Innovative Electrodes for HVDC Submarine Cables

The number of HVDC submarine cable connections is increasing around the world. In these applications, electrodes design is paramount for technical and economic feasibility. Cathode's design is kept as simple as possible, if bidirectional operation is not required, since reduction reactions do not produce corrosion of the material. The situation is completey reversed for the anodes submersed in seawater: in this case, the corrosion mechanism could provoke removal of surface material. For this reason, in order to ensure a sufficiently high life span, the anode is usually made of different and more expensive materials, like titanium rods, coated with layers of a noble metal oxide, such as platinum, or a mixture of several of them. Sometimes the seawater anodes are also immersed in materials based on transition elements, such as rare earths. In this paper, an innovative prototype design for seawater anodes, based on steel-reinforced concrete, is presented. An experimental comparison between steel and concrete-steel seawater anodes showing an important reduction of the corrosion phenomena is also presented and discussed in this paper. The basics of the electrodes' electrochemistry is also explained. These basic concepts have shown that the mainly critically of anodes is corrosion by oxidation. Finally, this paper reports some considerations on how to prolong the electrode lifespan of real electrodes as much as possible. © 2015 IEEE.