BS ISO 22479:2019 Corrosion of metals and alloys – Sulfur dioxide test in a humid atmosphere (fixed gas method)
BS ISO 22479:2019 pdf download.Corrosion of metals and alloys – Sulfur dioxide test in a humid atmosphere (fixed gas method).
5.3 Source of sulfur dioxide.
The source of sulfur dioxide should be a gas cylinder with a volume concentration of more than 99,9 %. It shall be fitted with appropriate regulating and measuring apparatus to ensure the supply of the correct volume of gas. The volume of gas delivered into the test cabinet should be measured by a calibrated flow meter. Another measuring instrument works with squeezing out a viscous liquid paraffin for the volume of the gas for 0.2. 1.0 and 2,0 I.
WARNING — Sulfur dioxide (CAS no. 7446-09-5) is toxic, corrosive and irritating. Handling of sulfur dioxide shall be restricted to skilled personnel or conducted under their control. The apparatus shall be used and maintained by skilled personnel, not only so that the procedures can be performed correctly, but also because of the hazards to health and safety that are involved.
5.4 Conditioning of a new cabinet.
In order to minimize the ettect from the material ot the cabinet by sultur dioxide, a new cabinet shall be operated at least one test cycle in accordance with the procedures given in 82 to 85 without test specimens. The conditioning shall conform to TableJ. with 2,0 I of sulfur dioxide.
6 Test specimens
The number, type, surface roughness, thickness of coatings, shape and dimensions of test specimens shall he selected according to the specification for the materials or product being tested. When not specified, details concerning the test specimens shall be agreed between the interested parties.
A typical specimen size is 150 mm 100 mm by 0,75 mm to 1,25 mm thickness.
6.3.1 Metals and alloys
Thoroughly clean the test specimens before testing. The cleaning method depends on the nature of the surface and the contaminants. Abrasives shall not include the use of any abrasives or solvents that may attack the surface of the test specimens. Take care that the test specimens are not recontaminated after cleaning, by excessive or careless handling.
If test specimens are cut from a large coated article, the cutting shall be carried out in such a way that the coating is not damaged, especially in the area adjacent to the cut. Unless otherwise specified, the cut edges should be adequately protected by coating with a suitable medium that is stable under the conditions of test, such as wax or adhesive tape.
6.3.2 Paints and varnishes
Unless otherwise specified or agreed, the test specimens shall be prepared in accordance with ISO 1514 and then coated by the specified method with the product or system under test. The back and edges of the test specimens should be coated with the product or system under test.
Dry (or cure) and age (ii applicable) each coated test specimen for the specified time and under the specified conditions and, unless otherwise specified, condition them at a temperature of (23 ± 2) °C and a relative humidity of (50 ± 5) % for at least 16 h, with free circulation of air and not exposed to direct sunlight. The test procedure shall then be carried out as soon as possible.
Determine the thickness, in micrometres, of the dried coating by one of the non-destructive procedures described in ISO 2808.
6.4 Arrangement of the test specimens
The distance between test specimens shall be not less than 20 mm. The distance between the edge of the test specimens and a wall of the test cabinet shall be not less than 100 mm. The test specimens shall be arranged in such a way that they cannot protect each other from the influence of the environment. The distance between the lowest edge of the test specimens and the surface of the water shall be greater than 200 mm The contact area between test specimens and their supports shall be as small as possible
The orientation of the exposed test surface in the test cabinet is critical. Unless otherwise specified, test specimen shall be mounted at an angle between vertical and (15 ± 2)° to the vertical, with the area of primary interest facing up.
NOTE This is common practice for testing metallic specimens and measures to protect them from corrosion. When testing assemblies or enclosures, it Is preferable to mount the specimen at the same angle as in typical use.
The total exposed surface area of the test specimens for one test shall be (0,5 ± 0,1) m2 for each (300 ± 10)1 of the test cabinet. For different volumes of the test cabinet, the total exposed surface area is to be adjusted proportionally. When the total exposed surface area is less than 0,5 m2 for 300 I of the cabinet, substitute specimens shall be added to obtain a total surface area of 0,5 m2. The materials of the substitute specimens shall be the same as of the test specimens. Otherwise, test results may be different, since the influence (absorbance) of sulfur dioxide differs by materials.
7 Test conditions
7.1 Test cycles
One test cycle is 24 h, either Method A or Method B.
In Method A, test specimens are exposed to sulfur dioxide for 24 h. If test specimens are affected seriously by the temperature and humidity, Method B should be chosen.
In Method B, test specimens are exposed to sulfur dioxide for 8 h, followed by exposure to a standard atmosphere for 16 h.
The test conditions of Method A and Method B are shown in Table I and TablL respectively.
For metallic and non-organic coatings, 0,2 I volume of sulfur dioxide should be used. For paint and varnish, 0,2 1 or 1,0 1 volume of sulfur dioxide should be used. Generally, 0,2 I volume of sulfur dioxide is recommended where the coating thickness does not exceed approximately 40 m. 2,0 I volume of sulfur dioxide is used by agreement between the interested parties or according to product specifications, such as corrosion resistant coatings (e.g. hard chrome plating, anodised coating).
7.2 Test duration
The test duration shall be as designated by the specification for the material or product being tested. When not specified, the test duration shall be agreed between the interested parties.
The test may be finished if a specified degree of corrosion has been reached, or if the appearance or function of test specimens has otherwise been impaired to an unacceptable level.
Recommended numbers of test cycles are: 1, 2, 5, 10, 15 or 20.
8.1 Introduction of water
Introduce (2,0 ± 0,2) I of distilled or deionized water with a conductivity not higher than 5 iS/cm at (25 ± 2) °C inside the test cabinet.
NOTE This quantity is for 300 I capacity of the test cabinet. It depends on the capacity of the test cabinet proportionally (see 52).
8.2 Arrangement of the test specimens
Place the test specimens in position (see GA), and close tightly the test cabinet.
8.3 Introduction of sulfur dioxide
Introduce 0,21, 1.01 or 2.01 of sulfur dioxide at (23 ± 5) °C into the test cabinet through the gas inlet port.
NOTE This volume is for 300 I capacity of the test cabinet. It depends on the capacity of the test cabinet proportionally (see 52).
The test cycle begins when sulfur dioxide is introduced.
8.4 Heating the test cabinet
The temperature of the test cabinet shall he raised to (40 ± 3) °C in less than 1,5 h and maintained for the specified period.
8.5 Introduction of standard atmosphere
In the case of Method B, the standard atmosphere is introduced by turning off the heater while opening and/or ventilating the test cabinet,
The temperature of the test cabinet shall be lowered to (23 ± 5) °C, less than 75 % relative humidity in approximately 1 h and be maintained for the specified period.
Alternatively, the test specimens may be transferred to a different environmental cabinet capable of being maintained at the conditions of standard atmosphere.
8.6 Replacement of water and sulfur dioxide
The water and the sulfur dioxide in the test cabinet shall be replaced for each test cycle (24 h).BS ISO 22479 pdf free download.BS ISO 22479:2019 Corrosion of metals and alloys – Sulfur dioxide test in a humid atmosphere (fixed gas method)