Abstract
Atmospheric corrosion testing of 117 low alloy steels was conducted for 8 and 12 years in industrial and rural sites in Japan. In the industrial site carbon steels corrode 4 times more than those in the rural site. These results show the following tendency about the effect of the alloying elements.
Industrial site: P>Cu>Mo>Cr>Si
Rural site: P>Cu>Si>Cr>Ni
From these data the effect of alloying elements is quantified by multiple regression analysis. Also, the formula between weight loss and exposure year is obtained as Y=A⋅exp(B/X)⋅YC and the corrosion loss for 20 years exposure is estimated. The surface rust of the weathering steels is thin uniform layer and has less crack or pore, but alloy rich, special structured layer is not detected in the rust by X-ray diffraction, chemical and EPMA analyses and polarized-light microscopy.
