In 1987 a co-operative field exposure program within the UN Economic Commission for Europe was initiated. The aim of the program is to evaluate the effect of sulfur pollutants in combination with NOx and other pollutants on the atmospheric corrosion of important materials. This work presents results from the evaluation of the electric contact materials nickel, copper, silver and tin after 4 years of exposure.
Dry deposition of SO2 dominates the corrosion of nickel, which forms amorphous and crystalline basic nickel sulfate, whereas both O3 and NO2 accelerate the dry deposition of SO2 on copper. Silver forms Ag2S as the dominating corrosion product. Since H2S is not measured within the program it has not been possible to estimate its contribution. The formation of oxides with different stoichiometries dominates the corrosion of tin and no equation has been found that relates the weight increase of tin to environmental data. Particulate ammonium sulfate contributes to the weight increase of all metals.