1、BRITISH STANDARD BS3900-F10: 1985 Cathodic disbonding (marine) Methods of test for paints Part F10: Determination of resistance to cathodic disbonding of coatings for use in marine environments It is recommended that this Part be read in conjunction with the general information in the Introduction t
2、o BS3900, issued separately. UDC667.637.233.3:667.636.22:620.197.527BS3900-F10:1985 This British Standard, having been prepared under the directionof the Pigments, Paintsand Varnishes StandardsCommittee, was published under the authority ofthe Board of BSI and comes intoeffect on 28 February1985 BSI
3、 04-1999 First published The Committees responsible forthis British Standard are shown inBS3900: Introduction. The following BSI references relate to the work on this standard: Committee reference PVC/10 Draft for comment82/55585DC ISBN 0 580 14167 5 Foreword This Part of BS3900 is one of a series o
4、f standards dealing with the sampling and testing of paints, varnishes and related products. It has been prepared under the direction of the Pigments, Paints and Varnishes Standards Committee. The method of test described in this Part permits the assessment of the ability of paint and other organic
5、coatings applied to metallic substrates to withstand cathodic disbonding. This method may also afford a basis for the comparison of particular coatings. The conditions of the test are more severe than those likely to be normally encountered and thus coating failure may be accelerated. It is recommen
6、ded that the test should be carried out for a period of at least26 weeks and hence this method is not suitable as a means of achieving quality control. In order to carry out the method of test described in this Part it is necessary for certain supplementary information, itemized in clause3, to be ma
7、de available or to be agreed between the parties. The procedure described in this Part is suitable for coatings to be used for the protection of ships and structures exposed to marine environments; it is based on the procedure developed and evaluated by COIPM (Comit International Permanent pour la P
8、rotection des Matriaux en Milieu Marin). The procedure described in Part F11 is based on that developed by the British Gas Corporation and should be used for coatings that are intended for the protection of land-based buried structures, such as pipelines. For coatings for application to sub-sea pipe
9、lines it may be necessary to consider either this Part or Part F11 or an alternative procedure; the method to be used should be subject to agreement by the parties. It has been assumed in the drafting of this British Standard that it will be used and applied by those who are appropriately qualified
10、and experienced. 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 do
11、cument comprises a front cover, an inside front cover, pages i and ii, pages1 to6, 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 the inside front cover. Amendments
12、issued since publication Amd. No. Date of issue CommentsBS3900-F10:1985 BSI 04-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Definitions 1 3 Supplementary information 1 4 Sampling 1 5 Electrolytes 1 6 Apparatus 1 7 Preparation of test specimens 3 8 Procedure 4 9 Test report 5 Appendix
13、 A Detection of accidental holidays 6 Figure 1 Potentiostatically-controlled cathodic protection circuit 2 Figure 2 Galvanostatically-controlled cathodic protection circuit 3 Publications referred to Inside back coverii blankBS 3900-F10:1985 BSI 04-1999 1 1 Scope This Part describes a method of test
14、 for determining the resistance to cathodic disbonding of a single coating or multi-coat system of paint, varnish or other organic coating applied to metallic substrates when the surface coating covering the metal substrate may contain or develop discontinuities. It is applicable to coatings that ar
15、e subjected to marine environments, such as those on ships or partially exposed marine structures. NOTE 1For coatings that are used to protect land-based metallic structures, the conditions of the test differ from those for coatings to be used in marine applications. BS3900-F11 describes a method su
16、itable for assessing coatings applied to buried structures. NOTE 2The test result may be influenced not only by the properties of the coating system under test, but also by the nature and preparation of the substrate, the method of application of the coating system and other factors. NOTE 3The title
17、s of the publications referred to in this standard are listed on the inside back page. 2 Definitions For the purposes of this British Standard, the definitions given in CP1021 and BS2015 apply, together with the following. cathodic disbonding the failure of adhesion between a coating and a metallic
