Steal Corrosion in Lake Superior
Coastal Engineer Gene Clark stands tall with his arms folded across his chest. He’s listening intently as Structural Engineer and Diver Chad Scott speaks to a crowd of about forty people at the Breezy Point Inn in Superior, Wis.
The crowd, along with Clark and Scott are attending a monthly River Talk on February 8. These talks are hosted by Wisconsin Sea Grant and are a “free, informal speaker series about the St. Louis River Estuary in Duluth-Superior.”
Clark isn’t just listening to Scott speak. He’s also helping to speak to the crowd about steal corrosion — an issue that many believed could only occur in salt water.
“We couldn’t convince people it was an issue for fresh water,” says Scott.
Since about 1998, the two men have worked together to research the dangers and the real possibilities of steal corrosion in freshwater lakes such as Lake Superior.
As a diver, Scott has the ability to see parts of lakes, rivers, or oceans that most people will never see in a lifetime. As a diver, he also has the ability to assess and monitor the corrosion happening on steal structures, such as steal piling, two to three meters below the surface.
Although some of the corrosion is insignificant, other corrosion appears to be causing holes between 15 to 30 cm deep. As this corrosion progresses, the risk of structural failure increases.
The Duluth Seaway Port Authority estimates that in the Duluth-Superior Harbor there is 120 million dollars worth of possible repairs — or $1,500 per lineal foot.
Clark and Scott realized there was a problem and they knew they needed to work with other experts to determine what was causing the damage and how to fix it.
The coalition consisted of Scott’s diving team, experts in corrosion, microbiologist, chemists, University of Minnesota- Duluth’s Natural Resources Research Institute, Duluth Seaway Port Authority, Minnesota and Wisconsin Sea Grants, and U.S. Army Corps of Engineers.
Samples collected by divers from 44 different sites around the harbor were submitted to laboratory testing.
Dr. Brenda Little, a senior scientist for Marine Molecular Processes at the Naval Research Lab, found that there was copper platted bacteria inside the corroded pits.
Little found that a chemical reaction occurs between the naturally occurring iron oxidizing bacteria and the copper plated bacteria found inside the pits.
“Before people thought Chad just wanted dive jobs,” Clark joked.
Finally the two men had evidence to prove there was a problem in Lake Superior. Now it was time to find a solution.
Many of the solutions that already exist to help with steal corrosion are meant for climates where there isn’t ice. After testing a few different solutions, Scott found that hybrid epoxy coatings were most durable options to withstand Minnesota winters.
The epoxy is spread out on top of the corroded steal and on top of the epoxy a plastic form fitting shield is placed.
So far, the new solution has helped to protect 6,000 feet of steal piles. The epoxy has helped the problem —but it isn’t over yet.
“There’s still 14 miles in the Harbor that have corrosion,” says Clark.
Though their journey to research steal corrosion started in 1998, both men are happy with all the hard work and teamwork that has gone into the project.
“What we’re doing — came from every step of the process,” says Scott.
Clark and Scott plan on continuing to research and assist with fighting steal corrosion in Lake Superior along with other fresh water lakes that are experiencing similar problems.
Chad Scott-AMI Consulting Engineers P.A.
Gene Clark- Wisconsin Sea Grant