1、BRITISH STANDARD BS 7371-10: 1994 Coatings on metal fasteners Part 10: Specification for organic coatings UDC 621.88:667.622.3BS7371-10:1994 This British Standard, having been prepared under the directionof the General Mechanical Engineering Standards Policy Committee, waspublished under the authori
2、tyof the Standards Boardand comes into effect on 15 March1994 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference GME/9 Draft for comment93/709784 DC ISBN 0 580 22769 3 Committees responsible for this British Standard The preparation of this British Stan
3、dard was entrusted by the General Mechanical Engineering Standards Policy Committee (GME/-) to Technical Committee GME/9, upon which the following bodies were represented: BEAMA Ltd. British Constructional Steelwork Association Ltd. British Industrial Fasteners Federation British Steel Industry Brit
4、ish Steel Industry (Wire Section) Gauge and Tool Makers Association Society of Motor Manufacturers and Traders Ltd. Washer Manufacturers Association of Great Britain The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Turned-parts Man
5、ufacturers Association Institute of Metal Finishing Metal Finishing Association Stainless Steel Fabricators Association of Great Britain National Centre of Tribology Amendments issued since publication Amd. No. Date CommentsBS7371-10:1994 BSI 09-1999 i Contents Page Committees responsible Inside fro
6、nt cover Foreword ii 0 Introduction 1 1 Scope 1 2 References 2 3 Definitions 2 4 Applications and type of coating 2 5 Coating 2 6 Gauging after coating for threaded fastener components 3 7 Information to be supplied 3 8 Identification 3 Annex A (normative) Adhesion test 4 Annex B (informative) Suita
7、bility of organic coatings for threaded fasteners 4 Table 1 Corrosion resistance 2 Table B.1 Organic coatings for male threaded fasteners to be used withtolerance class H threaded female fasteners 4 Table B.2 Organic coatings for female threaded fasteners to be used withtolerance class g threaded ma
8、le fasteners 4 Table B.3 Organic coatings for male/female thread combinations 5 List of references Inside back coverBS7371-10:1994 ii BSI 09-1999 Foreword This Part of BS7371 has been prepared under the authority of the General Mechanical Engineering Standards Policy Committee to provide part of a s
9、eries of standards on coatings on metal fasteners. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obl
10、igations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the
11、 inside front cover.BS7371-10:1994 BSI 09-1999 1 0 Introduction BS7371 deals with the performance and selection of coatings on metal fasteners and accessories. This Part of BS7371 specifies the requirements for organic coatings. Other published Parts of BS7371 are as follows: BS7371-1:1991 Specifica
12、tion for general requirements and selection guidelines 1) BS7371-2:1993 Specification for torque/clamping force relationship BS7371-3:1993 Specification for electroplated zinc and cadmium coatings BS7371-7:1994 Specification for mechanically applied zinc coatings BS7371-11:1993 Specification for zin
13、c flake non-electrolytically applied cured coatings Further Parts of the series to incorporate the following are in preparation: Specification for electroplated nickel, nickel/chromium and copper/nickel/chromium coatings Specification for electroplated tin and tin/lead coatings Specification for ele
14、ctroplated coatings for special purposes Specification for mechanically applied coatings for special purposes Specification for phosphate and oil coatings Organic coatings covered by this Part of BS7371 are for use on fasteners and accessories where the following apply: a) a colour is required; b) t
15、he risk of hydrogen embrittlement of high tensile steel fasteners is unacceptable; c) a more even coverage of parts of complex shape than would be obtained by electroplated metallic coatings is advantageous. The corrosion resistance of an organic coating is principally dependant upon the barrier eff
16、ect such that when any base metal is exposed corrosion may occur. Organic coatings which are oiled will inhibit this effect by migration of the oil. The coatings may also inhibit electrical conductivity. Organic coatings may be applied over other coatings such as phosphate or zinc in order to improv
17、e corrosion resistance or impart a colour. The shape of certain parts may create difficulties in the application of these coatings and reference to the coater is recommended to enquire if a difficulty exists or if it can be overcome by the use of specialized processing methods. Typical difficulties
18、arise when bulk processing: 1) parts with flat surfaces that can stick together during processing, e.g.flat washers; 2) parts with shapes that induce nesting and interlocking; 3) parts with recesses. The coatings are suitable for application to metal components such as the following: i) parallel thr
