Accelerated low water corrosion of steel piling in harbours

Accelerated low water corrosion of steel piling in sea water harbours in the UK, Europe and elsewhere has been shown recently to be the result primarily of water pollution. Elevated levels of dissolved inorganic nitrogen in sea and brackish waters are responsible for microbiologically influenced corrosion of steel piling below the low water tide level. This is demonstrated in field data from 13 Australian experimental sites, nine US naval sites and some severe sites in Australia, Norway, Japan and the UK. Localised perforation of sheet piling, often associated only with the webs of U and Z profile piles, is shown to be the result of centreline segregation, porosity and composition differences in steel profiles. These stem from the steelmaking process and are likely to be less severe for modern steels. The results explain most of the observations for actual steel piling in various harbours, both vertically and horizontally (i.e. for U and Z and other pile profile types).