1、BRITISH STANDARD CONFIRMED MARCH1990 BS 3597:1984 Specification for Electroplated coatings of 65/35tin/nickel alloy UDC 669.058.7:669.6524:621.357.7BS 3597:1984 This British Standard, having been prepared under the directionof the Surface Coatings (other than Paints) Standards Committee, was publish
2、ed underthe authority of the Board ofBSI and comes into effect on 29February1984 BSI 08-1999 First published April 1963 First revision February 1984 The following BSI references relate to the work on this standard: Committee reference SRC/3 Draft for comment 81/50222 DC ISBN 0 580 13665 5 Committees
3、 responsible for this British Standard The preparation of this British Standard was entrusted by the Surface Coatings (other than Paints) Standards Committee (SRC/-) to Technical Committee SRC/3 upon which the following bodies were represented: British Metal Finishing Suppliers Association British T
4、elecommunications Electronic Components Industry Federation Electronic Engineering Association Institute of Metal Finishing International Tin Research Institute Metal Finishing Association Ministry of Defence Telecommunication Engineering and Manufacturing Association (TEMA) Amendments issued since
5、publication Amd. No. Date of issue CommentsBS3597:1984 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definition 1 3 Information to be supplied by the purchaser to the electroplater 1 4 Coating classification 1 5 Sampling 2 6 Heat treatment of steel 2 7
6、 Undercoats 2 8 Coatings 2 Appendix A Guidance information 4 Appendix B Determination of local undercoat thickness and coating thickness 5 Appendix C Adhesion test (thermal shock method) 5 Appendix D Sulphur dioxide porosity test 5 Figure 1 Cabinet with door 7 Figure 2 Hooded cabinet 8 Table 1 Servi
7、ce condition and related recommended coating thickness 5 Table 2 Oven temperature 5 Publications referred to Inside back coverBS 3597:1984 ii BSI 08-1999 Foreword This British Standard has been prepared under the direction of the Surface Coatings (other than Paints) Standards Committee. It applies t
8、o electroplated coatings of the65/35 (nominal) tin/nickel alloy on ferrous and non-ferrous metals as a hard, wear- and corrosion-resistant finish in both engineering and decorative fields. It is a revision of the1963 edition, which is withdrawn, the main changes from which are: a) combination of the
9、 four separate tables for thickness requirements applicable to different substrates into a single list of preferred thicknesses; b) inclusion, as an appendix, of guidance notes drawing the attention of theuser to factors which should be taken into account when electroplating with65/35 tin/nickel all
10、oy; c) deletion of the post-electroplating heat treatment recommendations for relief of hydrogen embrittlement because65/35 tin/nickel alloy coatings are now known to be virtually impervious to hydrogen; d) rationalization of the coating thicknesses recommended for different service conditions; e) d
11、eletion of the “strip and weigh” method for determination of average coating thickness because it is now recognized that there is no suitable stripping solution. It is essential, when specifying to BS3597, that the purchaser shouldstate the classification code and the other information listed in3.1
12、(and, if appropriate,3.2). Merely to ask for the electroplating to be carried out to BS3597 without this information is insufficient. 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. C
13、ompliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may
14、 have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS3597:1984 BSI 08-1999 1 1 Scope This British Standard specifies requirements for electroplated coatings of the intermatallic compound SnNi. NOTE 1Such coatings are generally recognized as bei
15、ng hard and wear- and corrosion-resistant. The coatings are intended for use on ferrous and non-ferrous basis metals and also on printed wiring boards. A classification scheme is included by which the nature of the basis metal and undercoat, if any, and the tin/nickel coating thickness can be define
16、d. This standard does not specify any requirements for the condition, finish or surface roughness of the basis material before electroplating (seeA.3). NOTE 2Attention is drawn to BS9760, which specifies capability approval procedure and rules for printed circuits of assessed quality. The standard i
17、s not applicable to electroplating of: a) threaded components; b) sheet, strip or wire in the unfabricated form, or of coil springs; c) steels with tensile strengths greater than1000MPa, because such steels require hydrogen embrittlement relief after plating (seeclause6). NOTE 3The titles of the pub
18、lications referred to in this standard are listed on the inside back cover. 2 Definition For the purposes of this standard, the following definition, together with those given for other terms in BS5411-1, applies. significant surface the part of the article covered or to be covered by the coating an
