A method of producing a self-sustaining body of refractory boride from the group consisting of the borides of titanium, chromium, vanadium, zirconium, hafnium, niobium, tantalum, molybdenum and cerium. This body includes a refractory boride and a dried colloid from the group consisting of colloidal alumina, silica, yttria, ceria, thoria, magnesia, lithia, monoaluminium phosphate and cerium acetate and is obtained from a slurry of the refractory boride in one or more of said colloids by casting the slurry on a porous plaster layer, and drying the cast slurry by draining through the plaster, or by pressing/drying. Subsequently, the dried body is subjected to heat treatment to bond the refractory boride in the dried colloid. The bodies are useful as components of aluminium electrowinning cells.