Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

FP5

EFESTUS Sintesi della relazione

Project ID: ICA3-CT-2002-10030
Finanziato nell'ambito di: FP5-INCO 2
Paese: Greece

A standardised method for producing degraded Cu-based alloys to be used for evaluating the effectiveness of conservation materials and methods

A new standardised method for producing degraded Cu-based alloys via an accelerated procedure based on chemical and burial treatments has been developed and optimised.

The starting Cu-based alloys are characterised by a chemical and metallurgical features similar to those used in ancient times and after the accelerated degradation process are characterised by a corrosion products structure i.e. the patinas, similar to those grown on archaeological artifacts.

These materials are not commercially obtainable and can be used for evaluating the effectiveness of conservation materials and methods as well as for anticorrosion studies.

The standardised method has been proposed on the base of the results achieved in the framework of the EFESTUS project. The results have shown that the bronze archaeological artefacts suffer of an intense and selective dissolution of copper that in many cases induce the formation of a stratified structure constituted by an external zone of Cu (II) compounds also enriched by the soil elements and an internal zone with a cuprous oxide layer (Cu2O) and a noticeable amount of copper chloride at the interface between cuprite and Cu-base remaining alloy matrix.

The role of the cuprite layer is considered acting as an electrolytical membrane allowing the transport of anions such as Cl- and O2- inward and cuprous ions outward. Indeed, the presence of copper chlorides in the archaeological artefacts indicates a noticeable transportation of chlorides from the soil trough the permeable corrosion product layers to the internal zone and remaining Cu-base matrix. The accumulation of chloride ions can be interpreted as an autocatalytic reaction that facilitates the oxidation of copper resulting also in an accumulation of chloride ions and in the formation of cuprite and cuprous chloride.

On the base of this information the method has been designed, optimised and tested and the corrosion products structure successfully compared with the corrosion products structure grown on the archaeological artefacts.

Informazioni correlate

Reported by

National Technical University of Athens, School of Chemical Engineering, epartment of Material Science
9, Iron Polytechniou Str.
15780 Athens
Greece