《BS-7479-1991.pdf》由会员分享,可在线阅读,更多相关《BS-7479-1991.pdf(14页珍藏版)》请在三一文库上搜索。
1、BRITISH STANDARD BS 7479:1991 ISO 9227:1990 Method for Salt spray corrosion tests in artificial atmospheres BS 7479:1991 This British Standard, having been prepared under the direction of the Iron and Steel and Non-ferrous Metals Standards Policy Committees, was published under the authority of the
2、Standards Board and comes into effect on 20 December 1991 BSI 01-1999 The following BSI references relate to the work on this standard: Committee reference ISM/NFM/8 Draft for comment 87/44660 DC ISBN 0 580 19998 3 Committees responsible for this British Standard The preparation of this British Stan
3、dard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) and Non-ferrous Metals Standards Policy Committee (NFM/-) to Technical Committee ISM/NFM/8, upon which the following bodies were represented: Aluminium Federation British Gas plc British Steel Industry Department of Trade an
4、d Industry (National Physical Laboratory) Department of Transport (Transport and Road Research Laboratory) Electricity Industry in United Kingdom Institute of Corrosion Institution of Structural Engineers Society of Chemical Industry United Kingdom Atomic Energy Authority The Welding Institute Amend
5、ments issued since publication Amd. No.DateComments BS 7479:1991 BSI 01-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Normative references1 3Test solutions1 4Apparatus2 5Method of evaluation of the corrosivity of the chamber3 6Test specimens4 7Arrangement
6、of the test specimens4 8Operating conditions5 9Duration of tests5 10Treatment of specimens after test5 11Evaluation of results5 12Test report6 Annex A (informative) Schematic diagram of one possible design of spray cabinet7 Annex B (informative) Bibliography8 Publication(s) referred toInside back co
7、ver BS 7479:1991 ii BSI 01-1999 National foreword This British Standard has been prepared under the direction of the Iron and Steel and Non-ferrous Metals Standards Policy Committees. It is identical with ISO 9227:1990 “Corrosion tests in artificial atmospheres Salt spray tests” published by the Int
8、ernational Organization for Standardization (ISO). This British Standard supersedes BS 5466-1:1977, BS 5466-2:1977 and BS 5466-3:1977, which are withdrawn. NOTETypographical error. In footnote4) of clause 5.1.1 “faultness” should read “faultless”. The Technical Committee has reviewed the provisions
9、of ISO 1462, ISO 3574 and ISO 6372-1, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for
10、their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International standardCorresponding British Standard ISO 4540:1980BS 5466 Methods for corrosion testing of metallic coatings Part 6:1982 Rating of results of corr
11、osion tests on electroplated coatings cathodic to the substrate (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendme
12、nts incorporated. This will be indicated in the amendment table on the inside front cover. ISO 9227:1990(E) BSI 01-19991 1 Scope This International Standard specifies the apparatus, the reagents and the procedure to be used in conducting the neutral salt spray (NSS), acetic acid salt spray (AASS) an
13、d copper-accelerated acetic acid salt spray (CASS) tests for assessment of the corrosion resistance of metallic materials with or without permanent corrosion protection or temporary corrosion protection. It also describes the method employed to evaluate the corrosivity of the test cabinet environmen
14、t. It does not specify the dimensions of test specimens, the exposure period to be used for a particular product, or the interpretation of results. Such details are provided in the appropriate product specifications. The salt spray tests are particularly useful for detecting discontinuities such as
15、pores and other defects in certain metallic, anodic oxide and conversion coatings. The neutral salt spray test applies to metals and their alloys; certain metallic coatings (anodic and cathodic)1); certain conversion coatings1); certain anodic oxide coatings1); organic coatings on metallic materials
16、. The acetic acid salt spray test is especially useful for testing decorative coatings of copper + nickel + chromium or nickel + chromium. It has also been found suitable for testing anodic oxide coatings on aluminium. The copper-accelerated acetic acid salt spray test is useful for testing decorati
17、ve coatings of copper + nickel + chromium or nickel + chromium; it has also been found suitable for testing anodic coatings on aluminium.2) 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. A
18、t the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and
