Abstract
Atmospheric corrosion behaviors of carbon steel and corrosive environmental factors were investigated at three exposure test sites in Fukui prefecture, which is located on the coast of Sea of Japan and at just about the middle of the main island of Japan. Corrosion rate of carbon steel coupon exposed at a rural site for one year（Jan.2010 ～Dec.2010）was measured to be 0.022 mm/y. Mean value of monthly precipitation rate of airborne salt analyzed by dry gauze method was 8.2 mgNaCl/（m2d）, and the time of wetness（TOW）was 3900 h. The corrosivity of the atmosphere in Fukui was classified as medium in the categories of corrosivity of the atmosphere in Japan by these measurement values.
Monthly corrosion rate of carbon steel decreased in the spring and summer of February to July and increased in winter of November to January. It was confirmed that the corrosion rates of each month were correlated with the amount of deposited salt, Ws, and daily average electricity, Q, measured by ACM（Atmospheric Corrosion Monitor）type corrosion sensor.
