1、BRITISH STANDARD BS4842:1984 Incorporating Amendment No.1 Specification for Liquid organic coatings for application to aluminium alloy extrusions, sheet and preformed sections for external architectural purposes, and for the finish on aluminium alloy extrusions, sheet and preformed sections coated w
2、ith liquid organic coatings UDC667.663.2-404+667.653:669.715-41/-42:721.011.6BS4842:1984 This British Standard, having been prepared under the directionof the Pigments, Paintsand Varnishes Standards Committee, was published underthe authority of the Board ofBSI and comes into effect on 31 August 198
3、4 BSI06-1999 First published December 1972 First revision August 1984 The following BSI references relate to the work on this standard: Committee reference PVC/25 Draft for comment82/52956 DC ISBN 0 580 13849 6 Committees responsible for this British Standard The preparation of this British Standard
4、 was entrusted by the Pigments, Paints and Varnishes Standards Committee (PVC/-) to Technical Committee PVC/25 upon which the following bodies were represented: Aluminium Coatings Association Aluminium Federation Aluminium Window Association British Institute of Interior Design Department of the Env
5、ironment (Building Research Establishment) Greater London Council HEVAC Association Home Improvement Powder Coatings Association Oil and Colour Chemists Association Paintmakers Association of Great Britain Ltd. Royal Institute of British Architects Steel Window Association Amendments issued since pu
6、blication Amd. No. Date of issue Comments 7181 July 1992 Indicated by a sideline in the marginBS4842:1984 BSI 06-1999 i Contents Page Committees responsible Inside front cover Foreword ii Section 1. General 1 Scope 1 2 Definitions 1 Section 2. Performance and other requirements for liquid organic co
7、atings 3 Sampling of liquid organic coatings 1 4 Performance requirements for liquid organic coatings 1 5 Manufacturers certificate 3 6 Identification of liquid organic coatings 3 Section 3. Performance and other requirements for the finish on aluminium alloy extrusions, sheet and preformed sections
8、 coated with liquid organic coatings 7 Coating 3 8 Pre-treatment of aluminium alloy extrusions, sheet or preformed sections 3 9 Sampling of coated panels, extrusions, sheet and preformed sections 4 10 Performance requirements for the finish on coated aluminium extrusions, sheet and preformed section
9、s 4 11 Applicators certificate 5 12 Identification, care and maintenance 5 Section 4. Methods of test for liquid organic coatings applied to and finishes on aluminium alloy test panels, extrusions, sheet or preformed sections 13 Preparation of coated test panels 5 14 Resistance to mortar 5 15 Solven
10、t test 6 16 Resistance to acetic acid/salt spray 6 17 Permeability of coating and quality of pre-treatment of the metal surface 7 Appendix A The care of the finish on coated aluminium alloy components for architectural purposes 8 Appendix B The maintenance of the finish on coated aluminium alloy com
11、ponents installed externally 8 Publications referred to 10BS4842:1984 ii BSI 06-1999 Foreword This British Standard has been revised under the direction of the Pigments, Paints and Varnishes Standards Committee at the request of the Aluminium Window Association. This edition of the standard supersed
12、es BS4842:1972, which is withdrawn. Aluminium alloy windows are frequently located in relatively inaccessible locations and BS4842 was first published in1972 as the direct result of the need to ensure that coatings applied to aluminium components (and especially to aluminium windows) have a satisfac
13、tory service life with low maintenance requirements. The complete revision of the standard was undertaken to accommodate comments from industry, particularly with regard to some of the performance tests which were too prolonged, to accommodate acknowledged improvements in the properties of coating p
14、roducts and also to incorporate powder coating finishes which had been developed since the first edition. Technical considerations indicated that liquid coatings and finishes and powder coatings and finishes required different performance test procedures and therefore separate standards have been pr
15、epared for each. This edition of BS4842 deals with liquid organic coatings for and finishes on aluminium alloy components; BS6496 deals similarly with powder organic coatings for and finishes on aluminium alloy components. This standard relates to two different interfaces (between coating manufactur
16、er and coating applicator and between applicator and, for example, architect) and has therefore been divided into sections in such a way that compliance can be claimed with the appropriate section. In order to assist in identifying these two interfaces, the term “coating” has been used consistently
