A Comparative Study of Copper Corrosion Products Formed at Two Hot Spring Sites
Authors: Masamitsu Watanabe, Masaaki Takaya, Morihiko Matsumoto, Jun'ichi Sakai Company: Nippon Telegraph and Telephone East Corporation (NTT-EAST) and Waseda University Date Published: 1/31/2016
Abstract: Corrosion products that formed on copper exposed at two hot spring sites with different H2S concentrations were analyzed. Several analytical techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES) were used to compare the corrosion products. The main corrosion products that formed on copper were mixtures of Cu2O and Cu2S. XPS analysis revealed a difference in the chemical state of the copper in the uppermost surface region of the corrosion products. Surface observation by SEM showed cracking and flaking of the corrosion products. These common features can explain the higher corrosion rates at hot spring sites. Elemental depth profiling analyses revealed that sulfur and oxygen coexisted throughout the corrosion products. An increase in the average H2S concentration resulted in the formation of Cu2S-rich corrosion products. This agreed well with the thermodynamic calculation results. The formation of Cu2S at a low H2S concentration can possibly be explained by the aggressiveness of the hydrogen sulfide ions that originated from the H2S dissolution.
Copper, Hydrogen sulfide (H2S), Corrosion products, Cu2O, Cu2S, Hot spring area, Harsh environment