GLIN==> Duluth-Superior Harbor Corrosion Study Published; Lead Researcher to speak in Twin Ports Dec. 2

MEDIA ALERT:  Duluth-Superior Harbor Corrosion Mechanism Identified 

News release, JOURNAL article/cover attached, plus background story on
harbor corrosion from Duluth Seaway Port Authority's summer 2009
magazine.

 

 

November 23, 2009         For Immediate Release


Contact:  Jim Sharrow, (218) 727-8525                                   

 Chad Scott (218) 727-1206, x12            

To reach scientist Brenda Little, contact Shannon Breland, Public
Affairs, NRL, Stennis Space Center, (228) 688-5328 or 

shannon.breland at nrlssc.navy.mil <mailto:shannon.breland at nrlssc.navy.mil>


 

NOTE:  Brenda Little will be in the Twin Ports on Wed., Dec. 2 to
address the Harbor Technical Advisory Committee (HTAC) at a 9 a.m.
meeting in the Superior Public Library meeting room; she's scheduled at
approx. 9:35. 

 

Duluth, Minn. USA - Long-awaited research findings just published
identify one possible mechanism responsible for accelerated steel
corrosion in the Duluth-Superior harbor. The peer-reviewed paper
published in CORROSION, The Journal of Science and Engineering, outlines
a study led by Brenda Little, Senior Scientist, Marine Molecular
Processes, Naval Research Laboratory, Stennis Space Center. The study
was supported by the U.S. Army Corps of Engineers, Detroit District, and
the Duluth Seaway Port Authority.  

 

Entitled "Factors Contributing to Corrosion of Steel Pilings in
Duluth-Superior Harbor" (by R. Ray, J. Lee and B. Little), this research
demonstrates a specific sequence of biological, chemical and physical
events responsible for localized corrosion of carbon steel piling -
including the role ice scour plays in accelerating that process. 

 

Corrosion has been eating away at steel pilings in this harbor for over
30 years, consuming an estimated 50,000 plus pounds of steel a year.
Once identified in the late 1990s, scientists, engineers and local dock
owners (led by the Port Authority) immediately began researching
potential causes and ways to either stop it or protect remaining steel
structures.  

 

Little's findings confirm that ongoing repair and mitigation studies in
the local harbor are on the right track. The study also may give
engineers a basis for developing resistant steel alloys for new
construction and coatings that lengthen the lifespan of steel structures
already in place. Research will eventually lead to methods of
determining the likelihood of similar corrosion developing in other
freshwater harbors around the globe. 

 

"Now that we understand an exact mechanism, we can narrow down our focus
of how to best mitigate the problem in research and pilot projects"
noted Jim Sharrow, Port Authority Facilities Manager.  "Results will
help steer subsequent studies by Brenda (Little) and by UMD researcher
Randall Hicks. We are especially pleased to know that the Corps has
received an additional $300,000 targeted for corrosion research in
FY2010."                              

 

In layman's terms, conclusions of this study describe the process by
which specific iron-oxidizing bacteria attach to carbon steel, creating
a "nodule" of biomass and corrosion products.  Conditions beneath those
nodules (i.e. "tubercles") cause copper dissolved in harbor water to
precipitate and adhere to the iron.  When ice chunks scrape against
those pilings each winter, the tubercles break, exposing the
copper-covered iron to oxygen which, in turn, causes the steel in those
pitted areas to corrode at a faster rate...creating an almost "Swiss
cheese" effect in nearly 14 miles of steel pilings and dock walls along
the Duluth-Superior waterfront.  

 

Scientists describe this process more definitively in the study's
abstract: 

Field observations and laboratory testing were used to conclude that
aggressive localized corrosion of carbon steel pilings in
Duluth-Superior Harbor, Minnesota and Wisconsin, is caused by the
following sequence of biological, chemical and physical events.
Iron-oxidizing bacteria colonize the carbon steel sheet pilings and
produce tubercles, made up of intact and/or partly degraded remains of
bacterial cells mixed with amorphous hydrous ferric oxides. The reducing
conditions beneath the tubercles cause copper dissolved in the water to
precipitate. A galvanic couple is established between the copper layer
and the iron substratum. Ice scouring breaks the tubercles. Exposure of
the copper-covered iron to oxygen causes the galvanic current to
increase. The result is aggressive localized corrosion.  

 

Locally, a team of experts has been working collaboratively since 2004
to define the methodology for studying - and mitigating - the
accelerated corrosion problem in the Duluth-Superior harbor.  Several
pilot projects are well underway, looking into applications and
procedures that will save existing steel structures and protect new ones
from corrosion.

*	Jim Sharrow, Duluth Seaway Port Authority
*	Dave Bowman, U.S. Army Corps of Engineers (Detroit)
*	Steven Brossart, U.S. Army Corps of Engineers (Duluth)
*	Gene Clark, Wisconsin Sea Grant  
*	Chad Scott,  AMI Consulting Engineers
*	Dale Bergeron, Minnesota Sea Grant
*	Randall Hicks, University of Minnesota Duluth
*	Ted Smith, Marine Tech 

 

##

 

Adele Yorde

Public Relations Manager

Duluth Seaway Port Authority

1200 Port Terminal Drive

Duluth, MN  55802-2609 U.S.A.

218-727-8525

218-390-6973 (cell)

 

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