Reasons For The Failure Of Ruthenium Iridium Titanium Anode Passivation
The ruthenium-iridium-titanium anode has a certain working life during the electrolysis operation. When the voltage rises very high and there is actually no current passing through, the ruthenium-iridium-titanium anode loses its function. This phenomenon is called anode passivation.
Ruthenium iridium titanium anode passivation has the following reasons.
1) The coating peels off
The titanium ruthenium iridium titanium anode is composed of a titanium substrate and a ruthenium iridium titanium active coating. The electrochemical reaction is only the ruthenium iridium titanium active coating. If the coating and the substrate are not firmly bonded, they will fall off the titanium substrate and fall to a certain extent. To a certain extent, the titanium ruthenium iridium titanium anode loses its effect. (Divided into crushed peeling, belly-shaped layer peeling and cracked peeling)
2) There are cracks in the coating
During electrolysis, new ecological oxygen is generated on the ruthenium-iridium-titanium anode, some of which discharge at the interface between the active coating and the electrolyte, and then leave the anode surface to generate oxygen into the solution; due to cracks in the active coating, the other part of the oxygen is adsorbed on the anode On the surface, through the active coating through diffusion or migration, it reaches the interface between the coating and the titanium substrate, and then oxygen is chemically adsorbed on the surface of the titanium substrate to form a non-conductive oxide film (TiO2) with the titanium, resulting in reverse resistance; Or the electrolyte penetrates through the cracks of the coating, the titanium substrate is slowly oxidized, and the interface with the ruthenium-iridium-titanium active coating is corroded, causing the ruthenium-iridium-titanium active coating to fall off, resulting in an increase in the potential of the ruthenium-iridium-titanium anode. The increase in potential further promotes the dissolution of the coating and the oxidation of the titanium substrate.
3) RuO2 dissolves
Reduce the generation of oxygen, which can slow down the formation of oxide film. When the total current density of electrolysis increases, the increase in the rate of chlorine generation is much greater than the increase in the rate of oxygen generation, so the increase in current density is conducive to the decrease of the oxygen content in chlorine. The titanium substrate is pre-oxidized to form an oxide film, which can increase the binding force of the active coating of ruthenium, iridium, titanium and the titanium substrate, make the coating firm, and prevent the ruthenium from falling off and dissolving, but it will also cause ruthenium, iridium, titanium Increase in anode ohmic drop.
4) Oxide saturation
The active coating is composed of non-stoichiometric RuO2- and TiO2, which is an oxygen-deficient oxide. The non-stoichiometric oxide is the real active center of chlorine discharge. The more such oxides, the more active centers, and the better the activity of the ruthenium-iridium-titanium anode. The conductivity of ruthenium-iridium-titanium-coated anodes is the performance of distorted n-type mixed crystals generated from isomorphic RuO2 and TiO2 after heat treatment. There are some oxygen vacancies. When these oxygen vacancies are filled with oxygen, the The potential rises rapidly, causing passivation.
