Despite the high corrosion resistance of carbon reinforced concrete, the use of carbon resp. CFRP can lead to completely new corrosion problems. Carbon is electrically conductive and forms an electrochemical potential in aqueous media (and thus also in damp concrete). This potential is very high in common media compared to unalloyed and also stainless steels. When contacting carbon fibres with such steels, e.g. with built-in parts, anchors and dowels, there is – at least in theory – the risk of bimetal corrosion. This was examined in the project C3-V3.4 in the frame of the research initiative „Carbon Concrete Composite – C3“, the findings of which are to be presented here.