The study on the effects of air pollution on the material damages in northeast Asia

The material exposure tests have been carried out since 1993 to evaluate the relationship between air pollution and material corrosion with the cooperation of the researchers in Japan, China and Korea. The test pieces such as bronze, copper, marble and carbon steel have been exposed under both unsheltered and rain-sheltered outdoor condition separately at 18 sampling sites in East Asia. At the same time, the concentration of SO₂ and NO₂has been measured simultaneously with passive sampler. The meteorological data were collected from the AWS(Automated weather station) in each country and chemical compositions of wet deposition were also analyzed by the bulk sampling of rainfall every month. As the results, it was found that the corrosion rates of test pieces in the ambient air were appeared to be in the order of carbon steel> marble> bronze≥copper. The corrosion rates of test pieces in the unsheltered outdoor condition were 2.34 to 5.88 times larger than those in rain-sheltered condition. It was also found that the corrosion rate in the heavy polluted area in China was the highest, and the corrosion rates of the metal pieces were generally proportional to SO₂concentration. Between two sites in Korea, the test peices at Daegu site showed higher corrosion rates that would be due to the higher SO₂concentration.