Subcommittee F16.03 on Coatings onFasteners.
13、Current edition approved June 1, 2006. Published June 2006. Originallyapproved in 1998. Last previous edition approved in 2000 as F 1941 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volum
14、e information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.F 606 Test Methods for Determining the Mechanical Prop-erties of Externally and Internally Threaded Fasten
15、ers,Washers, 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 toPrev
16、ent 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. Termin
17、ology3.1 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 specif
18、iednumber 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
19、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 signi
20、ficantsurfaces 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
21、2:4.3 Chromate Finish The chromate finish shall be se-lected and designated in accordance with Table 3.5. Ordering Information for Electroplating5.1 When ordering threaded fasteners to be coated byelectrodeposition in accordance with this specification, thefollowing information shall be supplied to
22、the electroplater:5.1.1 The desired coating, coating thickness and the chro-mate finish, or the classification codes as specified in Tables1-3. (for example, Fe/Zn 5C denotes yellow zinc plated with aminimum thickness of 0.0002 in. on significant surfaces.)5.1.2 The identification of significant sur
23、faces (optional).5.1.3 The requirement, 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 fas
24、teners and/or baking time andtemperature.NOTE 1Fasteners with a specified maximum hardness of 34 HRC and3Available from American Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Three Park Ave., New York, NY 10016-5990.4Available from Standardization Documents Order Desk, DODS
25、SP, 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 Externally Threaded FastenersNOTE 1Black dot ()
26、 indicates test surface.FIG. 2 Significant Surfaces on Internally Threaded FastenersTABLE 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 Thickne
27、ssNOTE 1The conversion factor 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 0.0005F 1941 00 (2006)2below have a very low susceptibility to hydrogen embrittlement and donot require baking.5.1.5 The requirement
28、s, if any, for the type of electroplatingprocess (barrel-plating or rack-plating). See Section 10 andAppendix X1.5.1.6 The designation of coated thread class shall complywith ASME B1.1.6. Requirements6.1 Coating RequirementsThe electrodeposited coating asordered shall cover all surfaces and shall me
29、et the followingrequirements:6.1.1 The coating metal deposit shall be bright or semi-bright unless otherwise specified by the purchaser, 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 def
30、ects that willaffect the function of the coating.6.1.3 The coating shall not be stained, discolored or exhibitany evidence of white 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 stai
31、ning that results from rinsing shall not be cause forrejection.6.2 Corrosion ResistanceCoated fasteners, when testedby continuous 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
32、theend of the test period. The appearance of corrosion productsvisible to the unaided eye at normal reading distance shall because 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 cadmium
33、coatings.6.3 ThicknessThe coating thickness shall comply withrequirements of Table 2 when measured in accordance with9.1.6.3.1 Restrictions on Coating ThicknessThis specificationimposes minimum local thickness requirements at significantsurfaces in accordance with Table 2. Thick or thin localthickne
34、ss in a location other than a significant surface shall notbe a cause for rejection. However the following restrictionsapply:6.3.1.1 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 Ex
35、ternal Threads Maximum coating thickness athigh current density threaded tips must provide for class 3AGO thread gauge acceptance.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, hole
36、s, deep recesses, basesof angles, and similar areas on which the specified thickness ofdeposit cannot readily be controlled, are exempted fromminimum thickness requirements unless they are speciallydesignated as not being exempted. When such areas are subjectto minimum thickness requirements, the pu
37、rchaser and themanufacturer shall recognize the necessity for either thickerdeposits on other areas or special racking.6.3.2 Applicability 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
38、 hence limited by the pitch diameter, allowance andtolerance positions. Refer to Appendix X3 as a guideline forthe tolerances of 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
39、 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 fact thatdimensional allowance of most threaded fasteners normallydoes not permit it. If the size of the fastener is large enough toeconomically use the rac
40、k-plating process, then the latter shallbe used to obtain this thickness requirement. If heaviercoatings are required allowance for the deposit 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
41、 applied toscrews that cut or form their own threads.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
42、 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 2With proper care many steel fasteners can be plated withoutbaking by correlating process conditions to the susc
43、eptibility of thefastener 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 betweenth
44、e supplier and the purchaser, 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 c
45、onsidered 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 process and cathodic
46、efficiency of the electroplatingprocess used. The baking conditions shall be selected based onthe results of recognized embrittlement test procedures such asTest Methods F 606, F 1624, F 1940, or NASM13125.TABLE 3 Designation of Chromate FinishDesignation Type Typical AppearanceA Clear Transparent c
47、olorless with slight iridescenceB Blue-bright Transparent with a bluish tinge and slightiridescenceC Yellow Yellow iridescentD Opaque Olive green, shading to brown or bronzeE Black Black with slight iridescenceF Organic Any of the above plus organic topcoatF 1941 00 (2006)36.4.2.1 Bake time and temp
48、eratures may require lowering tominimize the risk of solid or liquid metal embrittlementresulting from alloy compositions such as those containing leador from the lower melting point of cadmium (610F) incomparison to zinc (786F).6.4.2.2 Fasteners must be baked within 4 h, preferably 1 hafter electro
49、plating. Baking to relieve hydrogen embrittlementmust be performed prior to the application of the chromatefinish because temperatures above 150F damage the chromatefilm thereby negating its performance.6.4.3 Hydrogen Embrittlement TestingHydrogen em-brittlement testing is mandatory for fasteners with a specifiedhardness of 40 HRC or above unless the electroplating processhas been qualified in accordance with Test Method F 1940 (thatis, the process has been shown not to cause embrittlement fora given product or class of product). This specification
