Standard Specification For Coatings Of Zinc Mechanically .

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Designation: B 695 – 00Standard Specification forCoatings of Zinc Mechanically Deposited on Iron and Steel1This standard is issued under the fixed designation B 695; the number immediately following the designation indicates the year oforiginal adoption or, 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This specification covers the requirements for a coatingof zinc mechanically deposited on iron and steel basis metals.The coating is provided in several thicknesses up to andincluding 107 µm. The seven thickest classes are usuallyreferred to as “mechanically galvanized.”1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.B 242 Practice for Preparation of High-Carbon Steel forElectroplating6B 322 Practice for Cleaning Metals Prior to Electroplating6B 487 Test Method for Measurement of Metal and OxideCoating Thicknesses by Microscopical Examination of aCross Section6B 499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis Metals6B 571 Test Methods for Adhesion of Metallic Coatings6B 602 Test Method for Attribute Sampling of Metallic andInorganic Coatings6F 1470 Guide for Fastener Sampling for Specified Mechanical Properties and Performance Inspection72.2 Military Standard:MIL-C-81562 Coating, Cadmium, Tin Cadmium and Zinc(Mechanically Deposited)82.3 AISC Standard:Specifications for Structural Joints Using ASTM A 325 orA 490 Bolts9NOTE 1—The performance of this coating complies with the requirements of Specification A 153 and MIL-C-81562.1.3 The values stated in SI units are to be regarded as thestandard. The inch-pound equivalents of SI units may beapproximate.2. Referenced Documents2.1 ASTM Standards:A 153 Specification for Zinc Coating (Hot–Dip) on Iron andSteel Hardware2A 194/A194M Specification for Carbon and Alloy SteelNuts for Bolts for High-Pressure and High-TemperatureService3A 325 Specification for Structural Bolts, Steel, HeatTreated, 120/105 ksi Minimum Tensile Strength4A 490 Specification for Heat-Treated, Steel StructuralBolts, 150 ksi Minimum Tensile Strength4A 563 Specification for Carbon and Alloy Steel Nuts4B 117 Practice for Operating Salt Spray (Fog) Apparatus5B 183 Practice for Preparation of Low-Carbon Steel forElectroplating63. Classification3.1 Classes—Zinc coatings are classified on the basis ofthickness, as follows:Class110807065555040251285Minimum Thickness, µm1078169665350402512853.2 Types—Zinc coatings are identified by types on thebasis of supplementary treatment required, as follows:Type I—As coated, without supplementary treatment (Appendix X2.1).1This specification is under the jurisdiction of ASTM Committee B-8 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.08.04 on Light Metals.Current edition approved March 10, 2000. Published May 2000. Originallypublished as B 695 – 82. Last previous edition B 695 – 91 (1997).2Annual Book of ASTM Standards, Vol 01.06.3Annual Book of ASTM Standards, Vol 01.01.4Annual Book of ASTM Standards, Vol 15.08.5Annual Book of ASTM Standards, Vol 03.02.6Annual Book of ASTM Standards, Vol 02.05.7Annual Book of ASTM Standards, Vol 01.08.Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.9Available from American Institute of Steel Construction, Inc., 400 N. MichiganAve., Chicago, IL 60611.8Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.1

