Effect of soil parameters on the corrosion of archaeological metal finds

Archaeologists have observed an increasing tendency for freshly excavated iron artefacts to deteriorate due to accelerated corrosion. Iron artefacts and associated soil samples from German archaeological sites have therefore been examined and analysed. The approximate aggressiveness of the soil toward buried iron objects has been estimated by means of an existing rating standard. In addition, correlation coefficients have been calculated to investigate the relationship between soil properties and the state of corrosion. The results showed that the most heavily corroded artefacts came from sandy and acidic soils as well as from urban soils. The investigation showed that there is the risk of complete destruction of iron artefacts in well-drained soils with low buffering capacities. Conservation of the archaeological heritage requires the collaboration of soil scientists and metallurgists to develop suitable methods for the protection of buried artefacts.