Multianalytical study of patina formed on archaeological metal objects from Bliesbruck-Reinheim

Patinas naturally formed on archaeological bronze alloys were characterized using light microscopy (LM), micro energy dispersive X-ray fluorescence an alysis (mu-EDXRF), time of flight secondary ion mass spectrometry (TOF-SIMS ) and scanning electron microscopy in combination with energy dispersive X- ray microanalysis (SEM/EDX). The examinations carried out on cross-sections of samples have shown that in all samples the copper content in the corros ion layer is lower than in the bulk, while an increase of tin and lead coul d be observed. Two different types of corrosion were found: first type, a c orrosion formation leading to a three layer structure was observed on lead bronze. The outer layer consists mainly of Cu(II) compounds and soil materi al, followed by a fragmented layer of cuprous oxide and the surface layer o f the alloy, where a depletion of copper and an enrichment of tin and high amounts of Cl could be detected, The second type of corrosion is characteri zed by a two layer structure on the tin bronze sample consisting of an oute r layer with copper containing corrosion products and a layer with cracks, which reveals a depletion of copper whereas tin and lead are enriched. Also high amounts of Si were detected in this surface layer.