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What is a titanium anode? The full name of a titanium anode is a Titanium-based Metal Oxide Coated Anode (MMO), also known as a KSA anode (Dimensionally Stable Anode). It consists of a titanium substrate with a noble metal coating, providing excellent electrocatalytic activity and conductivity.
Titanium anodes can be classified based on the gas evolved at the anode during electrochemical reactions. Anodes that evolve chlorine gas are called chlorine-evolving anodes, such as ruthenium-based coated titanium electrodes. Anodes that evolve oxygen gas are called oxygen-evolving anodes, such as iridium-based coated titanium electrodes and platinum-coated titanium mesh/plate.
1. Chlorine-evolving anodes (ruthenium-based coated titanium): Typically used in environments with high chloride ion content, such as hydrochloric acid, electrolysis of seawater, and electrolysis of saline water, like ruthenium-iridium-tin-coated titanium anodes.
2. Oxygen-evolving anodes (iridium-based coated titanium): Generally used in sulfuric acid environments. Examples of our company's products include iridium-tantalum anodes, iridium-tantalum-tin anodes, and high-iridium anodes.
3. Platinum-plated anodes (platinum-coated titanium mesh/titanium plate): The titanium acts as the substrate, and a precious metal, platinum, is plated on the surface. The thickness of the platinum coating is typically 1-5 μm (micrometers). The specifications for the platinum-coated titanium mesh usually range from 12.7 * 4.5mm or 6 * 3.5mm.
Currently, domestically produced titanium anodes are mainly brush-coated. These electrodes have a wide range of applications and are also known as DSA (Dimensionally Stable Anodes). Titanium anodes exhibit the following advantages over similar anodes:
Stable Anode Dimensions: The electrode spacing remains constant during electrolysis, ensuring stable operation under constant voltage conditions.
1. Low Working Voltage: Titanium anodes have low energy consumption, reducing DC power consumption by 10-20%.
2. Long Service Life and Corrosion Resistance: Titanium anodes have a long lifespan and exhibit strong corrosion resistance.
3. High Purity of Metal Products: They overcome the dissolution issues associated with graphite and lead anodes, preventing contamination of electrolytes and cathode products, resulting in higher metal product purity.
4. High Current Density and Efficient Production: Titanium anodes exhibit high current density, low overpotential, and excellent electrode catalytic activity, resulting in efficient production.
5. Prevention of Short Circuiting: Titanium anodes eliminate the problem of short-circuiting caused by deformed lead anodes, thus improving current efficiency.
6. Easy to Shape and Achieve High Precision: Titanium anodes are easy to shape and can be highly precise.
7. Reusability of Titanium Substrate: The titanium substrate can be reused.
8. Lower Overpotential: The electrode surfaces and bubbles between the electrodes are easily eliminated, effectively reducing the electrolytic cell voltage.
Electrodeposition is a method that uses the reduction of metal ions in an electrolyte that has been leached and purified to obtain pure metal. It consists of a Ti base, a noble metal and/or noble metal oxide electrochemically active layer coated on it.
In electrometallurgy, titanium anodes can replace conventional lead alloy anodes and reduce voltage and energy consumption under the same conditions. For example, the electrolytic production of zinc has traditionally used lead alloy anodes containing small amounts of silver, antimony, or calcium. However, issues such as unstable dimensions of lead alloy electrodes, high oxygen evolution potential (approximately 800mV), corrosion during anode polarization, and lead ion dissolution and deposition on the cathode, resulting in zinc contamination and compromised product quality, have arisen. Titanium anodes can overcome these drawbacks of lead alloy anodes and are suitable for high-current density and narrow electrode spacing electroplating conditions. They are not only suitable for sulfate systems but also for chloride systems and mixed sulfate-chloride systems.
By applying different coatings, the conductivity and electrocatalytic activity of titanium anodes are enhanced, promoting electrolytic reactions and extending the anode's lifespan in various usage environments, achieving the desired performance.
Thickness of Metal Oxide Coatings on Titanium Anodes:
The primary role of the coating is to enable electrocatalytic reactions with the noble metal content meeting the usage requirements to ensure the normal operation of the anode product. The thickness is merely a superficial characteristic determined by the number of coating layers and the concentration of the solvent, and it is not directly related to the content of noble metals. Excessive coating thickness can actually lead to easier detachment.
1. Technical Characteristics: MMO titanium anodes exhibit excellent antibacterial and corrosion resistance properties, a long electrode lifespan, and can operate at high current densities with high efficiency. The operating current density of 10,000 A/m² is attributed to an oxygen-evolving anode based on industrial pure titanium.
2. High Catalytic Activity: Platinum-coated electrodes are known for their high overpotential for oxygen evolution (1.563V vs. Hg2SO4), while MMO anodes have a lower overpotential for oxygen evolution (1.385V vs. Hg2SO4), making it easier for the anode to evolve oxygen. Therefore, the cell voltage is relatively lower during electrolysis, resulting in energy savings. This phenomenon has been evident in the treatment of alkaline copper plating baths behind copper foil.
3. No Pollution: MMO coatings are stable oxide coatings, and the anode coating is a ceramic oxide of the noble metal iridium. It is almost insoluble in any acid or alkali. The overall oxide coating thickness is approximately 20-40 μm, which means that MMO anodes do not contaminate the plating bath. This characteristic is similar to platinum-coated electrodes.
4. Cost-Effectiveness: MMO anodes are approximately 80% of the cost of platinum-coated electrodes. MMO electrodes exhibit superior electrochemical stability in alkaline copper electroplating baths and provide the same lifespan as platinum-coated electrodes (with a 3.5 mm coating thickness). They also possess excellent electrolytic activity and durability.
5. Presence of Chlorides in Sulfuric Acid Electrolytes: The use of dimensionally stable anodes prevents this phenomenon and allows the insoluble anode technology to achieve superior performance in such applications.
6. Minimal Anode Maintenance: There is no need to stop production for cleaning and anode replacement or re-plating. This leads to increased productivity and reduced manual labor.
7. Lifespan of Insoluble Anodes: The lifespan depends on the type, working current density, and contact with various electroplating chemicals. Due to the tendency of copper ions to accumulate rapidly at the edges of the holes (high current density regions) and much slower accumulation in the central parts of the holes (low current density regions), the distribution of copper deposition becomes highly uneven, resulting in the "dog bone" effect. Moderate current density operations result in the "dog bone" effect, while lower current density operations lead to cylinder cracking, and higher current density operations result in burning. This is a significant challenge for electroplated circuit boards. The use of platinum-titanium insoluble anodes in sulfuric acid electrolytes has led to the development of reverse pulse plating anodes. The presence of chlorides in this current environment causes platinum layers to peel off over time.
