The final stages of the salvage of the 16th century carrack Mary Rose on October 11, 1982. By the Mary Rose Trust, CC BY-SA 3.0

The Mary Rose, a 16th-century British warship, sank in 1545 off the south coast of England and remained there until she was salvaged in 1982. About 40 percent of the original structure survived, including over 19,000 artifacts and pieces of timber.

Researchers have been racing to prevent deterioration of the wooden structures since the ship was salvaged. While mired on the seafloor, sulfur-reducing marine bacteria migrated into the ship’s wood, producing hydrogen sulfide which then reacted with iron ions from corroded fixtures like cannons to form iron sulfides. When subjected to air above the sea surface, sulfur rapidly oxidizes in the presence of iron to form destructive acids.

A research team in the UK sought to avoid acid production by removing the free iron ions. The Mary Rose has been sprayed with solutions of polyethylene glycol for 30 years to lend structural integrity to the hull. The nature of the sulfur- and iron-based species along the core wood was evaluated by use of X-ray absorption near-edge spectroscopy, which also revealed a high content of oxidized sulfur on the wood surface.

These observations are being used to design a nanocomposite based on core magnetic iron oxide nanoparticles that include agents on their surfaces to affect ion removal. The nanoparticles can be directly applied to the porous wood structure and guided to particular areas of the wood using external magnetic fields, a technique previously demonstrated for drug delivery. A heat-responsive polymer will encase the nanocomposite to protect the nanoparticles and provide a way to safely deliver them to and from the wood surface. This method allows for the complete removal of free iron and sulfate ions from the wood, and the nanocomposites can be tuned by tweaking their surfaces.

Scientists from the University of Glasgow and the University of Warwick will present this research at the 256th National Meeting & Exposition of the American Chemical Society in Boston.