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Evolution of patinas on copper exposed in a suburban area |
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| Authors: | Masamitsu Watanabe Etsuko Toyoda Toshihiro Ichino Yasuhiro Higashi |
| Affiliation: | a Technical Assistance and Support Center, Nippon Telegraph and Telephone East Corporation, 4-10-23 Higashigotanda, Shinagawa-ku, Tokyo 141 0022, Japan b NTT Service Integration Laboratories, Nippon Telegraph and Telephone Corporation, 3-9-11 Midori-cho, Musashino-shi, Tokyo 180 8585, Japan c NTT Energy and Environment Systems Laboratories, Nippon Telegraph and Telephone Corporation, 3-1 Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243 0198, Japan |
| Abstract: | Copper plates were exposed under sheltered outdoor conditions for up to one year, starting in September 2001 in Musashino City, Tokyo, a suburban area. Following various periods of exposure, the patinas on the plates were characterized to investigate their evolution by using X-ray fluorescence analysis, X-ray diffraction, field emission scanning electron microscopy, and glow discharge optical emission spectroscopy. The difference in the roles of sulfur and chlorine in the early stages of copper patination were identified by analyzing the depth profiles of these two elements. Sulfur was found on top of the patina as cupric sulfates such as posnjakite (Cu4SO4(OH)6 · H2O) or brochantite (Cu4SO4(OH)6). Brochantite appeared only after 12 months of exposure. In contrast, chlorine was found on the surface after only one month of exposure. It gradually penetrated the patina as the exposure period lengthened, forming copper chloride complexes. Chloride ions accumulated at the patina/copper interface, forming nantokite (CuCl), which promoted corrosion. |
| Keywords: | A Copper B XRD B SEM B X-ray fluorescence analysis B Glow discharge optical emission spectroscopy C Atmospheric corrosion |
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