19、eaded fasteners and accessories: ii) screws that cut or form their own threads, e.g.self tapping screws (see for example BS4174:1972); iii) woodscrews (see for example BS1210:1963); iv) springs and spring components; v) pipe nuts and connectors with parallel or tapered threads; When these coatings a
20、re applied to non-ferrous fasteners, the only part of the specification that will apply will be the coating thickness requirements. NOTEThe processing temperature of certain coatings complying with this standard may adversely affect the mechanical properties of some heat treated components. 1 Scope
21、This Part of BS7371 specifies requirements for organic coatings. The coatings consist principally of pigments and other additives bonded by resins and can be lubricated to give controlled torque/clamping force properties when required (see for example BS7371-2:1993). In addition to the requirements
22、in this Part of BS7371, the requirements in Part1 of the standard which are applicable to organic coatings apply. This Part of BS7371 also specifies requirements for the following: a) four grades of coating; b) colour; c) quality assessment of the corrosion resistance of unused coated parts when sub
23、jected to neutral salt spray testing (see for example BS7479:1991); d) adhesion test. 1) This is supplementary to all other Parts of BS7371.BS7371-10:1994 2 BSI 09-1999 2 References 2.1 Normative references This Part of BS7371 incorporates, by reference, provisions from specific editions of other pu
24、blications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. Subsequent amendments to, or revisions of, any of these publications apply to this Part of BS7371 only when incorporated in it by updating or revision. 2.2
25、 Informative references This Part of BS7371 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Definitions For the
26、purposes of this Part of BS7371, the definitions given in BS7371-1:1991 apply together with the following. organic coating a coating which consists of pigments and other additives bonded together by resins 4 Applications and type of coating 4.1 Cleaning and pretreatment Parts, fasteners and accessor
27、ies shall be cleaned and pretreated in accordance with clauses4 and5 of BS7371-1:1991. NOTEA phosphating pretreatment is permitted to improve adhesion or corrosion resistance, this may reduce the electrical conductivity and parts which have a phosphate pretreatment may require de-embrittlement if th
28、e curing temperature of the organic coating does not exceed180 C. 4.2 Type of coating The coating shall consist primarily of resins incorporating additives and pigments to improve corrosion resistance or to impart colour or lubricity. Where specified by the purchaser see itemd) of clause7) the lubri
29、city of the coating shall be modified by the addition of a lubricant and the torque/clamping force performance of a coated fastener shall conform to BS7371-2:1993. NOTEUnless otherwise specified oil impregnation may be used to improve corrosion resistance or to provide lubricity, resulting in coatin
30、gs which are not completely dry. 4.3 Curing of coating The coating shall be cured and the curing temperature shall not exceed230 C. 5 Coating 5.1 Surface condition The coating shall be clean and of uniform appearance. All surfaces of a component shall be coated unless otherwise agreed. The coating s
31、hall be free from blisters, nodules or loosely adhering material. 5.2 Colour The colour of the coating on individual components shall be uniform in appearance and in the mid-range of the designated colour. Slight variations in colour between components shall not be cause for rejection unless otherwi
32、se agreed between the purchaser and supplier. NOTEColour matching and gloss level may be specified by the purchaser on agreement with the supplier. 5.3 Corrosion resistance Unless otherwise agreed, representative samples from a batch shall be tested in accordance with clause7 of BS7371-1:1991 and sh
33、all be tested for resistance to neutral salt spray in accordance with BS7479:1991. Coatings shall be graded by their corrosion resistance as given in Table 1. Significant surfaces shall resist neutral salt spray for the time given in Table 1. Surfaces which are not significant shall resist neutral s
34、alt spray for50% of the time given in Table 1. NOTECoating weight and thickness are not reliable parameters for confirmation of the corrosion resistance of organic coatings since they give no indication of porosity. Therefore, for referee purposes the corrosion resistance requirements still apply. 5
