Corrosion of Ports
An aggressive form of corrosion has eaten away at steel pilings along commercial ports on Lake Superior, and some pilings are so worn they're on the verge of failure. Researchers are trying to pinpoint the cause of the freshwater corrosion.
Perforations affect most sheet piling with an original thickness of three-eighths of an inch or less that has been in the harbor for more than 30 years. Most 3/8-inch docks probably will face collapse in the next five to 10 years unless their steel pilings are replaced.
The steel piles became more visible as Lake Superior fell 18 inches from its average historical level. Dramatic corrosion can be seen on Coast Guard range towers near the Bong Bridge and at the foot of the Duluth Missabe & Iron Range Railway ore docks in Minnesota.
Scientists are focusing on microbes and how they affect harbor corrosion. A study of organisms found on the port's steel pilings has isolated two types of bacteria. One appears to be an iron oxidizer and the other an iron reducer.