19、ISO maintain registers of currently valid International Standards. ISO 1462:1973, Metallic coatings Coatings other than those anodic to the basis metal Accelerated corrosion tests Method for the evaluation of the results. ISO 3574:1986, Cold-reduced carbon steel sheet of commercial and drawing quali
20、ties. ISO 4540:1980, Metallic coatings Coatings cathodic to the substrate Rating of electroplated test specimens subjected to corrosion tests. ISO 6372-1:1989, Nickel and nickel alloys Terms and definitions Part 1: Materials. 3 Test solutions 3.1 Preparation of the sodium chloride solution Dissolve
21、a sufficient mass of sodium chloride in distilled or deionized water with a conductivity not higher than 20 S/cm at 25 C 2 C to produce a concentration of 50 g/l 5 g/l. The sodium chloride concentration of the sprayed solution collected shall be 50 g/l 5 g/l. The specific gravity range for a 50 g/l
22、5 g/l solution is 1,025 5 to 1,040 0 at 25 C. The sodium chloride shall contain less than 0,001 % (m/m) of copper and less than 0,001 % (m/m) of nickel as determined by atomic absorption spectrophotometry or another analytical method of similar sensitivity. It shall not contain more than 0,1 % (m/m)
23、 of sodium iodide or more than 0,5 % (m/m) of total impurities calculated for dry salt. NOTE 1If the pH of the prepared solution, measured at 25 C 2 C, is outside the range 6,0 to 7,0, investigate the presence of undesirable impurities in the salt and/or the water. 3.2 pH adjustment Adjust the pH of
24、 the salt solution to the desired value on the basis of the pH of the sprayed solution collected. 3.2.1 NSS test Adjust the pH of the salt solution (3.1) so that the pH of the sprayed solution collected within the test cabinet (4.1) is between 6,5 to 7,2. Check the pH using electrometric measurement
25、 at 25 C 2 C, or, in routine checks, with a short-range pH paper which can be read in increments of 0,3 pH units or less. Make any necessary correction by adding hydrochloric acid or sodium hydroxide solution of analytical grade. 1) See annex B. 2) Attention is drawn to the fact that no satisfactory
26、 basis for comparison can be derived from this test with regard to the respective quality of nickel + chromium coatings and copper + nickel + chromium coatings, because the reagent used contains a copper ion which promotes corrosion in the presence of nickel but is without influence on copper. ISO 9
27、227:1990(E) 2 BSI 01-1999 Possible changes in pH may result from loss of carbon dioxide from the solution when it is sprayed. Such changes may be avoided by reducing the carbon dioxide content of the solution by, for example, heating it to a temperature above 35 C before it is placed in the apparatu
28、s, or by making the solution from freshly boiled water. 3.2.2 AASS test Add a sufficient amount of glacial acetic acid to the salt solution (3.1) to ensure that the pH of samples of sprayed solution collected in the test cabinet (4.1) is between 3,1 and 3,3. If the pH of the solution as initially pr
29、epared is 3,0 to 3,1, the pH of the sprayed solution is likely to be within the specified limits. Check the pH using electrometric measurement at 25 C 2 C, or, in routine checks, with a short-range pH paper which can be read in increments of 0,1 pH units or less. Make any necessary correction by add
30、ing glacial acetic acid or sodium hydroxide of analytical grade. 3.2.3 CASS test Dissolve a sufficient mass of copper(II) chloride dihydrate (CuCl22H2O) in the salt solution (3.1) to produce a concentration of 0,26 g/l 0,02 g/l equivalent to (0,205 0,015) g of CuCl2 per litre. Adjust the pH using th
31、e procedures described in 3.2.2. 3.3 Filtration If necessary, filter the solution before placing it in the reservoir of the apparatus, to remove any solid matter which might block the apertures of the spraying device. 4 Apparatus All components in contact with the spray or the test solution shall be
32、 made of, or lined with, materials resistant to corrosion by the sprayed solution and which do not influence the corrosivity of the sprayed test solutions. The apparatus shall include the following components. 4.1 Spray cabinet The cabinet shall have a capacity of not less than 0,2 m3 and preferably
33、 of not less than 0,4 m3 since, with smaller volumes, difficulties were experienced in ensuring the even distribution of spray. For large-capacity cabinets, it is necessary to ensure that the conditions of homogeneity and distribution of the spray are met. The upper parts of the cabinet shall be des
34、igned so that drops of sprayed solution formed on its surface do not fall on the specimens being tested. The size and shape of the cabinet shall be such that the collection rate of solution in the cabinet is within the limits specified in 8.2. NOTE 2A schematic diagram of one possible design of spra
