Corrosion testing accelerated weathering steels

Horton et al. [55] observed that when steels containing Cu and Ni are exposed in industrial and marine atmospheres, the Cu and Ni appear in the mst layers both in the loose outer and adherent inner mst on skyward and ground ward surfaces. Also it was shown by chemical analysis that Ni, Cu, Cr and Mn from weathering steel appear in the mst layer and provides protection. Presence of chlorides in the atmosphere accelerates corrosion of steels leading to the formation of basic Fe ", Fe chlorides and jS FeOOH. Townsend et al. [56] conducted 8-year atmospheric corrosion tests on weathering steel in mral, industrial and marine environments with different heated conditions and indicated that heat treatments have no effect on the corrosion resistance/performance of weathering steels. 

Corrosion rate of weathering steels was found lower with respect to mild steels in accelerated laboratory tests. They corrode most rapidly with respect to field exposure test... 

Present research work has been carried out in two parts field exposme tests and accelerated laboratory tests on unexposed panels. Under field exposme test three representative sites PI very close to sea shore and free firom SO2, P2 away from sea with presence of SO2 and P3 industrial environment with presence SO2 were chosen. Analytical techniques (EDX, XRD and Raman spectroscopy) were used for rust characterisation and SEM was employed for understanding the morphological state. Corrosion rates were estimated after different periods of exposure at sites. It is found that though accelerated laboratory test can predict the general trend of corrosion, actual field test data cannot be created in laboratory. So an attempt was made to simulate protective rust coating in the laboratory that is typical of field exposure protective rust formation on weathering steel. 

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