18、surface that is directly attributable to cathodic protection conditions and that is often initiated by a defect in the coating system, such as accidental damage, imperfect application or excessive permeability of the coating 3 Supplementary information For any particular application, the following s
19、upplementary information shall be provided for this method of test. This information shall be derived, partly or totally, from the product specification, British Standard or other document for the product under test or, where appropriate, should be agreed between the parties. a) Material, dimensions
20、 and surface preparation of the test surface or substrate (see clause7). b) The nature of the coating and the environment for which the coating is intended. c) Method of application of the test coating to the substrate or test surface and its thickness. d) Duration and conditions of drying or curing
21、 of the coating (or conditions of stoving and ageing, if applicable) before testing. e) The specific method of measurement of the thickness of the dry coating, in micrometres, in accordance with BS3900-C5, and whether it is a single coating or a multi-coat system (see7.6). f) Duration of the test an
22、d any special conditions for testing (see8.3), including the electrolyte used (see clause5). g) Details of the preparation of the artificial holiday (see7.7). h) Whether the procedure for inspecting the test coating during and after testing should include assessment of loss of adhesion (see8.4.3). 4
23、 Sampling A representative sample of the product to be tested (or of each product in the case of a multi-coat system) shall be taken as described in BS3900-A1. Each sample shall be examined and prepared for testing as described in BS3900-A2. 5 Electrolytes 5.1 Natural sea water, fresh. If necessary,
24、 suspended solids may be removed by filtering through filter paper 1) . 5.2 Synthetic sea water 2) , prepared by dissolving23.0g of sodium chloride (NaCl),8.9g of sodium sulphate decahydrate (Na 2 SO 4 10 H 2 O),9.8g of magnesium chloride hexahydrate (MgCl 2 6H 2 O) and1.2g of anhydrous calcium chlo
25、ride (CaCl 2 ) in water and diluting the solution to 1L. The reagents used shall be of recognized analytical quality, and water complying with BS3978 shall be used. 6 Apparatus 6.1 Tank, of glass or other inert material that will not affect the pH of the electrolytes(5.1 or5.2). The tank shall have
26、a depth of not less than200mm and shall have one linear dimension (diameter or length) of not less than700mm (see8.2). A system for aerating the electrolyte shall be provided. 6.2 Anode, of graphite with a minimum length of200mm and a minimum diameter of15mm, or of platinum wire, platinum gauze or p
27、latinized titanium. The anode shall be at least10% longer than the major dimension of the test specimen (see7.2). 1) Whatman No.41 and No.541 filter papers have been found to be suitable. 2) This solution is in accordance with the synthetic sea water specified for the Armament Research Establishment
28、 (of the Ministry of Supply) salt droplet test described in clause8 of BS1391:1952.BS3900-F10:1985 2 BSI 04-1999 6.3 Reference electrode(s), preferably of the saturated calomel type, constructed from either glass or plastics with a porous plug. If other reference electrodes, e.g.Ag/AgCl, are used th
29、ese shall be checked against the standard calomel electrode and measured potentials shall be corrected in accordance with Table 4 in CP1021:1973. 6.4 Voltmeter, with minimum resistance of10M7, and capable of measuring in the range0V to2V to the nearest1mV. 6.5 Cathodic protection circuit, operating
30、from a d.c.supply and capable of maintaining the electrode potential of the test substrates (7.1) at1 000 5mV relative to the calomel reference electrode(6.3). The potential shall be controlled potentiostatically but if a potentiostat is not available a galvanostat may be used. The potential shall b
31、e frequently checked and adjusted to ensure that the electrode potential is within the specified limits (see8.3.3). NOTETypical cathodic protection circuits are shown in Figure 1 and Figure 2. Figure 1 Potentiostatically-controlled cathodic protection circuit (see 6.5)BS 3900-F10:1985 BSI 04-1999 3
32、7 Preparation of test specimens 7.1 Test substrates Test substrates shall be representative of the substrate to which the test coating is to be applied. If samples of the typical substrate are not available, test panels shall be used. The test panels shall be of steel and shall comply with the requi
33、rements of BS3900-A3. NOTEIt may be necessary for the surface finish of the panels to correspond to that of the typical substrate to be used see clause3 a). 7.2 Dimensions The minimum dimensions of each of the test substrates(7.1) shall be150mm 100mm 2mm, unless otherwise specified see clause3 a). 7
34、.3 Electrical connection Each test specimen shall have an insulated conductor, firmly attached to the substrate by a self-tapping screw or a small nut and bolt. NOTEIt may be convenient to attach the conductor after applying the coating to the substrate (see7.4). 7.4 Preparation and coating of the t
