Influence of Dissolved Inorganic Nitrogen on Accelerated Low Water Corrosion of Marine Steel Piling

Accelerated low water corrosion (ALWC) is the term given to unusually high levels of corrosion immediately below the low water level in seawater exposures of steel piling. It has been associated with microbiologically influenced corrosion but conclusive evidence is lacking. Using published data for the corrosion of steel piles exposed for periods up to 27 years at various U.S. harbor and other locations, it is shown that the severity of ALWC is correlated with the concentration of dissolved inorganic nitrogen, a critical nutrient for microbiological (bacterial) activity in seawater. This was shown previously for short-term exposures and establishes that ALWC is indeed microbiologically influenced. It also provides a means of assessing the likelihood of long-term risk of occurrence of ALWC.