1、BRITISH STANDARD BS4479-4: 1990 Design of articles that are to be coated Part4: Recommendations for paint coatings and varnish coatings UDC672/673:621.795:006BS4479-4:1990 This British Standard, having been prepared under the directionof the Pigments, Paintsand Varnishes StandardsPolicy Committee, w
2、aspublished under the authorityof the Board of BSI andcomes into effect on 31 July1990 BSI04-1999 First published, as BS4479, August1969 First revision, as BS4479-4 July1990 The following BSI references relate to the work on this standard: Committee reference PVC/27 Draft for comment86/54669 DC ISBN
3、 0 580 17902 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Pigments, Paints and Varnishes Standards Policy Committee (PVC/-) to Technical Committee PVC/27, upon which the following bodies were represented: Aluminium Coatings Associat
4、ion Aluminium Federation Aluminium Window Association British Railways Board British Tar Industry Association British Telecommunications plc Consumer Policy Committee of BSI Department of the Environment (Building Research Establishment) Department of Trade and Industry (Laboratory of the Government
5、 Chemist) Electricity Supply Industry in England and Wales Institute of Metal Finishing Institute of Petroleum Institution of Corrosion Science and Technology Institution of Structural Engineers Institution of Water and Environmental Management (IWEM) London Regional Transport METCON Ministry of Def
6、ence Oil and Colour Chemists Association Paint Research Association Paintmakers Association Society of Chemical Industry Steel Window Association Union of Construction Allied Trades and Technicians Zinc Development Association The following bodies were also represented in the drafting of the standar
7、d, through subcommittees and panels: Chartered Society of Designers Hevac Association Home Improvement Powder Coatings Association Amendments issued since publication Amd. No. Date CommentsBS4479-4:1990 BSI 04-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Def
8、initions 1 3 General 1 4 Spray coatings 1 5 Dip coatings 2 6 Powder coatings 3 7 Electrophoretic coatings 4 Appendix A Diagrams illustrating preferred and deprecated design featuresforarticles to be painted or varnished 5 Figure 1 Corners 5 Figure 2 Edges 5 Figure 3 Slots 5 Figure 4 Fins 5 Figure 5
9、Ribs 6 Figure 6 Indentations 6 Figure 7 Blind holes 6 Figure 8 Joints 6 Figure 9 Welds 7 Figure 10 Rivets 7 Figure 11 Drainage 7 Figure 12 Holding points 8 Figure 13 Hollow articles 8 Figure 14 Rolled and bend edges 8 Figure 15 Bends 9 Figure 16 Flat surfaces 9 Figure 17 Ideal box section: draining
10、and venting 9 Figure 18 Single box section: draining and access 10 Publications referred to Inside back coverBS4479-4:1990 ii BSI 04-1999 Foreword This Part of BS4479 has been prepared under the direction of the Pigments, Paints and Varnishes Standards Policy Committee and is based on a draft prepar
11、ed 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. This Part of BS4479 is one of a series of Parts which together form a revision of BS4479:1969. On publicatio
12、n of all the Parts, BS4479:1969 will be withdrawn. This revision of BS4479 comprises the following Parts: Part1: General recommendations; Part2: Recommendations for electroplated and autocatalytic coatings; Part3: Recommendations for conversion coatings; Part4: Recommendations for paint coatings and
13、 varnish coatings; Part5: Recommendations for anodic oxidation coatings; Part6: Recommendations for hot-dip metal coatings; Part7: Recommendations for thermally sprayed coatings; Part8: Recommendations for vitreous enamel coatings; Part9: Recommendations for low pressure and vacuum deposited coating
14、s. 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, intended to enhance or transform the surfaces of manufactured articles. However, time and money are often wasted becaus
15、e 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, when considering the overall costs and quality. This revision of BS4479 has been undertaken to extend the range
16、of coating processes covered. It is not intended to cover every conceivable design detail and every type of article or service condition. Adherence to the general principles described will, however, greatly assist in the achievement of the desired results. In any case of doubt or difficulty, special
17、ist 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 provide guidance towards good practice. A British Standard does not purport to include all the necessary prov
18、isions 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. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to10, an
19、 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 cover. 1) Institute of Metal Finishing.BS4479-4:1990 BSI 04-1999 1 1 Scope This Part of BS4479 gives rec
