Titanium anode has excellent electrical conductivity and corrosion resistance, and its service life is much longer than that of lead anode. It can work stably for more than 4000 hours and has low cost. It will be an inevitable trend in the development of electro-galvanized and tin production at home and abroad. Titanium electrodes are currently used in Japan, the United States, Germany, and China, which not only greatly saves electroplating energy consumption, but also creates conditions for the production of thick galvanized and tin steel plates because it can increase the electroplating current density.
Titanium anode classification:
1. It is distinguished according to the gas evolved in the anode during the electrochemical reaction. The chlorine evolution anode is called the chlorine evolution anode, such as ruthenium-coated titanium electrode: the oxygen evolution anode is called the oxygen evolution anode, such as iridium-coated titanium electrode and platinum titanium mesh. /board. Chlorine evolution anode (ruthenium-coated titanium electrode): The electrolyte contains a high content of chloride ions, generally in the environment of hydrochloric acid, electrolysis of sea water and salt water. Corresponding products of our company are ruthenium iridium titanium anode, ruthenium iridium tin titanium anode.
2. Oxygen evolution anode (iridium-coated titanium electrode): The electrolyte is generally a sulfuric acid environment. The corresponding products of our company are iridium tantalum anode, iridium tantalum tin titanium anode, and high iridium titanium anode.
3. Platinum-coated anode: Titanium is the base material. The surface is coated with platinum, the thickness of the coating is generally 0.5-5μm, and the size of the platinum and titanium mesh is generally 12.5×4.5mm or 6×3.5mm.
Ruthenium, iridium, titanium anode has a certain working life during the electrolysis process. When the voltage rises very high and there is actually no current through, the ruthenium-iridium-titanium anode loses its function. This phenomenon is called anode passivation.
There are several reasons for the passivation of ruthenium iridium titanium anode:
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 coating and the substrate are not firmly bonded, they will fall off the titanium plate substrate and fall off. 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 dissolved
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 a layer of oxide film, which can increase the binding force of the active coating of ruthenium, iridium, titanium and the titanium substrate, make the coating firm, prevent ruthenium from falling off and dissolving, but 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 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.
D. There are cracks in the coating
During electrolysis, new ecological oxygen is generated on the ruthenium-iridium-titanium anode, part of which discharges at the interface between the active coating and the electrolyte, and then leaves 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 falls 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.