Launched in 2019 by a team of researchers, the SOS project – Save Our Shipwreck, “Save our wrecks” – aims to understand the corrosion mechanisms that degrade metal wrecks. Once these mechanisms have been identified, protocols for combating this corrosion can be established.
An unknown heritage
Why protect wrecks from corrosion? This is the first question that arises when discovering this project. We often ignore it, but wrecks are part of our cultural heritage. They are indeed recognized and protected by the UNESCO convention of 2001. Behind what is no more than a heap of wood or sheet metal lying at the bottom of the ocean hides a historical and ecological heritage. Beyond the tragedy that led to its sinking, a wreck represents over the years a great place of underwater life. Algae, fish, micro-organisms, flora… So many organisms that can attach themselves to this hard structure, unlike a sandy or muddy bottom.
A source of danger
“Wrecks are also ticking time bombs” emphasizes Lila Reboul, ccoordinator of the “SOS wrecks” program and project manager in the department of underwater and underwater archaeological research (Drassm). “Por some, they are full of their fuel. All the wrecks linked to major world conflicts are loaded with ammunition, explosive devices, chemicals.” Corrosion eventually eats away at the sheet metal, threatening to release all these dangerous products.
We must therefore find ways to delay this corrosion to maintain the structure of the wreck as long as possible. A process that includes several steps. The first: to assess the conservation of these wrecks. To do this, the SOS team did research on two of them, located in radically different environments.
One is off Dieppe, in the English Channel. It’s about HMS DaffodilA train-ferry type ship which was used to transport railway convoys and was shipwrecked in 1945 after being blown up by a mine. The other is in the Mediterranean, Lebanona shipwrecked in 1903 off the island of Maïre, near Marseille.
In 2020, on both wrecks, divers positioned metal plates and sacrificial anodes. What does this barbaric term mean? The principle of a sacrificial anode is to electrically protect ship hulls from corrosion by the exchange ofions. Dare metals active like zinc or magnesium are installed on the sheet. They easily corrode, “attract” corrosion and in a way “sacrifice” themselves in place of the structure that houses them, hence the name sacrificial anodes.
From October 2020 to March 2023, every six months, scientific divers have therefore come remove part of the device for analysis. Given their location, the wrecks should logically show different corrosion. The temperature of the water, its salinity, the currents, the proximity of a reef… So many elements which can vary the degree and speed of corrosion.
A long term project
At the end of May, the last sacrificial anodes deposited on the wreck of HMS Daffodil have been removed. A first analysis was presented on May 31 in Dieppe during a free entry conference. But the work of studying the various samples has only just begun. Eventually, this unique program in Europe (supported jointly by the ECATHE CNRSI’University of Pau and Pays de l’AdourTHE DRASSM and the company A-CORROS) wants to lead to very concrete actions.
The goal is that communities and national parks appropriate these methods which have an ecological and economic interest. Protecting these wrecks is indeed to attract a clientele of recreational divers but also to arouse the interest of the general public for this fascinating but little-known heritage.
A summer exhibition dedicated to the wrecks of the Alabaster Coast is also offered at the castle-museum of Dieppe until September 17, 2023. It presents the archaeological discoveries made on the wrecks located off the coast of Dieppe.