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Keywords:

  • bronze;
  • chemical patina;
  • nitrate patina;
  • chloride patina;
  • Raman spectroscopy

Patinas form spontaneously on copper and high copper alloys when exposed to humidity and air. They usually protect the underlying metal from corrosion. Bronze is often chemically patinated by artists to achieve an antique appearance. However, in the case of chemical patinations on bronze, there is a lack of studies about their change over time during exposure to different types of environments.

Recent types of bronze, brown patina and two green type patinas (green chloride and green nitrate patina) applied over a brown patina, were selected for testing. The aim of the present study was to monitor the transformation process of chemically formed patinas and of the bronze itself after exposure to simulated urban acid rain, for a period of 35 days. The structures of the patina and corrosion products were characterized by scanning electron microscopy (SEM) and Raman spectroscopy.

Three differently coloured patinas were scraped off from the bronze statue of the poet France Prešeren, two green type patinas and one brown type, to predict the probable influences of the environment, the base alloy and previously used patination techniques. Copyright © 2012 John Wiley & Sons, Ltd.