Experimental studies have been carried out with ribbon cobalt electrodes in buffered phosphate solutions of different concentration and pH under potentiostatic control. Bistable as well as oscillatory behavior have been observed in the system. The visible fronts which occur in both bistable and oscillatory conditions undergo acceleration. The Flade potential and the dissolution time of the passive layer as a function of potential and pH have been determined and have been related to the spatiotemporal behavior of the system