1、BRITISH STANDARD BS4479-2: 1990 Design of articles that are to be coated Part 2: Recommendations for electroplated and autocatalytic coatings UDC672/673:62/.795:006:669.857BS4479-2:1990 This British Standard, having been prepared under the direction of the Surface Coatings (other than Paints) Standa
2、rds Policy Committee, was published under the authority of the Board of BSI and comes into effect on 31July 1990 BSI03-1999 First published, as BS4479, August1969 First revision, as BS4479-2July1990 The following BSI references relate to the work on this standard: Committee reference SRC/10 Draft fo
3、r comment86/53497DC ISBN0580179001 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Surface Coatings (other than Paints) Standards Policy Committee (SRC/-) to Technical Committee SRC/10, upon which the following bodies were represented: B
4、ritish Anodising Association Institute of Metal Finishing Institute of Sheet Metal Engineering Institute of Vitreous Enamellers International Tin Research Institute Metal Finishing Association Welding Institute Zinc Development Association Amendments issued since publication Amd. No. Date CommentsBS
5、4479-2:1990 BSI 03-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Design considerations for electroplated articles 1 4 Design considerations for autocatalytically plated articles 3 Appendix A Diagrams illustrating preferred and deprecated desig
6、n features for articles to be electroplated 4 Figure 1 Rolled edges 4 Figure 2 Hollow articles 4 Figure 3 Corners 4 Figure 4 Edges 4 Figure 5 Fins 5 Figure 6 Indentations 5 Figure 7 Protruberances 5 Figure 8 Ribs 5 Figure 9 Slots 6 Figure 10 Bends 6 Figure 11 Blind holes 6 Figure 12 Holes 6 Figure 1
7、3 Overlap joints 7 Figure 14 Welded joints 7 Figure 15 Screwed joints 7 Figure 16 Flat plates 8 Figure 17 Selective plating features 8 Figure 18 Stacking densities 9 Publications referred to Inside back coverBS4479-2:1990 ii BSI 03-1999 Foreword This Part of BS4479 has been prepared under the direct
8、ion of the Surface Coatings (other than Paints) Standards Policy Committee and is based on a draft prepared by the Institute of Metal Finishing. The BSI Technical Committee acknowledges the contribution to this revision by the Institute 1)and by the Committee for the Promotion of Electroplating. Thi
9、s Part of BS4479 is one of a series of Parts which together form a revision of BS4479:1969. On publication of all the Parts, BS4479:1969 will be withdrawn. This revision of BS4479 comprises the following Parts: Part 1: General recommendations; Part 2: Recommendations for electroplated and autocataly
10、tic coatings; Part 3: Recommendations for conversion coatings; Part 4: Recommendations for paint coatings and varnish coatings; Part 5: Recommendations for anodic oxidation coatings; Part 6: Recommendations for hot-dip metal coatings; Part 7: Recommendations for thermally sprayed coatings; Part 8: R
11、ecommendations for vitreous enamel coatings; Part 9: Recommendations for low pressure and vacuum deposited coatings. BS4479 is directed towards helping to maximize the benefit obtained from coating processes. There is a wide variety of coating processes, developed and established industrially, inten
12、ded to enhance or transform the surfaces of manufactured articles. However, time and money are often wasted because the design of many articles is unsuitable for the coating process to be applied. Coating is only one part of the manufacturing process and should not be ignored, or viewed in isolation
13、, when considering the overall costs and quality. This revision of BS4479 has been undertaken to extend the range of coating processes covered. It is not intended to cover every conceivable design detail, type of article or service condition. Adherence to the general principles described will, howev
14、er, greatly assist in the achievement of the desired results. In any case of doubt or difficulty, specialist advice in the particular type of process being considered should be sought. This Part of BS4479 is not a specification and should not be used as such. The recommendations are intended to prov
15、ide guidance towards good practice. 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 obligations. Summa
16、ry of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to10, 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 theinside front
17、 cover. 1) Institute of Metal Finishing.BS4479-2:1990 BSI 03-1999 1 1 Scope This Part of BS4479 gives recommendations for the design of parts that are to be coated by electroplating or autocatalytic plating. This Part of BS4479 applies to the various techniques available for vat and barrel electropl
18、ating, selective electroplating, autocatalytic plating (commonly referred to as electroless plating, though this term is deprecated), but does not give full details of the various processes available for the plating of either metallic or non-metallic surfaces. NOTE 1Many of the basic design recommen
