1、BRITISH STANDARD CONFIRMED OCTOBER1984 BS3900-F6: 1976 Natural weathering Methods of test for paints Part F6: Notes for guidance on the conduct of natural weathering tests It is recommended that this Part be read in conjunction with the general information in the Introduction to BS3900 issued separa
2、tely (revised edition published March 1969). UDC667.613.2:620.193.2BS3900-F6:1976 BSI 04-1999 ISBN0 580 09391 3 Foreword This edition of BS3900-F6, which replaces the first edition published in1972, is technically identical with International Standard ISO2810 “Paints and varnishes Notes for guidance
3、 on the conduct of natural weathering tests”. 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 obligati
4、ons. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1to7 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 inside front cover. Amend
5、ments issued since publication Amd. No. Date CommentsBS3900-F6:1976 BSI 04-1999 i Contents Page Foreword Inside front cover 1 Scope and field of application 1 2 References 1 3 Supplementary information 1 4 General 1 5 Preparation of test specimens 2 6 Exposure racks 2 7 Procedure 3 8 Test report 3 A
6、ppendix A Information on exposure sites 4 Figure 1 Suitable method of mounting panels 6 Figure 2 Apparatus for high acidity method 7 Figure 3 Apparatus for Ambler method 7 Figure 4 Apparatus for Irsid method 7ii blankBS3900-F6:1976 BSI 04-1999 1 1 Scope and field of application This Part specifies t
7、he factors which need to be taken into consideration in the selection of methods for the exposure to natural weathering of paint films or systems for the purpose of evaluating their durability. As far as possible, a method is specified which is recommended for use where no specialized requirements a
8、pply. NOTEThe appendix gives information on the characterization of exposure sites. 2 References This Part makes reference to other parts of BS3900 as follows: 3 Supplementary information When natural weathering tests are carried out, the following supplementary information shall be supplied. This i
9、nformation shall be derived from the national standard or other document for the product under test or, where appropriate, shall be the subject of agreement between the interested parties. a) Material and thickness of substrate. b) Method of preparation of substrate and method of application of the
10、test coating. c) Thickness of coating, in micrometres, whether it is to be a single coating or a multicoat system, and whether both sides of the specimen are to be coated with the product under test. d) Conditions of drying of coated test specimen (orconditions of stoving and ageing, if appropriate)
11、, intervals between coats and period of conditioning before exposure. e) Whether bare areas are to be provided on the specimen and if so, their size and position and by what means they are to be made. f) Details of any periodic washing or polishing procedure to be carried out during the course of ex
12、posure. g) Any particular requirements regarding the location of the exposure. h) The duration of the test and which characteristics of the product under test are to be considered in evaluation of its performance and, where requested, the method of removal of the coating from the substrate. 4 Genera
13、l 4.1 Durability can be defined as the degree to which paint films or systems withstand the destructive effect of the conditions to which they are exposed. It is influenced by the manner, place and season in which the paint is exposed, and these factors must be given due consideration in selecting a
14、 test procedure appropriate to the proposed end-use of the product under test. 4.2 In particular, the factors to be considered include the following. a) Location of the exposure site, for example, industrial, marine, rural etc. In choosing sites, local gross influences on the general level of pollut
15、ion shall be avoided, unless they are appropriate to the proposed end-use of the product under test. b) Height, angle and aspect of exposure rack. These factors will govern the extent to which the specimens are affected by dew, frost, atmospheric pollutantsetc. c) The nature of the terrain on which
16、the rack is constructed (for example concrete, grass, graveletc.). This may well affect the climatic conditions around the specimen under test. It would rarely be feasible to select an ideal terrain in practice, but the effect of any such variations will be minimized by ensuring that all specimens a
17、re situated sufficiently above the ground to avoid any interference (see 6.5). d) Whether the performance of the paint on the face or the back of the specimen is of greater interest. Certain types of breakdown, for example corrosion and mould growth, are frequently more severe on the sheltered parts
