Henry VIII's warship, Mary Rose, is under threat from the sulfur and iron contained in its wooden frame.

After surviving over 400 years on the seabed, the remains of Henry VIII’s warship, Mary Rose, are now under threat from the sulfur and iron contained in its wooden frame, report European researchers.

Mary Rose-250

Source: © PNAS

Wooden gun shield remains from Mary Rose, showing salt formation on surface.

The Mary Rose was Henry VIII’s principal warship, before it was sunk by the French off the coast of Portsmouth in 1545. The wreck was not discovered until 1971 and was subsequently salvaged in 1982. The threat posed to the wreck from sulfur is that sulfur can oxidise to form sulfuric acid, especially in the presence of iron, and this can attack wooden timbers.

The researchers, led by structural chemist Magnus Sandstr?m, from the University of Stockholm, Sweden, analysed various samples of the hull and gunshield using x-ray photoelectron spectroscopy, x-ray fluorescence line scans and elemental analyses. The team discovered that sulfur accounted for about one per cent of the mass of the samples, so the wreck as a whole contains around 2 tons of sulfur. Sandstr?m’s team also detected various concentrations of iron, mainly close to cracks and bolt holes.

Research now focuses on how best to protect the Mary Rose from further damage. One possible method, which the researchers are testing with a similarly-affected 17th-century Swedish warship, is to remove the iron particles by enclosing them in a chelate cage, which prevents the iron from catalysing the formation of sulfuric acid. Jon Evans