In this research we observed surface compositional waves developing during galvanostatic electrodeposition of Au-Cu alloys from cyanocomplex solutions. Our study was carried out by synchrotron-based scanning photoemission spectro-microscopy. Scanning electron microscopy and X-ray diffraction analyses complemented the sample characterization. We found that the compositional wavefront developing between two homogeneous regions with different Cu enrichment consists of a progressive localization of Cu, initially at the crystallite boundaries and eventually in the formation of Cu-enriched crystallites. (c) 2008 The Electrochemical Society.