19、d for which the coating is essential for serviceability and/or appearance 3 Information to be supplied by the purchaser to the electroplater 3.1 Essential information. The following information shall be supplied by the purchaser to the electroplater: a) the number of this standard, i.e. BS3597; b) t
20、he nature of the basis material; c) the classification code of the coating required (see clause4); d) the significant surface of the article to be electroplated, indicated, for example, by drawings or by the provision of suitably marked samples; e) the sampling procedure to be adopted (seeclause5);
21、f) the positions where unavoidable contact marks and other defects are acceptable (see8.1). 3.2 Additional information. The following additional information may be required, and if so, shall be specified by the purchaser, if necessary in consultation with the electroplater: a) whether any heat treat
22、ment, with the exception of that specified in clause6 for certain steels, is required before electroplating; b) whether, for coatings whose minimum thickness is104m or greater, the porosity test ofAppendix D is to be applied (see8.4), and if so: 1) the type, number, shape and dimensions of the test
23、specimens to be used and whether cut edges to test specimens are to be protected; 2) the total exposed surface area of the specimen or specimens to be tested at one time, and the angle of inclination of flat test specimens, if other than that specified inD.4; c) whether the adhesion test ofAppendix
24、C is to be applied (see8.3); d) undercoats: 1) for a basis material of steel, iron or iron alloy and where the coating thickness is104m or greater, which method is to be used to determine the required undercoat thickness; 2) whether an undercoat (or undercoats) is required for basis materials other
25、than described in item d) 1) above, and if so: i) its nature and minimum local thickness (seeA.3 andA.4); ii) which method is to be used to determine the required undercoat thickness; e) which method is to be used to determine the required coating thickness (see8.2); f) whether any special pretreatm
26、ent is required. If necessary, the purchaser shall supply a sample showing the required finish. 4 Coating classification Coatings shall be classified by a code consisting of three parts, each of which shall be separated by an oblique stroke, as follows: a/b/cBS 3597:1984 2 BSI 08-1999 where Example.
27、 Fe/Cu/SnNi 10 represents a ferrous basis metal with a copper undercoat, tin/nickel electroplated to a thickness of104m. 5 Sampling The method of sampling shall be selected from the procedures given in either BS6001 or BS6041. NOTEThe acceptance levels should be agreed between the purchaser and supp
28、lier. 6 Heat treatment of steel Severely cold-worked steel parts shall be stress-relieved before electroplating by either: a) heating for1h at a temperature of190 C to230 C; or b) where treatment as in item a) would impair some steels which have been carburized, flame hardened or induction hardened
29、and subsequently ground, heating at a lower temperature, e.g. at170 C for not less than1h. NOTEHydrogen embrittlement relief after electroplating. Because diffusion of hydrogen through tin-nickel coatings is very slow, heat treatment for hydrogen embrittlement relief after electroplating is impracti
30、cal. 7 Undercoats 7.1 General. For coating thicknesses of104m and greater, an undercoat of copper, nickel, bronze or tin of minimum local thickness84m shall be applied on ferrous basis materials; In other cases where an undercoat is specified, its nature and minimum local thickness shall be specifie
31、d by the purchaser (seeA.3, A.4 andA.5). 7.2 Thickness. The thickness of any undercoat (or undercoats) shall be determined by either: a) one of the methods given in Appendix B, as specified by the purchaser; or b) any other method that the purchaser specifies, provided that it can be demonstrated to
32、 have an accuracy of10% or better of the true local thickness, or is as good as or better than the methods given inAppendix B for the particular application. The method specified shall be the one that is expected to yield the most reliable results considering such factors as shape of component, size
33、of component, undercoat material, basis material, etc. In case of dispute, the microscopical method referred to inB.1 shall be used. 8 Coatings 8.1 Appearance. When examined by normal or corrected vision without other aid, the significant surface(s) of the electroplated article shall be clean, free
34、from visible defects such as blisters, pits, roughness, cracks or unplated areas and shall not be stained or discoloured. The acceptability of defects on non-significant surfaces and the position of unavoidable contact marks shall be specified by the purchaser. If necessary, a sample showing the req