18、 of the specimen. e) The end-use of the material, including its substrate and whether the film is to be washed or polished in service. 4.3 The results of tests on an exposure rack will refer precisely only to the environment in which products were tested although, in practice, products will generall
19、y be used under a wide range of natural conditions. Provided that the test conditions are reasonably appropriate to the proposed end-use however, the relative performance of a number of products tested at the same time will enable valid deductions to be drawn. It is therefore desirable that a series
20、 of specimens for evaluation shall include one or more products of known performance to act as a standard of comparison. PartA3 Standard panels for paint testing PartC5 Determination of film thicknessBS3900-F6:1976 2 BSI 04-1999 4.4 The results of exposure tests may vary according to the time of yea
21、r during which the tests are carried out, although the effect will be minimized if the exposure period is sufficiently long to “average out” any variations. It may be necessary in the case of exposure periods of less than a year, to carry out further tests, say six months later, if full characteriza
22、tion of the product is to be achieved. 4.5 Although the normal practice is to carry out exposure tests for a fixed period of time it may be preferable in certain circumstances, particularly for the determination of certain optical characteristics, to define the test period in terms of the quality an
23、d quantity of solar radiation to which the specimen is to be subjected. This procedure may in part overcome the seasonal variations referred to in 4.4. 4.6 Care is required in the selection of test specimens of variable substrates, for example wood or weathered steel, and in these cases replication
24、of the tests is essential if misleading results are to be avoided. 4.7 Washing and polishing will vary different aspects of durability and results obtained using these procedures shall be interpreted with caution unless the treatment is appropriate to the end-use of the product. 5 Preparation of tes
25、t specimens 5.1 The simplest and most widely used test specimen is a flat panel of the appropriate substrate, but much useful additional information may be obtained by carrying out exposure tests on structures. This is particularly so on wooden assemblies such as window frames, where paint performan
26、ce at the joints is of interest. Design features which allow entrapment of water may also lead to premature paint failure, and assessment of performance under these conditions would normally involve the use of test specimens which closely reproduce the features of interest. 5.2 Unless otherwise stat
27、ed, use an appropriate panel complying with and prepared in accordance with BS3900-A3. In no case shall the area of the panel be less than0.03m 2and no side shall be less than100mm. 5.3 Coat the specimen with the product(s) under test by the appropriate method and dry (or stove and age) each coat in
28、 the specified manner for the specified time. If normal drying conditions are specified these shall be interpreted as a temperature of23 2 C, a relative humidity of50 5 % and free circulation of air, with the specimen in a vertical position and not exposed to direct sunlight. 5.4 It is generally pre
29、ferred that both faces and the edges of test panels be coated with the product under test, unless it would not be so used in practice. Alternatively, the back and edges may be coated with a good-quality protective paint see 4.2 d). 5.5 If specified, particularly in the case of corrosion tests, provi
30、de uncoated areas on the specimen preferably by one or more of the following methods. 5.5.1 After the specified drying time and immediately before placing the specimens on the exposure rack, make a scratch in the paint film, so as to expose the substrate. The scratch shall be made with a steel scrib
31、er, between0.5mm and1mm in width and ground to a chisel edge. 5.5.2 Before applying the product(s) under test, attach to the prepared specimen a strip of self-adhesive masking tape of agreed size and location. Coat the specimen in the normal way. After the specified drying time, and immediately befo
32、re placing the specimen on the exposure rack, remove the masking tape. Clean off any residues of adhesive with a suitable solvent which does not affect the paint. 5.5.3 In the case of a standard test panel, coat the face or faces with the product under test, but leave the edges bare. 5.6 Determine t
33、he film thickness using one of the methods described in BS3900-C5. 6 Exposure racks 6.1 Exposure racks shall usually support the panels at an angle of45 to the horizontal and facing toward the equator. In special circumstances, for example, the testing of textured wall finishes, vertical exposure ma
34、y be preferred. By agreement other exposure angles or orientations may be adopted. 6.2 The racks shall be so situated that the specimens are not protected or overshadowed by neighbouring objects. 6.3 The construction of the racks shall be such that the backs of the specimens are freely exposed to th
