A great problem for the Great Lakes
Steel sheet piling and structures are corroding in Lake Superior. This finding comes after researchers and experts began investigating the issue in 2004.
Gene Clark of the University of Wisconsin Sea Grant Institute and Chad Scott of AMI Consulting Engineers P.A. have been working alongside one another to find a solution to the issue of corrosion in the Great Lakes, specifically off of the Duluth-Superior Harbor.
“Corrosion is not typically seen in fresh water,” Clark said. “99 percent of people had never heard of this.”
Clark and Scott’s findings were detailed in an edition of “The River Talks” in Superior, Wisc. on Feb. 8 at Barker’s Waterfront Grille.
According to the University of Wisconsin Seat Grant Institute, it could cost over $120 million to repair the steel that was weakened by corrosion.
“An initial inspection in 1989 found that steel corroded all of the way through these steel beams in the water,” Scott said.
Clark went on to say that this was unheard of. The corrosion was said to have been dramatically increased around this time, after the passing of the Clean Water Act of 1972. This leads to questions in and of itself.
Microorganisms play a great factor in the issue of corrosion due the water chemistry.
With the help of Dr. Randall E. Hicks, a University of Minnesota Duluth biology professor, samples were taken of the corrosion.
“What was found was iron-oxidizing material in the growths,” Clark said.
This is because that is precisely what causes steel to breakdown.
“The corrosion of structural steel is an electrochemical process that requires the simultaneous presence of moisture and oxygen. Essentially, the iron in the steel is oxidised to produce rust, which occupies approximately six times the volume of the original material. The rate at which the corrosion process progresses depends on a number of factors, but principally the ‘micro-climate’ immediately surrounding the structure,” a website on corrosion said.
But why is there such an issue in the Great Lakes and why have the “fixes” flopped?
“The problem that we have is most of the solutions are for places that don’t have eight to ten feet of ice in the winter,” Scott said. “Big vessels come into the harbor and ram ice into the steel.”
While the corrosion issue has been identified, it has not been solved. The minor fixes of applying a coat are helpful, but very expensive. There have been six to eight coats found, according to Clark, but none of them are entirely ideal.
Moving forward, Clark and Scott will continue their efforts in finding a solution to this problem. They hope to share their findings in an effort to get more word out about the issue of corrosion in the Great Lakes.