35、est substrates Either prepare and coat each substrate in accordance with the supplementary information given in the appropriate product standard or in the agreement between the parties (see clause3), or blast clean each test panel (see note to7.1) in accordance with BS3900-A3 and coat in accordance
36、with the manufacturers instructions for the product or system under test. Coat all surfaces, including the edges, of the test substrate with the product or system under test, unless otherwise specified. Protect any uncoated surfaces of the test substrate and the connection to the insulated conductor
37、 (see7.3) with a coating of paraffin wax, a solventless epoxy resin, or a resin consisting of approximately80% (m/m) beeswax and20%(m/m) colophony resin. Apply this latter resin at a temperature of about70C. Prepare and coat sufficient test specimens for each product or paint system to be tested in
38、triplicate. Also prepare, in triplicate, control specimens which are not to be connected to the cathodic protection system. Figure 2 Galvanostatically-controlled cathodic protection circuit (see 6.5)BS3900-F10:1985 4 BSI 04-1999 7.5 Drying and conditioning of the specimens Dry (or stove and age) the
39、 coated test and control specimens for the time and under the conditions specified for the product under test (see clause3). Unless otherwise specified, condition the specimens at23 2 C and at a relative humidity of50 5% for a minimum of16h, with free circulation of air. Do not expose them to direct
40、 sunlight. Carry out the determination of the coating thickness (see7.6), formation of the artificial holiday (see7.7) and the test procedure (see clause8) as soon as possible after completion of conditioning see clause3 d). 7.6 Thickness of the coating Determine the thickness, in micrometres, of th
41、e dry coating on each test and control specimen in accordance with BS3900-C5 see clause3 e). 7.7 Artificial holiday Immediately before carrying out the test, prepare an artificial holiday on a coated surface of each of the specimens. Unless otherwise specified see clause3 g), prepare the holiday by
42、placing a mask with a cut-out hole of 10 1mm diameter on the surface and abrasive blast-cleaning the specimen until the coating has been completely removed from the exposed area. Centre the artificial holiday not less than30mm from any edge of a specimen. Use chilled iron grit complying with grade G
43、17 or G24 of BS2451. NOTEPreparation of the holiday by the use of masking tape fixed to the substrate before coating is not recommended as, after removal of the tape, the presence of residual adhesive on the surface can invalidate the test. Check that an electrical connection exists between the holi
44、day and the conductor (see7.3). 7.8 Accidental holidays Test the coating on each specimen for freedom from accidental holidays as described in Appendix A. 8 Procedure 8.1 Determinations Carry out the procedure on three test specimens for each test coating. 8.2 Arrangement of the test specimens in th
45、e tank 8.2.1 Place the anode(6.2) in the centre of the tank(6.1) and connect it to the positive terminal of the cathodic protection circuit(6.5). Locate the prepared specimens (see clause7) and, if space permits (see8.2.2), the control specimens in racks in the tank and adjust their position such th
46、at each specimen is not less than300mm from the anode(6.2) in the tank, is not less than50mm from the base and will be totally immersed when the tank is filled with the electrolyte. Ensure that no specimen is touching another and that no specimen is in contact with the sides of the tank. Ensure also
47、 that no panel face containing a holiday is shielded from the anode by any obstruction or by another specimen, and that the flow of electrolyte around and between the specimens is not impeded. Connect each test specimen to the negative terminal of the cathodic protection circuit by means of the insu
48、lated conductor (see7.3), but leave the control specimens unconnected. 8.2.2 If space is not available, place the control specimens in an equivalent tank without the anode and cathodic protection circuit, and state this in the test report. 8.3 Conditions 8.3.1 Fill the tank to a minimum depth of200m
49、m with the electrolyte (5.1 or5.2). Commence aeration and check that the electrolyte is at23 2 C. If the electrolyte used is natural sea water(5.1) and it is not feasible to adjust its temperature to23 2 C monitor the temperature of the electrolyte in the tank at regular intervals and record the readings in the test report. Locate the calomel reference electrode or electrodes(6.3) in the vicinity of the test specimens but not shielding a holiday. Ensure that no electrode is less than300mm from the anode. 8.3.2 Maintain a continual flow of the
