After more than 15 years of study, researchers from the University of Nebraska-Lincoln (UNL) (Lincoln, Nebraska) presented findings on metal corrosion of the USS Arizona battleship, sunk by Japanese bombers during the attack on Pearl Harbor on December 7, 1941. The research was presented in December at the USS Arizona Memorial (Honolulu, Hawaii), just after the 75th anniversary of the attack.
The team is currently comprised of two former professors and students at UNL: Don Johnson and James Carr, emeritus professors of mechanical and materials engineering, and chemistry, respectively, and Dana Medlin and John Makinson, both graduates of the school. The team says the knowledge gained by studying corrosion of the wreckage could help to prevent environmental hazards around the world.
“The significance is there have been many sunken ships on the west and east coasts of America and all around the world that contain fuel oil or might be navigation hazards,” says Johnson.
The project started in the late 1990s with Johnson’s vacation to Hawaii. He traveled to the island of Oahu and after seeing the Arizona, remarked on the potential effects of the corrosion rate on the ship’s hull. Fortunately, the U.S. National Parks Service (Washington, DC), which oversees the memorial, agreed to help fund the project.
Since then, the UNL team has been studying external hull corrosion and environmental effects on the ship. Data gathered led the team to develop a mathematical formula to estimate the corrosion rate based on the effects of water temperature, oxygen concentration, and thickness of concretion—a buildup of organisms such as algae and barnacles that develops on a vessel in water.
Johnson says the formula is named the Weins Number, after Bill Weins—a former professor of mechanical engineering at UNL. Weins was part of the research team until his death in 2001.
“[Concretion] creates a barrier, so oxygen access and resulting corrosion rate is somewhat lower,” Johnson says. “That's been a surprise, because concretion accumulation has very likely contributed to extended structural integrity of the ship. What we've found so far, with the Weins Number, we believe the ship is going to remain quite stable for the next 150 to 200 years.”
As a metallurgist, engineer, and veteran, Johnson says he particularly enjoyed being able to present data on the battleship during the 75th anniversary ceremonies.
“The fact that I could look at the Arizona and relate its history to the corrosion and some of the problems that exist out there right now has been a great experience and opportunity to serve the U.S. Park Service and other government agencies,” Johnson says.
In all, 1,177 sailors died on the ship during the attack. In addition to the human toll, the ecology around the U.S. base was also devastated by thousands of gallons of fuel that spilled into the water and eventually washed onto beaches. Even now, an estimated 500,000 gal (1.89 million L) of fuel oil remains submerged, slowly leaking from the wreckage.
For more information, visit news.unl.edu.