35、uired finish shall be supplied or approved by the purchaser. 8.2 Thickness. The minimum thickness ofthetin/nickel coating shall be specified in thecoating classification code see3.1 c), clause4, andA.6 from within the range 5 4m to254m andthe preferred thickness values shall be54m, 104m, 154m and254
36、m. The thickness of the coating shall be measured over a reference area (see BS5411-1) on any part of the significant surface that can be touched with a20mm diameter ball. In the case of articles having a significant surface area of100mm 2or greater, the minimum thickness shall be regarded as the mi
37、nimum value of local thickness. In the case of articles having a significant surface area of less than100mm 2 , the minimum thickness shall be regarded as the minimum value of average thickness (seeA.5). The thickness of the coating shall be determined by either: a) one of the methods given in Appen
38、dix B, as specified by the purchaser; or b) any other method the purchaser specifies, provided that it can be demonstrated to have an accuracy of10% or better of the true thickness, or is as good as or better than the methods given inAppendix B for the particular application. a indicates the chemica
39、l symbol for the basis metal (or for the main constituent if an alloy); b indicates the undercoat, by the symbol “Ni” or “Cu” in the case of nickel or copper, or by the symbol “u” where other undercoat materials or systems are required see3.2 d), or by the symbol “z” where an undercoat is not requir
40、ed; c indicates the type of coating by means of the symbol “SnNi”, followed by the minimum coating thickness, in 4m.BS3597:1984 BSI 08-1999 3 The method specified shall be one that is expected toyield the most reliable results considering such factors as coating thickness, shape of component, size o
41、f component, coating material, basis material,etc. In the case of dispute, the microscopical method referred to inB.1 shall be used. 8.3 Adhesion. If specified by the purchaser, coatings shall be subjected to the adhesion test described inAppendix C, when there shall be no evidence of coating detach
42、ment. 8.4 Porosity. If specified by the purchaser, coatings having a minimum thickness of104m or greater shall be subjected to a porosity test as follows: a) for ferrous basis material, the test given inBS5466-1; b) for non-ferrous basis material, the test given inAppendix D. The result of the test
43、shall be subjected to the procedure described in BS3745 and a “rating number” obtained which shall be either: a) greater than or equal to9, if the coating thickness is254m or greater; or b) greater than or equal to that specified by the purchaser, if the coating thickness is104m or greater, but less
44、 than254m.BS 3597:1984 4 BSI 08-1999 Appendix A Guidance information A.1 General The information in this appendix is intended to draw the attention of the user to: a) certain properties of the tin/nickel alloy which, if not appreciated, may lead to inappropriate use of the coating; b) properties and
45、 preparation of the basis material; c) electroplating practice. A.2 Properties of the coating Electroplated tin/nickel alloy is a single-phase, metastable compound corresponding approximately to the formula SnNi. Although the alloy does not melt below800 C, phase transformation occurs atelevated tem
46、peratures and the maximum safe working temperature of the deposit is considered tobe about 300 C. The coating is hard (about750HV), inherently brittle, and it is inadvisable to carry out fabrication involving deformation after electroplating. Furthermore, where appearance is important, the coating s
47、hould not be applied to parts subject to deformation or vibration in service. Because of the brittle nature of the alloy, the use of coatings thicker than254m is not generally recommended. The brightness of the “as-electroplated” tin/nickel alloy is related to that of the substrate but tends to decr
48、ease with increasing thickness. (See alsoA.3.) On exposure to air, tin/nickel alloy readily forms a passive oxide film that provides excellent resistance to corrosion except in certain strongly acid environments. The coating is more “noble” than most common metals and basis metal exposed at pores ma
49、y therefore be subjected to a more intense local corrosive attack. For this reason, low porosity of the coating is the most important requirement if corrosion resistance is required. For some applications, for example when tin/nickel is used because of its low coefficient of friction or for its high wear-resistance, the presence of porosity may not be significant and may even be advantageous if oil-retention is required. Unlike tin coatings, tin/nickel alloy is not subject to either whisker growth or allotropic change. However, it should be noted that undesirab
