Abstract: A bipolar electrode for electrowinning aluminum or other metals by electrolysis of a molten salt electrolyte containing a dissolved compound of the metal to be won comprises an anodic and a cathodic surface which are both preserved during operation by dissolution of small amounts of a substance in the electrolyte which is capable of being deposited on either surface at a rate compensating the corrosion thereof during electrolysis. The anodic surface is for example cerium oxyfluoride and the cathodic surface cerium hexaboride, both surfaces being preserved by addition of cerium compounds, such as oxides, fluorides, hydrides etc. to the melt. The cathodic surface may also include titanium diboride on top of or together with cerium hexaboride.