By Warren Lasch
When Senator Glenn McConnell asked me to serve as Chairman of Friends of the Hunley in 1996, I had no idea where that path would take me. Over the next nine years, I became immersed in the project, learning not only the amazing history of the Civil War submarine, but also much of the science behind preserving an iron vessel that had spent more than 130 years submerged in salt water and silt.
Salt water will preserve iron as long as the material remains submerged, and silt further protects it. As soon as iron makes contact with air, however, the rapid process of oxidation begins. In some cases, when salvagers have removed old cannonballs from the sea, they have spontaneously combusted because of the heat associated with rapid oxidation. Metal shavings from some rivets on the Hunley became so hot they burned through the plastic bags containing them.
Another problem following iron preservation in saltwater is the chloride penetration. While in the water, the chlorides penetrate the metal. When removed from the water and exposed to air, those chlorides crystallize and expand the iron’s surface, causing it to flake away.
In order to remove the chlorides from the Hunley’s metal, conservators placed the submarine in a 55,000-gallon bath of chilled fresh water, where they desalinated the iron using electricity. According to Paul Mardikian, the Hunley’s senior conservator, without this process, the Hunley would have reverted to a pile of iron flakes shortly after its excavation.