Titanium anodes coated with mixed metal oxides (MMO) operate on a different basis than conventional galvanic anodes. They require the use of an external power source (potentiostat), which causes polarization of the anodes and the protected element.
The current generated in the potentiostat flows into the object from a titanium anode covered with MMO, which causes object’s cathodic polarization. As a result, corrosion processes are eliminated. The cathodic polarization of the protected object also causes local changes in pH within it, which leads to the precipitation of sparingly soluble compounds that seal the discontinuities of the protective coating (eg. enamel). This results in additional cutting off of the steel
structure from the corrosive environment.
Titanium anodes are characterized by stability and long life. They practically do not wear during the cathodic protection current generation process, because oxygen is generated on their surface. In general, these anodes can work for more than 10 years, while the estimated lifetime of a galvanic anode is about 2 years.
The most commonly used in cathodic protection, in particular drinking water tanks, are titanium anodes coated with MMO containing iridium and tantalum oxides.
MMO-coated titanium anodes are used in a variety of environments, including seawater, brackish water, sweetwater, coal powder and concrete.