MICROMORPHOLOGICAL STUDY OF SELECTIVE DISSOLUTION OF Cu FROM CuPd-ALLOYS.

The selective corrosion of a series of CuPd-alloys has been studied by transmission electron microscopy. A special specimen preparation has been applied to avoid surface segregation of palladium and other surface layers. This investigation was carried out in the low current region as well as in the region above the critical potential of selective corrosion. In the latter case the typical morphology of selective corrosion, as observed by other authors, was confirmed. A quite similar, yet less pronounced corrosion attack was, however, detected in the low current region. As revealed by dark field microscopy, apparently unattacked parts of the surface were covered with Pd-crystallites. These crystallites as well as the dissolution nuclei were crystallographically orientated along low-indexed directions.