Influence of SO2 and NOx on atmospheric corrosion of steel

Abstract

Significant damages have been caused by sulfur and nitrogen pollutants produced by man activity to buildings and constructions including those linked to the cultural heritage in industrialized countries during the last century. These damages caused a substantial cost. It is considered that at present the figure I about nine thousand million US dollars each year. It has been very well established, that sulfur compounds, particularly sulfur dioxide, accelerate the degradation processes of many materials. More recent studies have also shown that the importance of other pollutants, such as O3, nitrogen oxides and organic acids on the degradation of materials. Salinity and sulfur compounds were determined every month by using accumulative methods at two test stations. Gaseous pollutants were also determined at two test stations by the use of volumetric methods. The corrosion of carbon steel was evaluated by weight loss. Data for pollutants and steel weight loss were processed. The results show that among the aerochemical factors, the most influential ones on the explanation for the variations of the corrosive activity of the atmosphere in the tested stations were nitrogen monoxide and ammonia, and that the interaction between chloride ions and NO causes an increase in AISI 1020 steel corrosion. It explains its great incidence detected at the Casablanca station, while SO2 influence is not significant on the steel corrosion changes.