Corrosion of Carbon Steel by One Month Atmospheric Exposure in Niigata

Corrosion of Steel by Atmospheric Pollution (Part 1)

Abstract

For investigation of effects of environmental factors on atmospheric corrosion of carbon steels in Niigata city, firstly, preliminary tests were carried out at 75 setting points in the city during the 10 months from January 1973. Then, one month exposure test was carried out at 35 setting points in the period of 4 years from July 1974. In the same period, concentrations of atmospheric pullutants and meteorogical elements were measured. The summary of results are as follows: 1) Corrosion rate was high in autumn and winter seasons. This fact showed that chloride was carried from the sea by northwestern monsoon, and that was good agreement with the measured results of chloride concentration, the wind direction and the wind velocity. 2) All of the setting points exist in the short distance within 6km from the seashore. In winter season, Niigata city was covered by such a high concentration of chloride (100-600μg/day/100cm²). On the contrary, chloride concentrations and corrosion rates were decreased significantly in spring and summer seasons. 3) According to the results of analysis in single correlation coefficients, relationship between any two factors among the three ones of chloride concentration, the wind velocity and corrosion rate showed 1% level of significances. Chloride had the largest effect on the atmospheric corrosion among those three environmental factors. This fact agreed with the results mentioned above 1). 4) The pollution from the industrial or urban area was not neglected in the corrosion rate increasing.