B 695to avoid the risk of producing hydrogen embrittlement from thecleaning procedure.6.2.3 For low-carbon steels, see Practice B 183. Usefulguidelines are also given in Practice B 322.6.2.4 Mechanical deposition of zinc coatings shall consist,in general, of all of the steps listed below, and in the sequenceas shown: Preparation of the surface of the parts to be coated,by chemical (generally acidic) procedure to an extent thatpermits uniformly satisfactory results from subsequent steps. Deposition of a thin metal coating, generally ofcopper, by immersion in appropriate chemical solutions, without the use of electric current. There are no thickness requirements for this coating. Tumbling of the parts that have been treated according to and in a container with the following:(i) the zinc metal to be deposited, in powder form;(ii) impact media, which may be glass or other substancesthat are essentially inert to the chemicals of the depositionprocess. The function of this media is to aid in providingmechanical forces to drive the metal powder onto the substrateparts;(iii) a “promoter” or “accelerator” which aids in the uniformdeposition of the metal powder;(iv) a liquid medium, generally water. Separation of the parts from the solid and liquidmedia. Rinsing. Drying.6.2.5 Supplementary Treatments: Colored Chromate Conversion Treatments (TypeII)—Colored chromate conversion treatment for Type II shallbe done in a solution containing hexavalent chromium ions.This solution shall produce a bright or semi-bright continuous,smooth, protective film with a uniform color that may rangefrom yellow through bronze and olive-drab to brown and blackand that may be dyed to a desired color. Bright dips that do notcontain salts that yield films containing hexavalent chromiumions are not permitted as treatments for producing Type IIcoatings. Waxes, lacquers, or other organic coatings may beused to improve lubricity, and the need for them shall besupplied in the purchase order or other governing document(see 4.1.1). Supplemental lubrication treatments shall not beused to ensure conformance to the salt spray corrosion resistance requirements (see 8.5.4). Lubrication of grade DH nuts processed in accordance with this specification and used with Specification A 325high-strength bolts is a requirement of paragraph 6.5 ofSpecification A 325 and paragraph 4.8 of Specification A 563.Type II—With colored chromate conversion treatment (Appendix X2.2).4. Ordering Information4.1 To make the application of this standard complete, thepurchaser should supply the following information to the sellerin the purchase order or other governing document:4.1.1 Class, including a maximum thickness, if appropriate,type, and for Type II, color and need for supplemental lubricant(3.1, 3.2, and 6.2.5),4.1.2 Nature of substrate (for example, high-strength steel),need for stress relief (6.2.1), and cleaning precautions to befollowed (6.2.2 and 6.2.3),4.1.3 Significant surfaces (6.3),4.1.4 Requirements for and methods of testing for one ormore of the following, if required: need for and type of testspecimens (8.1), thickness (6.3 and 8.3), adhesion (6.4 and8.4), corrosion resistance (6.5 and 8.5), absence of hydrogenembrittlement, and the waiting period before testing and testingloads (6.6 and 8.6),4.1.5 Inspection responsibility (Section 11) and samplingplan for each inspection criterion (Section 7), and4.1.6 Requirements for certified report of test results (Section 10).5. Workmanship5.1 The coating shall be uniform in appearance and substantially free of blisters, pits, nodules, flaking, and other defectsthat can adversely affect the function of the coating. Thecoating shall cover all surfaces as stated in 6.3 including rootsof threads, thread peaks, corners, recesses, and edges. Thecoating shall not be stained or discolored throughout to anextent that would adversely affect appearance as a functionalrequirement. However, superficial staining, that results fromrinsing or drying, and variations in color or luster shall not because for rejection.NOTE 2—The nature of the mechanical plating process is such thatcoatings characteristically will not be as smooth or as bright as someelectroplated coatings.6. Requirements6.1 Appearance—The coating as deposited shall have auniform silvery appearance, and a matte to medium-brightluster.6.2 Process:6.2.1 Stress-Relief Treatment—All steel parts that have anultimate tensile strength of 1000 MPa and above and thatcontain tensile stresses caused by machining, grinding,straightening, or cold-forming operation shall be given astress-relief heat treatment prior to cleaning and metal deposition. The temperature and time at temperature shall be 190 615 C for a minimum of 3 h so that maximum stress relief isobtained without reducing the hardness below the specifiedminimum.6.2.2 High-strength steels (which become embrittled whencharged with hydrogen) and that have heavy oxide or scaleshall be cleaned before application of the coating in accordancewith Practice B 242. In general, nonelectrolytic alkaline,anodic-alkaline, and some inhibited acid cleaners are preferredNOTE 3—Although not included in Specification A 194/A 194M, thisprovision should apply to mechanically galvanized A 194 2H nuts whensupplied for use with Specification A 325 bolts.NOTE 4—Specifications for structural joints using Specification A 325or A 490 bolts references the use of lubricants on nuts to be used withSpecification A 325 high-strength bolts and is found in the commentary onthis RCSC (Research Council on Structural Connections of the Engineering Foundation) Specification, within the paragraphs entitled “Effect Of2

