Characterization of naturally grown oxide layers on copper with and without benzotriazole by electrochemical and photoelectrochemical measurements

Frédérique Ammeloot (1) , Benoit Millet (1) , C. Fiaud (1) , Luc Robbiola (2) , Eliane Sutter (1)

1 ENSCP - Laboratoire de Génie des Procédés Plasmas et Traitement de Surface
2 TRACES - Travaux et recherches archéologiques sur les cultures, les espaces et les sociétés

The active corrosion of ancient artefacts (bronze disease) is linked to the presence of copper chloride underneath Cu(I) oxide formed at the surface of bronze. The properties of the Cu(I) oxide determine the mechanism of formation of the corrosion layer and their knowledge would to develop efficient stabilization treatments. The aim of our work is to characterize the structure and the electronic properties of Cu(I) oxide layers formed in different conditions (atmospheric and aqueous electrolyte) under opencircuit potential, using electrochemical and photoelectrochemical methods and SEM. Photoelectrochemistry allows the characterization the semiconducting properties of the passive layer and leads to a better knowledge of the nature of the electrode/solution interface and of the electrochemical reactions occurring at the oxide surface. Atmospheric Cu(I) oxide shows mainly p-type behaviour, whereas Cu(I) oxide layers formed at open-circuit potential by immersion in a NaCl solution were shown to exhibit p-type behaviour during the first hours of immersion and simultaneous n-p behaviour for longer immersion times. In the presence of benzotriazole added to the sodium chloride solution, the photoelectrochemical measu-rements revealed modifications of the semi-conducting properties of the Cu2O layer (duplex p-n layer from short immersion times) and showed that BTA makes the oxide layer more insulating. Results will be discussed in regards to the Cu(I) oxide role on the bronze disease.

Mots clés: semi-conductor; corrosion; benzotriazole; chloride; copper; photoelectrochemistry

Domaines: Matériaux

Frédérique Ammeloot, Benoit Millet, C. Fiaud, Luc Robbiola, Eliane Sutter. Characterization of naturally grown oxide layers on copper with and without benzotriazole by electrochemical and photoelectrochemical measurements. METAL 95: International conference on metals conservation, Sep 1995, Semur-en-Auxois, France. pp.109-117. ⟨hal-00975720⟩