Atmospheric corrosion deicing salts

The source of chloride is seawater as well as the deicing salts used on roads. The hydrogen chloride is also present in seawater aerosols. The corrosion of copper and its alloys in marine atmospheres has been studied and a corrosion rate of 600-700 pg/cm2 yr averaged over a period of 8 yr has been reported.50... 

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. 

The severity of external automotive corrosion varies considerably throughout the world, due to differences in the chemistry of the environment [/-3]. The severest corrosion environments are in the snowbelt areas where deicing salts are used and along coastal areas where warm, humid, salt atmospheres exist. During the 20th century, the chemistry of the environment changed drastically. As a result of those changes, the corrosivity of the automobile environment increased. 

With this requirement profile, these steels can also be considered for applications in marine atmosphere or industrial atmospheres. The steels 1.4003 (X2CrNil2) and 1.4512 (X2CrTil2) are not likely to show any corrosion-related cross-sectional reductions, even over periods of several decades, with the exception of highly aggressive conditions. Crevice corrosion can be expected under heavy chloride exposure and in the presence of crevices. Such critical conditions do not result from seawater exposure only, but are also seen inland due to deicing salt, etc. The ferritic chromium steels are not, by the way, formulated with crevice corrosion resistance in mind [100]. 

Reinforced concrete electrochemical protection methods used against corrosion caused by contamination with chlorides or the carbonization process may be used for new structures, as well as those already used in soil, water, and atmospheric environments. The first practical CP application was realized in the U.S. A. for the protection of a bridge contaminated with deicing salts (Stratfull, 1974). 

Marine. Fine windswept chloride particles that get deposited on surfaces characterize this type of atmosphere. Marine atmospheres are usually highly corrosive, and the corrosivity tends to be significantly dependent on wind direction, wind speed, and distance from the coast. It should be noted that an equivalently corrosive environment is created by the use of deicing salts on the roads of many cold regions of the planet. 

The galvanic corrosion of aluminum is usually mild, except in highly conductive media such as seawater, wind-blown sea spray, and salted slush from road deicing salts, when corrosion can be appreciable. In natural surface waters and nonsaline atmospheres, the galvanic corrosion of aluminum is rarely significant, although rain mnoff from copper and its alloys pit aluminum qtpreciably. 

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