Posted by Trevor Roy.
The cause of the mysterious corrosion in the Duluth-Superior harbor has baffled scientists for more than ten years until now.
Dr. Brenda Little a senior scientist with the Navy Research Lab in Mississippi said "The problem is a galvanic corrosion that's caused by copper depositing on carbon steel so that 2 dissimilar metals are in contact.
It's actually a little bit more complicated than that.
Naturally forming Iron Oxidizing bacteria in the lake join together and form tubercles on the steel pilings.
That prevents oxygen from getting in the area between the organic tubercles and the metal.
It is in that area where the copper leeches in and causes the corrosion.
To further complicate matters, the ice on the harbor rubs off the tubercles starting the process over again.
Now that one of the causes is determined Port officials can get to work on finding the best way to prevent corrosion.
Jim Sharrow with the Duluth Port Authority said "You can do that with coatings and with protective layers, unfortunately we have the abrasion from the ice and we have to identify coatings that can live through this difficult winter, ice conditions and scour we have."
Scientists will be studying the corrosion for a little while longer trying to answer some lingering questions like why the tubercles don't form in deeper waters and if similar corrosion occurs any where else in the world.
The tubercles have been eating away at the pilings for more than thirty years.
It's estimated that 50,000 pounds of steel are lost every year due to the corrosion.
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