19、dations given are equally applicable to both metallic articles and to those manufactured from other materials, e.g.plastics. NOTE 2It is recommended that Part1 of BS4479 be read in conjunction with this Part. Part1 includes a list of British Standards relating to processes covered by BS4479 but not
20、necessarily referred to in each Part. NOTE 3The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS4479, the following definitions apply. 2.1 electroplated coating a coating obtained by electrodeposition for t
21、he purpose of securing an adherent metallic surface with properties or dimensions different from those of the basis material 2.2 electrodeposition the process of depositing a substance upon an electrode by electrolysis 2.3 autocatalytic coating deposition of a metallic coating by a controlled chemic
22、al reduction that is catalysed by the metal or alloy being deposited NOTEElectroless plating is a deprecated term. 2.4 barrel electroplating a process by which electroplated coatings are applied to articles in bulk in a rotating container 2.5 vat plating a process in which the articles to be electro
23、plated are independently attached to the cathode 2.6 brush electroplating a method of electroplating in which the electrolyte is contained in a pad or brush in contact with the anode. The pad or brush is applied to the part to be processed which is given opposite polarity 2.7 linishing a process whe
24、reby flat surfaces are directionally ground by means of an abrasive bonded to an endless flexible belt 2.8 polishing the smoothing of a metal surface 2.9 electropolishing the smoothing and brightening of a metal surface by making it anodic in an appropriate solution 2.10 chemical polishing immersion
25、 of a metal surface in a solution to produce improved surface smoothness 2.11 significant surface the part of the article covered or to be covered by the coating and for which the coating is essential for serviceability and/or appearance 3 Design considerations for electroplated articles 3.1 General
26、 Plating is a process of depositing a metal, or alloy, on to the surface of an article, usually made of a different metal. It is also possible to deposit metals on to a non-metallic material. Plating can be effected with the aid of an electric current (electroplating) or by immersion in an appropria
27、te solution (autocatalytic plating). There are three main reasons for the application of a metallic coating by electrodeposition: a) to provide an increased resistance to corrosion; b) for decorative purposes; c) for engineering applications. Articles to be plated are normally suspended on wires or
28、jigs in vats, or, in the case of articles that can be handled in bulk, are processed in rotating barrels.BS4479-2:1990 2 BSI 03-1999 Articles that require a polished finish are given a preliminary treatment of grinding or linishing, if necessary, and polishing, or are mass treated in a rotating barr
29、el or vibratory bowl with various abrasive media or polishing compounds. Chemical or electrochemical polishing can be used on certain metals or alloys and may be advantageous on small and intricately shaped articles. Blind holes, recesses and joint crevices, where compound and metal debris can lodge
30、, should be avoided if possible. An electrodeposited coating is generally not distributed uniformly over the surface of an article, but is likely to be thicker at prominences and corners where the current tends to concentrate, and thinner in depressions. Where plated articles have to be fitted toget
31、her, due allowance should be made for the thickness and distribution of the coating, e.g.on screw threads (see also BS3382). The use of autocatalytic processes (see clause4) frequently provides a much more uniform coating thickness on all surfaces. Generally, it is best to avoid large flat areas whi
32、ch can highlight basis metal imperfections. Convex or textured surfaces are to be preferred. Some deposits are less ductile than others and this should be borne in mind when application is considered for articles that might undergo some flexing in fabrication or service. The effect of certain platin
33、g processes on the mechanical properties of some substrates, and, hence, possibly on the serviceability of the coated article should be noted. For example, high strength steels (normally above1000 N/mm 2 ) are particularly susceptible to embrittlement by the hydrogen evolved during the pretreatment
34、or plating processes, and the effect can be relieved by suitable heat-treatment 2) . Consideration should be given to which of the following methods of plating is likely to be the more suitable, in view of the shape and size of the articles: 1) vat plating (see3.2); 2) barrel plating (see3.3); 3) se
