Part 1: Architect’s Guide 1 - 54 Atmosphere and climate are parameters that have a significant influence on the aggressiveness of corrosion. Atmosphere The general atmospheric conditions at the building location affect the rate of corrosion: there are four general conditions: Rural: alternation of wet and dry atmosphere – absence of pollutants Urban: alternation of wet and dry conditions – present of sulphur dioxide (SO2) Marine: high relative humidity – presence of chlorides which accelerate corrosion. Industrial: presence of chemical agents – aggressive corrosion linked to degree and rate of pollutants Climate Heat and humidity are factors which accelerate the phenomenon of corrosion. In tropical climates, aggressive corrosion in rural environments is comparable with that in large industrial areas in temperate climates. Some elementary precautions In steel construction design, every means of limiting the effects of corrosion should be adopted: Avoid creating areas of moisture and water retention for elements which are exposed to weather Avoid contact between materials which have different electro-chemical potentials (e.g. aluminium and unprotected steel). Protection of steel construction elements It is advisable to adapt the degree of protection to the conditions in which the steel construction elements are installed. There are two main forms of protection: Painting Galvanizing. 6.5.2 Paint protection Table 6.6 summarizes common coating systems for corrosion protection. It is worth noting that steel structures located inside a building where the atmospheric conditions are neither wet nor aggressive, and are permanently protected from the weather, would not suffer corrosion to the extent that it affects their resistance, even if they were not protected. However, what cannot be excluded is the unattractive appearance of rust: this can be prevented by applying a light paint coating. Surfaces which remain unprotected must be visible in order to detect any unexpected degree of corrosion.
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