35、e atmosphere and such that water drainage does not occur from one panel to another. 6.4 Specimens shall not be in electrical contact with metals during the exposure period, nor as far as possible in direct contact with wood or other porous material. A suitable method of mounting panels is shown in F
36、igure 1. If panels are supported in grooves, suitable drainage holes shall be provided to prevent accumulation of water.BS3900-F6:1976 BSI 04-1999 3 6.5 Unless otherwise stated, the racks shall be so constructed that all specimens are supported not less than 1 m above the level of the site. This wil
37、l minimize interference due to the nature of the terrain see 4.2 c) or from tall vegetation on infrequently visited sites, and will avoid the possibility of contamination from splashing during heavy rainfall. 7 Procedure 7.1 After the specified conditioning time expose the specimen on the rack for t
38、he specified time (see 4.4 and 4.5). 7.2 If specified, wash the whole or part of the specimen at the required intervals. It is preferable to wash a strip on the right or left of the panel face, rather than the top or bottom, although there may be reasons for defining the particular area selected. Wh
39、ere no specialized, washing procedure is required, it has been found suitable to use distilled water, containing0.5% of a neutral wetting agent. The solution may be applied with a soft brush, finally rinsing the surface thoroughly with distilled water. 7.3 If specified, wash as described in 7.2 and
40、polish the whole or part of the specimen at the required intervals, using the specified polish. 7.4 Examine the test specimen at intervals, separately noting effects on front, back, edges or bare areas as appropriate. Examinations shall be at intervals appropriate to the rate of breakdown for change
41、 of colour, loss of gloss, blistering etc. of the paint film and for signs of corrosion of the substrate. Also examine at a magnification of about 25 for checking, cracking, blistering etc. of the paint film and for signs of. corrosion of the substrate. Examine for signs of chalking by wiping a smal
42、l area of the surface with a piece of velvet of contrasting colour. 7.5 After the specified period of exposure, carry out a final examination of the coating. If it is required to examine the substrate for signs of attack, remove the coating by the specified method. 8 Test report The test report shal
43、l include the following information. a) A reference to this British Standard. b) Type and identification of the product under test. c) The items of supplementary information referred to in clause3. d) The British Standard or other document supplying the information referred to inc). e) Any deviation
44、 from the agreed test procedure. f) The results of the test in terms of the stated requirements. g) Site and period of exposure and the date of its commencement. The test report should also preferably contain, wherever possible, data concerning exposure conditions as given in Appendix A.BS3900-F6:19
45、76 4 BSI 04-1999 Appendix A Information on exposure sites A.1 Definition of climatic and environmental parameters of exposure sites. Natural climatic data as well as the various sources of pollution should be qualitatively and quantitatively defined. A.1.1 Climatic data. The nature of the climate sh
46、ould where possible be defined in terms of the following classification and the altitude above sea level should also be stated. NOTEIt is not possible to cover all climates using a reasonably simple scheme and where climates occur which do not fit into the following scheme special reference to them
47、should be made. A.1.1.1 Humid tropical climates (mean temperature of coldest month above 18 C and a relative humidity above75% for a substantial part of the year) a) tropical climate without dry season; b) tropical climate with dry season. A.1.1.2 Tropical climates (mean temperature of coldest month
48、 above18C and a relative humidity below75% for a substantial part of the year). A.1.1.3 Very dry climates (conditions not permitting the growth of trees) a) steppe climate; b) desert climate. A.1.1.4 Warm temperate climates (mean temperature of coldest month between3C and18C) a) warm temperate clima
49、te without dry season; b) warm temperate climate with dry summer (Mediterranean climate); c) warm temperate climate with dry winter. A.1.1.5 Cold temperate climates (mean temperature of coldest month below3C and of warmest month above10C) a) cold temperate climate without dry season; b) cold temperate climate with dry winter. A.1.1.6 Polar climates (mean temperature of warmest month below10C) a) tundra climate (mean temperature of warmest month above0C); b) permafrost climate (mean temperature of warmest month below0C). A.1.1.7 High mountain climates
