Influence of seawater and its aerosols on copper patina composition

X-ray diffraction analysis was used to monitor patina composition on copper samples exposed during one-year period to different seawater zones (splash, tidal and full immersion) and marine atmospheric aerosols. Two phases contributed most to patina formation: cuprite (copper oxide) and atacamite (copper chloride compound). Their relative XRD spectra intensities were very similar in patina formed in the tidal sea zone, but atacamite became the sole majority phase in the full immersion zone. The cuprite phase decreased over time, and two minority copper sulfates phases appeared: posnjakite and chalcanthite (CuSO4). The results revealed that copper patina composition is strongly influenced by chloride pollution and specific zone conditions. Additional factors, such as wind-blown sand, continuous dredging in coastal areas and vessel docking, influenced degree of pollutant compound adherence to patinas and consequently their structure (porous or compact). (C) 2012 Elsevier B.V. All rights reserved.