For protecting a cathode block surface and a whole electrolyzer lining it is proposed to use boron and titanium compounds in the form of an active substrate of their carbides (TiC and B4C) that under successive electrodeposition conditions with transformation and reaction transitions create a layer wettable with aluminum. Combined synthesis processes are studied for wettable coatings and the mechanism of carbide formation on carbon cathode surface layers. Possible processes of aluminum carbide formation with its transition into carboxide surface substances are suggested for discussion.