Atmospheric corrosion resistance of structural steels

The main objective of this paper is to provide engineers with data on thickness loss of structural steel members resulting from corrosion. To this end, the writers have collected atmospheric exposure data from many research reports and journal papers. The data are presented in graphs of thickness loss versus exposure that demonstrate the effects of types of environment and steel. The environments include rural, industrial, and marine, becoming increasingly severe in that order. The steels under consideration are A242, A588, copper, and carbon steels, with their corrosion resistance decreasing in that order. Comparisons of the data with the medium corrosivity bands for weathering and carbon steels help to determine the severity of environments and the corrosion resistance of steel compositions. For bare exposed structures, a corrosion allowance should be added to all member thicknesses arrived at by stress calculations can be estimated by extrapolating an applicable thickness loss curve to the end of the service life of the structure. The corrosion allowance thickness loss data obtained from simple test specimens, mostly of the 150 X 100 mm size of an index card, must be applied carefully to complex structures such as a bridge, which has a variety of details with different exposure conditions. When portions of a bare, exposed structure remain damp or wet for long periods of time, thickness losses can be much higher than those reported for test specimens exposed at 30degrees facing south. Good structural detailing that prevents moisture accumulation is of utmost importance.