17、in section 2 to describe the liquid organic coating when applied to the test panels, and the term “finish” has been used in section 3 when referring to the liquid organic coating as applied by the applicator. Section 2 of this standard gives the requirements for the organic coatings to be applied to
18、 aluminium alloy components and the tests described therein are intended to be carried out by the coating manufacturer. Section 3 gives the requirements for the finish on extrusions, sheet and preformed sections of aluminium alloy and the tests described therein are intended to be carried out by the
19、 coating applicator. Some coatings containing metallic pigments and certain coatings with gloss levels below50units may not comply with all the requirements of section 2 of this standard. It is stressed that preparation and pre-treatment of the metal surface are very important in producing satisfact
20、ory finishes on aluminium. Therefore, to ensure optimum adhesion, a preliminary chemical conversion of the aluminium surface has been made a requirement of section 3 of this standard except when the organic coating is to be applied by anodic electrophoresis. Indeed, preparation and pre-treatment of
21、the surface are so important that the inclusion of a rapid, routine test to detect faulty processing was considered essential, even though none of the tests available could test the pre-treatment processes independently of other parameters. Thus a test to assess the quality of pre-treatment is speci
22、fied in10.9, although failure in this test does not necessarily imply that faulty pre-treatment is the only cause. This test has been specifically introduced as it is an accelerated procedure which reveals when the pre-treatment conditions are becoming unsatisfactory. This same test is also specifie
23、d in4.12 as a means of assessing the permeability of the coating.BS4842:1984 BSI 06-1999 iii It was considered essential to section 2 of this standard that there should be a performance test to assess the resistance to weathering of organic coatings. It was also desirable that this test should inclu
24、de the assessment of permissible loss in gloss. While there were merits in having an accelerated procedure see4.9 a) which allows a coating to be assessed within about12weeks, evidence was cited which showed that the loss of gloss after that period could be more severe than that observed under pract
25、ical conditions. Moreover the converse had also been observed. Thus the decline in gloss could not be considered an exact measure of potential performance and this prevented the property being used in the assessment of a coating. An alternative procedure see4.9 b) was proposed to overcome this probl
26、em, despite the disadvantage of a test period of1 year. However, while this test was more akin to practical conditions and generally more reliable, again the loss of gloss experienced could not be correlated with performance. It is for this reason that both tests in this specification include an eva
27、luation of coatings for their resistance to chalking to partially resolve the difficulty. Each of the weathering tests is believed to have value but also has disadvantages, and hence the Technical Committee responsible for preparing this standard concluded that both should be included. The artificia
28、l weathering test is for use routinely but in the event of a dispute, the product is required to satisfy the appropriate requirements after undergoing both that and the natural weathering test. It is important that the finish on architectural components should be compatible with sealing compounds us
29、ed in the building industry. In general, finishes which comply with section 3 of this standard will satisfy this requirement but, in cases of doubt, the user should satisfy himself that the particular sealant he intends to use is compatible with and adheres to the finish by referring the matter to t
30、he sealant supplier. It has been assumed in the drafting of this British Standard that the test methods will be applied by those who are appropriately qualified and experienced. Certification. Attention is drawn to the certification facilities offered by BSI described on the inside back cover of thi
31、s standard. 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. Summary of pages This documen
32、t comprises a front cover, an inside front cover, pagesito iv, pages1to10, 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 cover.iv blankBS4842:1984 B
33、SI 06-1999 1 Section 1. General 1 Scope Section2 of BS4842 specifies requirements for liquid organic coatings which are intended for application to aluminium alloy extrusions, sheet and preformed sections that are not to be further formed (except for cutting). Section3 of BS4842 specifies requiremen
34、ts for the finish on aluminium alloy extrusions, sheet and preformed sections when so coated. The methods of test for these coatings and finishes are described in section4. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purp
