Regional Air Pollution Study: Effects of Airborne Sulfur Pollutants on Materials

摘要

Samples of galvanized steel, weathering steel, A1 2014 and 7079 stress samples, silver, marble, nylon and two types of house paint were exposed at nine sites of the Regional Air Monitoring System in the St. Louis area. Wind speed and direction, temperature, dew point, total sulfur, SO2, H2S, O3, NOx, total hydrocarbons, total suspended particulate matter, sulfate and nitrate were recorded. For galvanized steel a pronounced effect of time of first exposure was observed. The corrosion behavior of weathering steel was not seasonally dependent. House paint showed discontinuous erosive behavior. Exposure to the south was more erosive than exposure to the north. Rates for latex paint were higher than for oil based paint. The erosion rate of marble decreased with time. At some sites 50% reflectance loss of silver occurred after 3 months exposure. All samples of A1 7079 at 25 Ksi failed in less than 255 days, while complete failure at 15 Ksi occurred between 277 and 630 days. For A1 2014 more scatter was observed. The pollution levels in St. Louis were found to be rather low. Ozone showed similar seasonal changes as the temperature. Sites close to the center of St. Louis had lower ozone but higher NOx and total hydrocarbon levels. Sulfate was about twice as high in summer as in winter. A first attempt at multiple regression analysis was made. Apparent inconsistencies in the estimated effects are believed to be due to multicollinearity.