35、y cabinet is shown in annex A. 4.2 Heater and temperature control An appropriate system maintains the cabinet and its contents at the specified temperature (see 8.1). The temperature shall be measured at least 100 mm from the walls. 4.3 Spraying device The device for spraying the salt solution compr
36、ises a supply of clean air, of controlled pressure and humidity, a reservoir to contain the solution to be sprayed, and one or more atomizers. The compressed air supplied to the atomizers shall be passed through a filter to remove all traces of oil or solid matter and shall be at an absolute pressur
37、e of 70 kPa3) to 170 kPa. NOTE 3Atomizing nozzles may have a “critical pressure” at which an abnormal increase in the corrosiveness of the salt spray occurs. If the “critical pressure” of a nozzle has not been established with certainty, control of fluctuations in the air pressure within 0,7 kN/m2 (
38、 0,1 psi), by installation of a suitable pressure regulator valve minimizes the possibility that the nozzle will be operated at its “critical pressure”. In order to prevent evaporation of water from the sprayed droplets, the air shall be humidified before entering the atomizer, by passage through a
39、saturation tower containing hot water at a temperature several degrees Celsius higher than that of the cabinet. The appropriate temperature depends on the pressure used and on the type of atomizer nozzle and shall be adjusted so that the rate of collection of spray in the cabinet and the concentrati
40、on of the collected spray are kept within the specified limits (see 8.2). The level of the water must be maintained automatically to ensure adequate humidification. The atomizers shall be made of inert material, for example glass or plastics materials. Baffles may be used to prevent direct impact of
41、 spray on the test specimens and the use of adjustable baffles is helpful in obtaining uniform distribution of the spray within the cabinet. The level of the salt solution in the salt reservoir shall be maintained automatically to ensure uniform spray delivery throughout the test. 3) 1 kPa 1 kN/m2 0
42、,01 atm ISO 9227:1990(E) BSI 01-19993 4.4 Collecting devices At least two suitable collecting devices shall be available, consisting of funnels made of glass or other chemically inert material, with the stems inserted into graduated cylinders or other similar containers. Funnels with a diameter of 1
43、00 mm have a collecting area of approximately 80 cm2. The collecting devices shall be placed in the zone of the cabinet where the test specimens are placed, one close to an inlet of spray and one remote from an inlet. They shall be placed so that only spray, and not liquid falling from specimens or
44、from parts of the cabinet, is collected. 4.5 Re-use If the equipment has been used for a spray test or for any other purpose with a solution differing from that specified for the test to be carried out, it shall be thoroughly cleaned before use. The equipment shall then be operated for a minimum per
45、iod of 24 h and the pH of the collected solution measured to ensure that pH is correct throughout the entire spraying period, before any specimens are placed in the chamber. 5 Method of evaluation of the corrosivity of the chamber To check the reproducibility of the test results for one piece appara
46、tus or for similar items of apparatus in different laboratories, it is necessary to verify the apparatus at regular intervals as described in 5.1.1 to 5.1.3. 5.1 NSS test 5.1.1 Reference specimens To verify the apparatus, use four reference specimens 1 mm 0,2 mm thick and 50 mm 80 mm, of CR4 grade s
47、teel according to ISO 3574, with a practically faultless surface4), and a mat finish (arithmetical mean deviation of the profile Ra = 1,3 m 0,4 m). Cut these reference specimens from cold-rolled plates or strips. Clean the reference specimens carefully immediately before testing. Besides the specifi
48、cations given in 6.2 and 6.3, cleaning shall eliminate all traces of dirt, oil or other foreign matter capable of influencing the test results. Use one of the following methods: a) Clean the reference specimens by vapour degreasing with a chlorinated hydrocarbon. Use three successive treatments of 1
49、 min each, with an interval of at least 1 min between successive treatments. b) Thoroughly clean the reference specimens with an appropriate organic solvent (hydrocarbon, with a boiling point between 60 C and 120 C) using a clean soft brush or an ultrasonic cleaning device. Carry out the cleaning in a vessel full of solvent. After cleaning, rinse the reference specimens with fresh solvent, then dry them. c) Other cleaning methods may be used, after agreement between the interested parties, subject to the r
链接地址:https://www.31doc.com/p-3735929.html