Localized corrosion of steel sheet piling

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Localized corrosion of steel sheet piling

Melchers, Robert E. / Jeffrey, Robert J. / Usher, Kayley M.

When steel sheet piling suffers accelerated low water corrosion the webs and flange-web regions of individual piles often perforate first, for reasons not fully understood. To investigate this, samples of the cross-sections of typical U and Z profile sheet piling were exposed to natural seawater for 1, 2 and 3 years. They showed localized corrosion in the central region and also near the flange-web junctions. These locations were found to have more material defects and segregation and show composition differences. Perforation by long-term corrosion of sheet pile profiles will occur earlier in the webs when the webs are thinner than the flanges, as is the case for some commercial pile profiles. For sheet piling with similar wall thickness profiles throughout, the earlier perforation of the in- and out-pans of U shaped steel sheet piling, the webs of Z- and I-shaped steel piling, and the earlier perforation of the corner regions, is correlated with localized segregation and of differences in metal composition. It is well-known in the industry that these differences across the profile arise from the pile manufacturing process and are similar along the length of each steel pile. The perception that modern steel piling is less prone to localized corrosion perforation is consistent with well-documented steel industry information that modern steel making produces steels having smaller differences in metal composition and less segregation than was typical for older steels.It is proposed these observations are linked to localized sheet pile perforation after long exposure to seawater.