35、oses of this British Standard, the definitions given in BS2015 apply together with the following. 2.1 finish 1) the final or only coat in a painting process 2.2 conversion coating a modification to an aluminium surface by chemical treatment with chromate ions or chromate and phosphate ions without t
36、he use of an applied electric current 2.3 test piece a single item which is representative of the work being processed 2.4 test sample a group of test pieces 2.5 significant surface that part of the total surface of the finish on which a particular requirement for the specified finish is to be asses
37、sed 2.6 specifier the person issuing a contract specifying particular properties of a liquid organic coating before or after its application to a substrate Section 2. Performance and other requirements for liquid organic coatings NOTEThe tests associated with these requirements are intended to be ca
38、rried out by or on behalf of the supplier or manufacturer of a liquid organic coating. 3 Sampling of liquid organic coatings A representative sample of the liquid organic coating shall be taken as described in BS3900-A1. The sample shall be examined and prepared for testing by the appropriate method
39、s described in BS3900-A2. 4 Performance requirements for liquid organic coatings 4.1 General. The tests shall be carried out in duplicate. The test panels referred to in this clause shall be prepared as described in clause13. The coating, when applied to a prepared test panel, shall show no scratche
40、s through to the substrate. When a coated test panel is illuminated as described in BS3900-D1 and examined at an oblique angle with normal or corrected vision, no blisters, craters, pinholes, scratches, flow lines, streaks or tears shall be visible from a distance of about0.5m. 4.2 Colour. When a co
41、ated test panel is examined by the procedure described in BS3900-D1, the colour of the coating shall match (see BS2015) the reference colour previously nominated by the specifier. NOTEColours should be chosen from BS4800 but when this is not possible the colour of a reference sample should be agreed
42、. 4.3 Gloss. When a coated test panel is tested by the procedure described in BS3900-D5, using incident light at60 to the normal to the surface of the coating, the gloss level of the coating shall be within five units of the value previously nominated by the specifier. 4.4 Adhesion. When a coated te
43、st panel is tested by the procedure described in BS3900-E6 using a spacing of1mm between each of the six parallel cuts, the result shall be in accordance with classification0 of that standard. When a piece of adhesive tape 2) , approximately25mm 150mm, is applied firmly to the cut area and then remo
44、ved rapidly by pulling at right angles to the test panel, no pieces of coating other than debris from the cutting operation shall be removed from the surface of the coating. 1) This definition differs from that given in BS2015 which is currently being revised. 2) Sellotape type1101 has been found to
45、 be suitable.BS4842:1984 2 BSI 06-1999 4.5 Scratch resistance. When a coated test panel is tested by the procedure described in BS3900-E2 using a load of2000g on a tungsten-carbide ball of1mm diameter, there shall be no penetration through the coating to the substrate. 4.6 Resistance to mortar. When
46、 a coated test panel is tested by the procedure described in clause14, the mortar shall be readily dislodged without the use of an implement. There shall be no detachment of the coating and no change in its appearance. 4.7 Solvent test for cure. When a coated test panel is tested by the procedure de
47、scribed in clause15, the gloss of the coating shall not be reduced by more than five units from the initial gloss (see4.3) and there shall be no transfer of the coating to the cotton wool pad. 4.8 Resistance to acetic acid/salt spray. When a coated test panel is tested by the procedure described in
48、clause16 for a period of1000h, there shall be no blistering, softening or detachment of the coating. There shall be not more than2.0mm of corrosion creep from the scored line, measured at right angles to the line, and the remainder of the substrate shall show no signs of corrosion. When, after the p
49、anel has been washed with water and allowed to dry for24h at23 2 C, a piece of adhesive tape 3) , approximately25mm 150mm, is applied firmly to the cut area and then removed rapidly by pulling at right angles to the test panel, no coating shall be removed from the surface of the panel unless it is within2.0mm of the scored line. 4.9 Weathering tests. Either the test given in a) or the test given in b) shall be carried out except in the case of a dispute, where the coating shall satisfy the given requirements after undergoing both tests (seeforeword and clause5). NOTENa
