a. 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 combination of the coating and the substrate is not strong enough, it will fall off the titanium substrate To a certain extent, the titanium ruthenium iridium titanium anode is useless. (Divided into crushed peeling, belly-shaped layer peeling and cracked peeling)
b. RuO2 dissolves
Reducing the occurrence of oxygen 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 first, 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 falling and dissolution of ruthenium, but it will also cause ruthenium, iridium, titanium Increase in anode ohmic drop.
c. Oxide saturation
The active coating is composed of non-stoichiometric RuO2- and TiO2, which are oxygen-deficient oxides. It is the non-stoichiometric oxide that really serves as the activation center of the chlorine discharge. The more such oxides, the more active centers, and the better the activity of the ruthenium-iridium-titanium anode. The conductivity of the ruthenium-iridium-titanium coating anode is the performance of the distorted n-type mixed crystal 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, leading to passivation.
d. 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, forming 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 active coating of ruthenium, iridium, titanium is corroded, and the active coating of ruthenium, iridium, titanium is peeled 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.