Factors Influencing the Long-term Corrosion of Bronze Artefacts in Soil

The investigation was undertaken to determine the main factors causing deterioration of bronze objects in soil by studying artefacts from archaeological excavations in progress. Objects that had been buried for 300–3000 years were examined. The composition of the metal, corrosion products, and surrounding soil was determined by chemical analysis. The possible effect of polluting sources and the environment in general was also taken into account. In total, 82 variables were coded, and their effects were statistically evaluated by multivariate analysis. Acidic soil, large deposits of sulfur pollutants in relation to the critical load, the presence of soot and soluble salt, and conditions giving access to water and air were found to accelerate the deterioration. A major part of the corrosion is likely to have occurred during the latest century. The results are of importance for the understanding and estimation of long-term corrosion of bronze objects in soil.