Civil war sub

By Mark Koenig

September 2017 - Technology has changed the way we live over the last century. In 1915, Alexander Graham Bell made the first coast-to-coast phone call. He predicted that, one day, calls “could be made without wires.”

According to Pew Research Center, nearly 95 percent of Americans now own a cell phone. Bell told the 1917 graduating class of McKinley Manual Training School that “the man of science will be appreciated in the future as he never has been in the past.”

I believe Bell was right. That’s why we took a bit of a departure from reporting on the latest in forming and fabricating methods and applications to bring you a cover story about H. L. Hunley, the world’s first combat submarine to sink a ship in 1864. We want to recognize those early ironworkers and the archaeology and conservation teams charged with rescuing Hunley and unraveling its mysteries.

We also want to hail the team at the Warren Lasch Conservation Center at the Clemson University Restoration Institute in North Charleston, South Carolina, for a technique they developed to treat salt-impregnated archaeological iron.

In commercial applications, corrosion-resistant coatings and plating methods shield steel from salt and saltwater. For museums and facilities like WLCC, conventional methods for subtracting chloride from iron artifacts have included electrolysis and immersion in alkaline water-based solutions.

In 2002, Dr. Michael Drews, then a professor emeritus of Clemson’s Department of Materials Science and Engineering, devised a way to treat Hunley’s iron artifacts with a process he had tested on textiles and other materials. In 2003, a major research effort launched a method to run subcritical experiments on archaeological iron at WLCC. The method had the potential to treat iron artifacts in a fraction of the time required by traditional methods.

Drews filed a U.S. patent on the treatment in 2006 and was awarded the intellectual property in 2011. In 2009, the WLCC designed and commissioned a subcritical reactor with a 1-ft.-wide by 2.5-ft.-long chamber suitable for big artifacts and batch treatment of smaller artifacts.

The process uses a diluted alkaline solution, heated to 350 degrees Fahrenheit and under high pressure, to extract embedded chloride ions out of metal.

The WLCC treatment  “rapidly and efficiently removes chlorides, converting iron corrosion products into their most stable forms.” A batch of test blocks took just seven days to treat.

Ian Macleod, former executive director for the collections management and conservation at the Western Australian Maritime Museum in Perth, Australia, has said, “I believe that this is the most significant advance in metals conservation in more than 80 years.”

In the true spirit of invention, the WLCC team thinks the process can be scaled up to treat larger pieces including ship hulls. While economics will govern scale-up, the first step could be a unit big enough to treat a cannon.

Technology has changed the way we live but projects like the conservation of the Hunley show us that technology also links us to the past and to the future.  FFJ

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