Investigation of copper patinas using ion beam analysis and scanning electron microscopy

Abstract

Ion beam analysis (IBA) techniques were applied successfully to the investigation of non-corroded and artificially corroded patina layers grown on copper substrates in order to explore their potential use in the study of degradation phenomena of copper and copper alloys subjected to chemical treatment and exposed to selected environmental conditions. Rutherford backscattering spectroscopy (RBS) with deuterons as projectiles and the nuclear reactions 16 O(d,p) 17 O and 32 S(p,p g) 32 S were applied to the investigation of the depth distribution of oxygen and sulphur in near-surface layers of synthetic patina consisting of mineral phases corresponding to chalcanthite as well as to cuprite + chalcanthite and antlerite + brochantite + chalcanthite. Electrochemical techniques (potentiodynamic polarization and cyclic voltammetry in 0.5 M Na 2 SO 4 ) were used for artificial acceleration and study of the corrosion processes, and scanning electron microscopy (SEM/EDS) was used for examination of the surface morphology of the samples. A patinated roof sample from the Vienna Hofburg also was investigated using the same techniques. The measurement showed that IBA can provide valuable information for the study of patina near-surface layers of thickness up to a few micrometres and indicated that cuprite was the mineral phase primarily formed on the copper substrates and the main component of the interface between the patina layer and the metallic substrate. The investigated copper patinas looked rather heterogeneous and were characterized by high porosity. Mixed patinas exhibited considerable stability to further corrosive attack.

Novel Procedure for Brochantite Based Pigment Production and Its Immobilization for Restoration of Historical Copper Objects

“…Via metastable basic salt, the patina is transformed into final corrosion products based on sulphate (brochantite) or chloride (atacamite) [1,3,12]. The kinetics of patina formation are dependent on pollutant concentration in the atmosphere [6,[13][14][15][16][17][18]. If the pollutant concentration is not sufficient, the patina based on oxides remains black [5,12,[19][20][21].…”