New clues to Duluth-Superior’s mysterious harbor rust

Posted on May 17, 2008 under Environment, Government Issues, Industry News, Ports |

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by Bob Kelleher | Source: Minnesota Public Radio

Jim Sharrow has a few rusty props too, in his office at the Duluth Seaway Port Authority. One of the mysteries about the rust is where it shows up, and where it doesn’t.

Sharrow said in Lake Superior, just outside the harbor, there is little to no rust, but it turns up inside the harbor.

“There’s certain parts of the harbor where it’s occurring at almost twice the rate as it is in other parts of the harbor,” Sharrow said.

There’s a long list of suspects — from tannin-rich water, to stray electrical current, to chemicals like road salt. And, Sharrow said, it looks like the corrosion wasn’t an issue until about 30 years ago.

“All along to us, it has appeared that something changed in our harbor in the 1970s to greatly increase the rate of corrosion,” said Sharrow.

Recently they’ve observed similar rust in other places around Lake Superior far from Duluth.

Read the full story, photos at Minnesota Public Radio >>