![]() ![]() food-processing plants, laundries, breweries, dairies Production rooms with high humidity and some air pollution, e.g. Urban and industrial atmospheres, moderate sulphur dioxide pollution coastal area with low salinity Unheated buildings where condensation can occur, e.g. offices, shops, schools, hotelsĪtmospheres with low level of pollution: mostly rural areas Heated buildings with clean atmospheres, e.g. Ītmospheric corrosivity categories and examples of typical environments (BS EN ISO 12944-2 ) Corrosivity categoryĮxamples of typical environments (informative only) More information can be found in BS EN ISO 12944-2 and BS EN ISO 9223. However, environments can be broadly classified, and corresponding measured steel corrosion rates provide a useful indication of likely corrosion rates. ![]() Because of variations in atmospheric environments, corrosion rate data cannot be generalised. The rate at which the corrosion process progresses depends on a number of factors relating to the ‘micro-climate’ immediately surrounding the structure, principally the time of wetness and the atmospheric pollution level. However, these tend not to be significant for structural steelwork. The general corrosion process is illustrated here.Īs well as general corrosion, there are various types of localised corrosion that can also occur bimetallic corrosion, pitting corrosion and crevice corrosion. Essentially, the iron in the steel is oxidised to produce rust, which occupies approximately 6 times the volume of the original material consumed in the process. In the absence of either, corrosion does not occur. The corrosion of structural steel is an electrochemical process that requires the simultaneous presence of moisture and oxygen. Schematic representation of the corrosion mechanism for steel
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