Atmospheric corrosion chlorine-containing compounds

One of the most important factors affecting atmospheric corrosion is the presence of specific pollutants. In areas having low atmospheric pollution, corrosion rates are correspondingly low. The presence of atmospheric pollutants such as the various oxides of nitrogen, sulfur-containing compounds, chlorine-containing compounds, and other less common pollutants will stimulate corrosion. 

Cause Stress corrosion cracking was established to be a major cause. Chlorine-containing compounds were transferred via the pool atmosphere to surface away from the pool itself resulting in the production of a highly corrosive film on the stainless steel rods which supported the roof structure. The failure occurred around 30°C in highly stressed components which were not frequently cleaned. Such components included brackets, rods, bars, wire ropes, fasteners, etc. 

Atmospheric corrosion of metals is affected by contaminants such as chlorides from deicing or from airborne salt in marine atmospheres. Other sources are HCl production from the burning of chlorine-containing coals and the emission of chlorine from industrial processes. Hydrochloric acid is formed by photodissociation of chlorine, resulting in the production of chlorine radicals that are hydrogenated with organic compounds. 

As can be seen in Table 2-1, several industrial atmospheres contain halogen gases. In particular, chlorine and chlorine compounds may cause severe corrosion problems because of the high vapor pressures of many metal chlorides. Thus the formation of a protective layer of a solid state compound is impeded. If chlorine is the only reacting species, the process of chlorination can be described by... 

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