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

Abstract

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.

Investigations for structural safety assessment of corroded cast iron bridge piers

“…This vertical effect is summarised in the schematic corrosion profile shown in Figure 3. Typically, compared with the corrosion in the immersion zone, there is less corrosion in the tidal zone and more in the splash zone (Melchers and Jeffrey 2012). Only quite recently has similar behaviour been reported for cast iron bridge piers (Melchers, Herron, and Shimodaira 2013).…”

“…Subsequent to the investigation reported here, new research for the corrosion of sheet and other steel piling in marine environments has shown a high degree of correlation between corrosion severity and concentration of dissolved inorganic nitrogen (DIN) (Melchers and Jeffrey 2012;Melchers 2014). This was despite the fact that the standard test kits for bacteria had proved negative.…”

“…Figure 3 also shows a zone of very high corrosion marked 'accelerated low water corrosion' (ALWC). This sometimes occurs for steel piling in harbours and has been correlated with MIC caused by elevated levels of nutrients in the water (Melchers and Jeffrey 2012;Melchers 2014). No reports of ALWC are known for cast iron piers or other cast iron structures but, on the basis of the evidence for structural steels, it was considered prudent to consider this possibility and to perform appropriate tests.…”

Localized corrosion of carbon steel in marine media: Galvanic coupling and heterogeneity of the corrosion product layer

“…For vertical steel structures, differential aeration can also lead to the localization of the corrosion process. The immersed part of the structure that is close to the seawater/air interface is more aerated and may thus be a cathodic zone with respect to lower parts of the structure [9][10][11]. In both cases, the heterogeneity of the medium is the origin of the local nature of the corrosion phenomenon.…”

Research on water-line corrosion of carbon steel by wire beam electrode technique

“…He thought the area near airliquid interface was full of dissolved oxygen but the area under waterline was comparatively short of dissolved oxygen. Jeffrey [3,4] studied the corrosion of long vertical steel strips in the marine tidal zone. It showed that the steel right near waterline had slightly corroded, the heaviest corrosion happened about at 250mm above the waterline and 200mm below the waterline.…”