Corrosion of long vertical steel strips in the marine tidal zone and implications for ALWC

The cause of the high corrosion losses below the low tide level on older steel piling (usually called Accelerated Low Water Corrosion – ALWC) is incompletely understood but usually linked to microbiological influences. Vertical 3–6 m long steel strips were exposed through the tidal zone at 13 different marine sites. After only 1–3 years good correlation was found between ALWC and local seawater average concentration of dissolved inorganic nitrogen, a necessary nutrient for microbiological activity. These results allow prediction of the likelihood of long-term ALWC through measurement of either short-term corrosion loss profiles or average nutrient levels.

► Corrosion of steel below low tide is influenced by nutrient concentration.
► Good correlation exists between severity of corrosion and nutrient concentration.
► Corrosion profiles and nutrient concentration can predict the likelihood of ALWC.