engleski

Investigation of deterioration of outdoor bronze sculptures

Clarification of corrosion phenomena occurring on outdoor bronze pieces of art is highly important for investigating possibilities of corrosion prevention in order to preserve the cultural heritage [1]. In this work, combined electrochemical and spectroscopic investigation of corrosion mechanisms and corrosion product layers formation on outdoor bronze sculptures was carried out. Binary Cu-6Sn bronze (94 mas.% Cu i 6 mas.% Sn) which is widely used for sculpture casting was taken as a reference bronze. Investigation of corrosion mechanisms in the first phase (30 days period) was done in three model atmospheric corrosive environments: rural, urban and marine environment [2]. Corrosion mechanisms were investigated using electrochemical techniques: cyclic voltammetry (CV), polarization resistance (Rp), corrosion potential (Ecorr), and electrochemical impedance spectroscopy (EIS). The surface layer morphology, composition and structure of corrosion layer products have been characterized by scanning electron microscopy (SEM) and analyzed by energy dispersive spectroscopy (EDAX), proton induced X-ray spectroscopy (PIXE) and attenuated total reflectance Fourier transformed infrared spectroscopy (ATR FTIR). Three different types of corrosion mechanism were proposed from the obtained results. To confirm results obtained from artificially corroded bronze sheets, two bronze artefacts with naturally formed patinas (i) patina from „Roman wheel” found near Zagreb, dating from the 1st century A.D. and (ii) patina originated from the „Zelenci“, Renaissance sculptures from Dubrovnik were investigated using EDAX and ATR-FTIR techniques.

Bronze; corrosion mechanisms; Corrosion and protection of outdoor bronze sculptures

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