B 6956.5.1 The presence of corrosion products visible to theunaided eye at normal reading distance at the end of thespecified test periods stated in Table 1 shall constitute failure,except that corrosion products at edges of specimens shall notconstitute failure. Slight “whisps” of white corrosion, asopposed to obvious accumulations, shall be acceptable.Galvanizing Upon Torque Involved In Tightening” and “Shipping Requirements For Galvanized Bolts and Nuts,” published November 1985,page Surface Defects—Defects and variations in appearance in the coating that arise from surface conditions of thesubstrate (scratches, pores, roll marks, inclusions, etc.) and thatpersist in the finish despite the observance of good metalfinishing practices shall not be cause for rejection.NOTE 8—Mechanical deposition is exclusively a barrel-finishing process. It is recognized that mechanical deposition on parts may thereforeproduce surfaces that have a different characteristic from those on partsthat are finished exclusively by racking. Similarly, corrosion testing ofactual parts may produce different results from those on test panels. Saltspray requirements that are appropriate to indicate the technical qualitywith which a process is carried out may be impractical for acceptance ofactual parts. In such cases the purchaser shall indicate his requirements onthe purchase order (4.1.4).NOTE 9—In many instances, there is no direct relation between theresults of an accelerated corrosion test and the resistance to corrosion inother media, because several factors that influence the progress ofcorrosion, such as the formation of protective films, vary greatly with theconditions encountered. The results obtained in the test should not,therefore, be regarded as a direct guide to the corrosion resistance of thetested materials in all environments where these materials may be used.Also, performance of different materials in the test cannot always be takenas a direct guide to the relative corrosion resistance of these materials inservice.NOTE 5—Applied finishes generally perform better in service when thesubstrate over which they are applied is smooth and free of torn metal,inclusions, pores, and other defects. It is recommended that the specifications covering the unfinished product provide limits for these defects. Ametal finisher can often remove defects through special treatments, suchas grinding, polishing, abrasive blasting, chemical treatments, and electropolishing. However, these are not normal in the treatment stepspreceding the application of the finish. When desired they must bespecified on the purchase order (4.1.2).6.3 Thickness:6.3.1 The thickness of the coating everywhere on thesignificant surfaces shall be at least that of the specified classas defined in Significant surfaces are defined as those normallyvisible (directly or by reflection) that are essential to theappearance or serviceability of the article when assembled innormal position; or that can be the source of corrosion productsthat deface visible surfaces on the assembled article. Whennecessary, the significant surfaces shall be indicated on thedrawing for the article, or by the provision of suitably markedsamples.6.5.2 On parts with Type II coatings, the greater number ofhours for either white corrosion products or rust shall apply.For example, for Type II, Class 8, the test shall be continueduntil the 72-h requirement is met for white corrosion products;similarly, for Type II, Class 25, if no white corrosion productsappear before 72 h, test shall be continued until the 192-hrequirement for basis metal corrosion is met (8.5.2).6.6 Absence of Hydrogen Embrittlement—Springs and otherhigh-strength parts subject to flexure shall be held for aminimum of 48 h at room temperature after coating beforebeing loaded, flexed, or used. Such high-strength steel partsshall be free of hydrogen embrittlement. When specified in thepurchase order, freedom from embrittlement shall be determined by the test specified herein (4.1.4 and 8.6).NOTE 6—The thickness of mechanically-deposited coatings varies frompoint-to-point on the surface of a product, characteristically tending to bethicker on flat surfaces and thinner at exposed edges, sharp projections,shielded or

2 Annual Book of ASTM Standards, Vol 01.06. 3 Annual Book of ASTM Standards, Vol 01.01. 4 Annual Book of ASTM Standards, Vol 15.08. 5 Annual Book of ASTM Standards, Vol 03.02. 6 Annual Book of ASTM Standards, Vol 02.05. 7 Annual Book of ASTM Standards, Vol 01.08. 8 Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700 Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS .

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