35、lective plating (see3.4). Diagrams illustrating preferred and deprecated design features for articles to be electroplated are given in Appendix A. 3.2 Vat plating Account should be taken of the fact that articles to be vat plated should have jigging, or wiring points. They should be either located i
36、n the processing solutions in such a manner that liquid will not be trapped in seams or hollows, or be provided with drainage holes to prevent this problem. Provision of a means for releasing of air or evolved gas should be made where this may become trapped during plating. It is important that the
37、designer clearly indicates those significant surfaces intended to be coated for decorative purposes and/or corrosion protection. This will assist the electroplater in processing to ensure smooth deposits with as even a thickness as possible. The cost of plating a given area on an article will be gre
38、ater if the space occupied by the article in the vat is large. It is sometimes more economical to make the article in sections and assemble them after plating. 3.3 Barrel plating Design may have to take account of non-uniform distribution of coating thicknesses sometimes obtained in barrel plating.
39、Articles should not be prone to interlocking, which can result in damage as well as poor distribution of plating. Flat articles such as washers should be dimpled, if possible, to prevent sticking. Cup-shaped articles may be difficult to immerse in liquids and may drain ineffectively during transfer
40、from one process solution to the next; in such cases suitable drainage holes should be provided where possible. 3.4 Selective plating The following are examples of techniques that are available for the selective plating of articles: a) brush plating; NOTEBrush plating is normally used for local repa
41、ir work although large articles, too big to immerse in a vat can be processed by this method. Numerous metals and alloys can be brush plated and the entire operation is capable off being automated. b) application of a screen-printed or photo-mechanical mask prior to total immersion of the article in
42、 the process solutions; c) application of a mechanical mask for total immersion; d) controlled depth of immersion in the plating solution. 2) Appendix A of BS4479-1:1989 includes a list of some British Standards that give details of suitable treatments. e.g.BS1706 and BS4292-1. Further detailed info
43、rmation may also be found in Engineering coatings applications and properties No.16 in the series of Guides to Practice in Corrosion Control, published by National Corrosion Service of the National Physical Laboratory, obtainable from HMSO.BS4479-2:1990 BSI 03-1999 3 In the case of continuous automa
44、tic selective plating, in which mechanical masks can be used, the work is transported on a bandolier, or continuous strand, through an automatic in-line processing and plating line. The orientation of the articles on the bandolier or strand should permit selective or partial plating to be carried ou
45、t, if possible allowing a choice of techniques. The active area of the article should therefore be presented in the most accessible position. In some cases, a post-forming operation may be necessary and it is important to note that forming of the active area after plating is generally inadvisable. T
46、o facilitate economical processing speeds, the arrangement of articles should avoid line astern configuration. Close pitched ladder formations, with multiple rows, are preferred if possible. The selvedge, carrier bar or bandolier should be sufficiently strong to withstand several S-bends during proc
47、essing, and should be capable of carrying the current for the electrolytic processes used, taking into account the high current densities common to this type of processing. Twist and edge-wise bowing (sabre) should be avoided, if precise selective plating of small areas is required. These adverse ch
48、aracteristics are more serious when a punched strand has more than one carrier bar (see Figure 17 for recommended design practice and tolerances). Pitch errors should not be cumulative and tolerances on all features should generally reflect the precision required in terms of area and location of the
49、 selective plating. If the bandoliered articles are tubular, e.g.socket contacts, they should be free draining and accessible to spray rinses and forced air drying. Components should be easily removable, e.g.for the purposes of testing, without recourse to cutting the strand. 4 Design considerations for autocatalytically plated articles The principal design features given in clause3 for electroplated coatings and illustrated in Appendix A are equally applicable to articles required to be autocatalytically plated. The coating
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