Abstract
Bronze surfaces suffer from corrosion processes if they are exposed outdoors. They are affected by the presence of different aggressive species, the alloy composition and surface preparation. Bronze can be exposed outdoors non-protected or can be pretreated in different ways. Artists use chemical patinations in order to achieve visual effects. In the present study, different finishes were tested on three different patinas: green nitrate, green chloride and an electrochemically prepared patina. The tested finishes were: imidazole and benzotriazole type inhibitors in either ethanol or Paraloid B44, and Carnauba wax as a representative of waxes. The effectiveness of the applied finishes was examined by electrochemical impedance spectroscopy in a solution simulating urban acid rain. Aging experiments were performed in a climatic chamber and a salt spray chamber in order to combine different exposure conditions, the presence of sulphur dioxide, high humidity and a mist of chloride ions. After immersion in an urban acid rain solution, acidified to pH 5, the different patinas were investigated by SEM/EDX and Raman spectroscopy.
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