20、ommendations for the design of parts that are to be coated by painting or varnishing and covers four of the most commonly used methods whereby such coatings are applied, i.e.: a) spray coatings; b) dip coatings; c) powder coatings; d) electrophoretic coatings. This Part of BS4479 outlines the salien
21、t features of each method of application, and highlights the advantages and short-comings of each. Design considerations are clearly given for each of the four processes, and Annex A illustrates some preferred and deprecated design features. NOTE 1Reference is made throughout this Part of BS4479 to
22、paint coatings. For the purposes of this standard, the term paint may be taken to include varnish in cases where the latter may be also applied by the process described. NOTE 2In many instances a paint system is preceded by some other surface treatment, e.g.phosphated steel or chromated aluminium, a
23、nd the designer is directed to BS4479-3 which deals with conversion coating. NOTE 3It 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 necessarily referred to in each part. NOTE 4The
24、titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purpose of this Part of BS4479, the definitions given in BS2015 apply. 3 General Organic and inorganic paint finishes are applied to various articles in order to provide a decorative ef
25、fect or to protect the basic metal. In the construction, automotive and aircraft industries, for example, some articles cannot be easily or economically coated by other processes and hence painting by one means or another is the logical means of finishing. Whatever paint application process is used,
26、 it is essential that surfaces should be adequately prepared prior to paint application with due regard to the coating system and expected conditions of service. Attention is drawn to the provisions of BS7079. 4 Spray coatings 4.1 Process There are two main processes used in the spray coating of pai
27、nts: a) manual application (see4.2); b) electrostatic application (see4.3). 4.2 Manual spray coatings 4.2.1 General On new work spray painting is the most widely used method of applying paint finishes because of its speed of application and its adaptability to almost any condition, shape or size of
28、article. In addition to the conventional types of spray gun, there are adaptations of these guns for particular applications and finishes, allowing the design engineer greater freedom in his choice of designs. Extension spray heads, for example, are available for spraying the interior of small necke
29、d vessels, tubes, pipes, cylindrical objects, etc. These heads may give a disc spray, cone spray or fan spray, and may be directed at a45 or90 angle to the direction in which the gun is pointed. Inaccessible spots may be sprayed by using a head with which the spray is directed backwards at an angle
30、of25 or more. Airless spraying gives further application advantages in that it allows penetration into small crevices and sharp corners with less danger of dry spray. 4.2.2 Design considerations Despite the ability to spray awkward shapes by the various means described in4.2.1, it is still essential
31、 that the design engineer avoids certain shapes if at all possible. Access for maintenance should be considered at the design stage. The following principles should be observed. a) The design should ensure that all surfaces are fully accessible for surface preparation and should permit complete and
32、uniform application of the sprayed coating. b) Structures should be so designed that any focal points of corrosion are avoided from which further corrosion can spread. Major corrosive factors are moisture and dirt in which marine and industrial corrosive agents can collect and concentrate. The elimi
33、nation of all features that might facilitate lodgement or retention of moisture and dirt is, therefore, an important factor in the design.BS4479-4:1990 2 BSI 04-1999 c) Sharp edges should be avoided (see Figure 1 to Figure 3) by giving corners a minimum radius of1mm and smoothing out edges as much a
34、s possible. Fins and ribs should be spaced as widely as possible and edges made round and smooth (see Figure 4 and Figure 5). Corners and edges of indentations should be rounded to a radius of at least a quarter of their depth (see Figure 6). If blind holes are essential, they should be shallow with
35、 well rounded corners and edges (see Figure 7). d) The designer should aim to reduce the number of protruding fasteners, e.g.bolts and rivets, to a reasonable minimum. Welded joints are preferred as they aid shaping of optimal surfaces. Monolithic components are best, if practicable (see Figure 8).
