Protective paint coatings on steel: Accelerated corrosion test in high humidity air containing small amounts of sulphur dioxide (NT BUILD 377)

Abstract

SCOPE AND FIELD OF APPLICATION

This method specifies the test equipment, preparation of test specimens and the procedure for accelerated corrosion tests on protective paint coatings on steel. The corrosion test is conducted in an artificial atmosphere of air containing 1 ppm sulphur dioxide. Exposure takes place at a constant relative humidity of 95 % and at a constant temperature of 23 ºC. Assessment of the rust protective ability of a coating is based on the measurement of the spread of visible defects, such as blisters, corrosion, and loss of adhesion caused by intentional, mechanical damage in the protective paint coating prior to the test. The relative rust protective abilities of the paint coatings tested are estimated by comparing the test results with those from reference specimens of known durability properties. The reference specimens are exposed and evaluated with the test specimens during testing. The method has been shown to be valid in generating corrosion damage on painted steel as observed in marine environments during outdoor exposure. This method applies to water-borne and solvent-borne paint systems on degreased, blast-cleaned, or phosphated steel substrates. The method is not intended to simulate such factors of environmental influence as solar irradiation, drying, wetting which may cause cracking, flaking, or chalking of the paint film. These defects may influence the corrosion of the steel substrate during long-term use.