Measurement of Grain Boundary Corrosion Current on Copper [110]-Tilt Bicrystals by Scanning Vibrating Electrode Technique

Intergranular corrosion at [110] -tilt boundaries of high purity copper bicrystals was investigated in an acid solution using the scanning vibrating electrode technique (SVET). Anodic current peaks were observed at the grain boundaries. Cathodic current peaks were measured at small regions in the grain interiors quite adjacent to the Σ 9 (114) grain boundary. Laser micrographs obtained at the grain boundary showed that 10 μ m-wide terraced embankments parallel to the grain boundary are present extremely close to the V-shaped corrosion groove formed by the intergranular corrosion. This means that cathodic regions where electronation occurs are localized adjacent to the Σ 9 (114) grain boundary which was preferentially dissolved de-electronation site. On the contrary, little cathodic current peaks were observed at the vicinity of the Σ 3 (111) and Σ 11 (113) boundaries. These boundaries, especially the Σ 3 (111), showed lower corrosion susceptibilities, thus the amount of electron sink by de-electronation is relatively small at these boundary. This could explain the absence of cathodic current peaks at the vicinity of the grain boundaries.