36、e) Continuously welded joints facilitate the preparation of good surfaces for painting. Intermittent or spot welding should be avoided see Figure 9(a) and Figure 9(b). f) Butt-welded joints provide a better shape of surface than lap joints see Figure 9(c) and Figure 9(d). g) Countersunk rivets or sc
37、rews give a better surface profile than other types of corresponding fasteners (see Figure 10). h) Thorough finishing or smooth grinding of welds is extremely important in obtaining a good clean surface for painting. The removal of welding residue, flux, weld metal spatter, burrs, and other similar
38、surface defects prior to any type of overall surface cleaning should whenever possible be specified by the designer. NOTEMost high performance coatings are applied to blasted steel. Where the treatment of welds as described in itemh) is undertaken, reblasting of these areas is necessary before repri
39、ming. i) Pin holes in soldered (or welded) joints should be avoided in order to produce sound coatings. j) Methods of jointing likely to cause surface blemishes should be avoided, as these will either have to be removed or filled in at extra cost. k) Machining marks on surfaces should be minimized a
40、s far as possible. 4.3 Electrostatically applied spray coatings 4.3.1 General The application of coating materials to suitable articles by the electrostatic process has become increasingly important in industry, due mainly to the large paint savings made possible by the reduction of overspray and th
41、e ability of the electrostatic coating to “wrap” itself around the articles being sprayed. This is achieved by the paint material being electrically charged by various means and the article to be painted being earthed. The charged paint particles are attracted to the earth and “wrap” themselves even
42、ly around the earthed article. This characteristic of the process enables the backs and fronts of objects to be sprayed at the same time. 4.3.2 Design considerations The following principles should be observed. a) Generally the same principles apply as for the manual spray application. Electrostatic
43、 application has one major disadvantage, however, and that is its inability to coat adequately the inside surfaces of an article. This is because no electrostatic charge exists on the inside surfaces and hence no paint is attracted to it. Therefore, if the article has to be painted electrostatically
44、, the designer should avoid recesses and cavities. In some cases this will obviously not be possible, in which case an alternative paint application method should be used. b) If articles have to be sprayed electrostatically, the designer should avoid holes and slots on highly visible finished surfac
45、es. The electrostatic attraction produces a build-up of paint on the edges of such shapes, causing runs and sags. 5 Dip coatings 5.1 Process The simplest method of dip coating consists of lowering the article to be coated into a container of paint until it is submerged to the desired level, lifting
46、it out and hanging it over the container, or over drain areas, whilst the surplus paint drains off. There are, however, several inherent disadvantages with this particular method, which can be briefly summarized as follows. a) Due to the article shape, paint may be held in pockets or depressions, gi
47、ving rise to pools which do not drain properly. b) The article shape may give rise to runs and sags. c) “Fatty edges” (surplus paint along the edges) may form, together with tears at the corners.BS4479-4:1990 BSI 04-1999 3 d) Holes may be blocked and gaps and threads bridged. e) In enclosed sections
48、, refluxing (or solvent washing) may occur. f) The film thickness is always thicker at the bottom than at the top, due to drainage. For small items, a variation of dip painting which can be used is “tumbling” or barrel painting. In this, the articles to be painted are tumbled in a barrel, octagonal
49、or cylindrical in shape, and containing a small amount of paint until they are coated all over. They are then either tipped onto wire trays and stoved or, alternatively, the paint is drained out of the barrel and the articles are tumbled until they are dry. 5.2 Design considerations The main design criteria for parts to be dipped is that allowance should be made for maximum drainage. This can also be influenced by correct jigging of parts to be painted (see Figure 11) and by the correct positioning of holding points i
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