35、.4 Adhesion When tested in accordance with Annex A the exposure of more than10% of the base metal over the tested area shall constitute failure. Parts which do not have significant surfaces of sufficient size or shape to permit testing in accordance with Annex A shall be assessed by testing parts co
36、ated by the same process in the same production run. Oil impregnated parts shall be either tested prior to the application of the lubricant or after removal of the lubricant with a cold solvent that does not attack the organic coating. NOTEPick up of some colouration on the tape is permissible. Tabl
37、e 1 Corrosion resistance Grade Resistance of neutral salt spray, time for basemetal corrosion (min.) h OA OB OC OD 72 120 192 240 NOTEAll grades are available with controlled lubricity.BS7371-10:1994 BSI 09-1999 3 6 Gauging after coating for threaded fastener components After coating, the finished t
38、hreaded fastener component shall conform to the following. a) A coating, externally threaded component shall assemble into a similarly threaded nut with thread of tolerance class6H in conformance with BS3643-2:1981. b) A coated internally threaded component shall assemble onto a similarly threaded b
39、olt with thread of tolerance class6g in conformance with of BS3643-2:1981. NOTEFor the suitability of organic coatings for threaded fasteners see Annex B. 7 Information to be supplied The following information shall be fully documented: a) the number of this British Standard, i.e.BS7371-10:1994; b)
40、the coating grade; c) the colour; d) the requirements of a coating lubricated to BS7371-2:1993; e) dry or oiled, if not defined either condition may be supplied; f) any additional information regarding limitations of the process to be used, e.g.maximum acceptable coating thickness, any restrictions
41、in coating material, metallurgical condition details if the curing temperature may have some effect on heat treated parts. 8 Identification The coating shall be identified by the number and date of this British Standard, i.e.BS7371-10:1994 2)together with the grade. The grade shall be selected from
42、Table 1. A colour shall be identified by the colour name written after the grade identification. NOTE 1In the absence of a colour in the designation the colour black may be supplied. A lubricated condition shall be identified by the letter L after the colour or grade identification as applicable (se
43、e4.2). A requirement for the coating to be supplied dry or oiled shall be designated by either1 for oiled or2 for dry after the dry lubricant, colour or grade identification as applicable. NOTE 2In the absence of any designation either condition may be supplied. For example a dry green organic coati
44、ng of grade OA with controlled lubricity would be identified as BS7371-10:1994 grade OA green L2. 2) Marking BS7371-10:1994 on or in relation to a product represents a manufacturers declaration of conformity, i.e.a claim by or on behalf of the manufacturer that the product meets the requirements of
45、the standard. The accuracy of the claim is solely the claimants responsibility. Such a declaration is not to be confused with third party certification of conformity, which may also be desirable.BS7371-10:1994 4 BSI 09-1999 Annex A (normative) Adhesion test Using a sharp instrument, scribe lines thr
46、ough to the base metal approximately2mm apart across a significant surface of the component, then scribe further lines at approximately90 to these. Apply a strip of clear tape conforming to BS3887:1991 and rub down with finger pressure. Remove the tape within(90 30)s of application by pulling it off
47、 rapidly and smoothly, back upon itself, as closely as possible to an angle of180 to the coated surface. Annex B (informative) Suitability of organic coatings for threaded fasteners B.1 General The suitability of the specified coatings for threaded parts is limited by the clearance between external
48、and internal threads. Table B.1, Table B.2 and Table B.3 give guidance on the grades of coating that can be applied to standard threads to limit the risk of interference. B.2 Avoidance of thread interference forthreads in conformance with Part2 of BS3643 Table B.1 shows grades of coating which may b
49、e safely applied to male threaded parts with thread tolerance classes g, f or e, before coating, which are to be mated after coating with uncoated female threads tolerance class H. Table B.2 shows grades of coating which may be safely applied to female threaded parts with thread tolerance classes H or G, before coating, which are to be mated after coating with uncoated male threads tolerance class g. Table B.3 shows grades of coatings which may be safely applied if both male and female threaded parts are to be coated. NOTEThe fundamental deviations for ea
