ISO 11474 pdf download.Corrosion of metals and alloys — Corrosion tests in artificial atmosphere — Accelerated outdoor test by intermittent spraying of a salt solution (Scab test)
1 Scope
The purpose of this International Standard is to define a method of assessing the corrosion resistance of metals by an accelerated outdoor corrosion test. In this International Standard, the term “metal” includes metallic materials with or without corrosion protection. The accelerated outdoor corrosion test applies to — organic coatings on metals; — metallic coatings (anodic and cathodic); — chemical conversion coatings; — metals and their alloys. The method is especially suitable for comparative testing in the optimization of surface treatment systems.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At 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 ISO maintain registers of currently valid International Standards. ISO 281 0:— 1 ) , Paints and varnishes — Notes for guidance on the conduct of natural weathering tests. ISO 8407:1 991 , Corrosion of metals and alloys — Removal of corrosion products from corrosion test specimens . ISO 8565:1 992, Metals and alloys — Atmospheric corrosion testing — General requirements for field tests . ISO 9226:1 992, Corrosion of metals and alloys — Corrosivity of atmospheres — Determination of corrosion rate of standard specimens for the evaluation of corrosivity.
3 Reagents
Salt solution, prepared by dissolving a sufficient mass of sodium chloride in distilled or deionized water to a concentration of 30 g/l ± 1 g/l. The distilled or deionized water used shall have a conductivity not higher than 2 mS/m at 25 °C ± 2 °C. The maximum permissible amounts of impurities in the sodium chloride are given in table 1 . Prior to use, check the pH of the salt solution by 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 0,3 pH units or less. If the pH value determined is outside the range 6,0 to 7,0 adjustments are to be made by adding to the alt solution diluted hydrochloric acid or sodium hydroxide of analytical grade.
4 Apparatus
4.1 Spray bottle, capable of producing a finely distributed mist. 4.2 Exposure frames, for holding the test specimens in an appropriate position. The frames shall be designed in accordance with the requirements of ISO 8565. They shall normally hold the test specimens at an angle 45° to the horizontal plane and face the equator. Other exposure angles and orientations may also be agreed upon. The frames shall be located so that the test specimens are neither protected nor shaded by nearby objects. The frames shall be positioned so that the reverse sides of the test specimens are freely exposed to air and so that no water runs off from one test specimen to another. During exposure, the test specimens shall not be in direct contact with metallic parts and, if possible, not in contact with wood or other porous materials. If the test specimens are set in tracks, suitable drainage holes shall be made to prevent water collection. The frames shall be positioned so that all test specimens are at least 0,75 m above ground level.
5 Test specimens
Test specimens (of the material to be tested for corrosion resistance) shall be prepared according to the general requirements given in ISO 8565. The simplest and most common type of test specimen is a flat panel, but valuable information can also be obtained by carrying out tests on structures. Structures which encase water may show early damage. For each series of test specimens, data records shall be kept including the following information. a) Specification of material to be tested. For surface treated materials: type of base material, its pretreatment, type of coating, method of application and dry coat thickness.