All You Need to Know About MMO Coating Process

As a titanium anode manufacturer, we are well aware of our customers’ concerns about the performance and quality of titanium anodes. The core of titanium anode, MMO coating, is the key to determine its electrochemical performance and service life. This blog will bring you a deeper understanding of the titanium anode manufacturing process, especially mmo coating process, to reveal the secrets behind the excellent performance of titanium anode.

What is MMO Coating?

MMO Coating, known as Mixed Metal Oxide Coating, is a functional coating prepared by mixing a variety of precious metal oxides in specific proportions according to specific application requirements. Common metal oxides include RuO₂, IrO₂, Ta₂O₅, and so on. The combination of these metal oxides gives the MMO coatings superior electrochemical activity, enabling efficient and stable current discharge in an electrolyte environment.

MMO Coating Types

1. Ruthenium Metal Oxide Coating

Coating oxide: RuO₂ + IrO₂ + X
Main function: Chlorination Evolution
Characteristics: Ruthenium coatings are widely used in chlor-alkali, sodium hypochlorite generators, disinfection equipment, fruit and vegetable sterilizers, seawater electrolysis, cooling tower descaler, swimming pool chlorinator, etc. due to their excellent electrocatalytic activity and cost-effectiveness. It can catalyze the oxidation reaction of chlorine ion to produce chlorine gas (Cl₂) with high efficiency, and at the same time, it has low oxygen precipitation overpotential, which is suitable for electrolysis environment under high current density.

2. Iridium Metal Oxide Coating

Coating oxide: IrO₂+ Ta₂O₅+ X
Main function: Oxygen Evolution
Characteristics: Iridium-based coatings show high stability in strongly acidic and highly oxidizing environments, and are particularly suitable for harsh electrolytic conditions. Its high catalytic activity and corrosion resistance make it an ideal choice for high concentration of chloride ions. It is commonly used in cathodic protection, electrolytic copper foil, copper extraction from PCB electronic circuit boards, nickel extraction, continuous copper plate plating, ozone generators, etc.

3. Platinum Metal Oxide Coating

Coating Oxide: Pt + X
Main function: Hydrogen Evolution
Characteristics: Platinum-based coatings are known for their excellent hydrogen precipitation catalytic performance, which can efficiently catalyze the decomposition of water to produce hydrogen (H₂). Its low overpotential and high stability make it the material of choice for hydrogen production from electrolyzed water, fuel cells, electroplating and other fields.

In addition, other precious metals such as Cobalt, Tungsten, Nickel, Manganese, Palladium, Niobium, etc. can be added to the MMO coating.

What To Do about MMO Coating Process?

1. Material Preparation

Firstly, low iron and low oxygen Gr1 pure titanium is selected as the base material. According to the size requirements or design drawings provided by customers, laser cutting, welding and CNC machining is to ensure the dimensional accuracy and structural integrity of the titanium base material.

2. Sand Blasting

Sand blasting is an important step in the preparation of titanium anodes. Through sand blasting, the oxide skin on the surface of titanium substrate can be effectively removed, and the surface roughness can be increased at the same time. The rough surface helps to increase the contact area between the subsequent coating and the substrate, enhance the adhesion of the coating, and thus improve the performance and life of the titanium anode.

3. Acid Washing Treatment

The titanium substrate after sandblasting is put into 10% oxalic acid solution for acid washing for 2 hours. The purpose of acid washing is to convert TiO₂ on the titanium surface into titanium hydride TiH₂, thus further removing surface oxides and providing a cleaner surface for subsequent coating processes.

4. Alcohol Cleaning and Ultrasonic Cleaning

After acid washing, the titanium substrate needs to be thoroughly cleaned. It is first cleaned with alcohol to remove residual oxalic acid and other stains on the surface. Afterwards, the titanium substrate is placed in an ultrasonic cleaning machine, which utilizes ultrasonic vibration to completely remove any remaining microscopic particles and oxides from the surface, ensuring that the substrate’s surface is clean and free of contamination.

5. Coating Configuration

The coating solution is configured according to the customer’s specific application scenario, usage environment and lifetime requirements. The coatings are usually composed of compounds of precious metals (e.g. ruthenium, iridium, etc.), and the ratio and thickness of the coatings are precisely controlled to ensure that their performance meets the requirements. During the configuration process, the coating material needs to be fully dissolved and stirred well to ensure the uniformity and stability of the coating.

6. Coating

Roll and brush the configured coating solution onto the surface of the titanium substrate evenly. During the coating process, make sure the thickness of the coating is uniform to avoid localized over-thickness or over-thinness. Uniform coating helps to improve the electrochemical performance and durability of the titanium anode.

7. Drying Process

After coating, the coating is dried using a hair dryer or other heating device to evaporate the solvent, leaving only the precious metal coating. During the drying process, the temperature and time should be controlled to avoid cracking or peeling of the coating.

8. High Temperature Sintering

The dried titanium anode is put into a high temperature sintering furnace and sintered at a temperature of 450~500°C. The initial sintering time is about 10 minutes. During the sintering process, the precious metals in the coating will form a strong bond with the surface of the titanium substrate, enhancing the adhesion and conductivity of the coating.

9. Repeat Coating and Sintering

Repeat the coating, drying and sintering process until the coating solution is exhausted, depending on the coating thickness required. The last sintering time should be extended to 1 hour to ensure that the coating is fully cured and tightly bonded to the substrate. After sintering, the titanium anode is cooled naturally to room temperature.

MMO Coating Process Tips

1.Before MMO Coating, it must be ensured that the surface of titanium substrate reaches industrial-grade cleanliness standard, and oil, oxides and other impurities are thoroughly removed. When sandblasting, it is necessary to use professional equipment, strictly control the sandblasting pressure, angle and distance, to ensure that the uniformity of the surface sandblasting to ± 5% or less. At the same time, the particle size of the sandblasted particles should be stably controlled in the range of 60-80 mesh to ensure the formation of uniform microscopic roughness on the surface of the substrate and provide an ideal adhesion basis for the subsequent coating.

2. Throughout MMO Coating production process, the humidity must be strictly controlled to ensure that all parts of the process are kept away from moisture and humid environments. In particular, it is vital that the titanium anode is allowed to cool naturally to room temperature before the coating is applied. If the coating is applied without sufficient cooling, the surface of the coating will have uneven patterns and dull color, which will seriously affect the overall quality and performance of the product. Therefore, strict adherence to the cooling process is the key to ensure the quality of titanium anodes.

Conclusion

The key to assessing a titanium anode manufacturer’s level of expertise is to look at its ability to control the entire MMO Coating Process. As a titanium anode manufacturer with decades of experience in the industry, we have not only established a strict process control system, but also implemented ISO standardized quality management in every production process.

Our product line covers all types of MMO coated anode products, including but not limited to:MMO anode plate , MMO anode rod ,MMO tubular anode,MMO anode wire,MMO anode disc,MMO anode ribbon

as well as custom-shaped mmo anodes.

With advanced manufacturing technology and extensive application experience, we provide specialized electrochemical solutions for a wide range of industries:Cathodic protection systems,Industrial wastewater treatment,Electroplating, Chlor-alkali production,Hydrogen energy etc

We always insists on driving product upgrading with technological innovation, and ensures to provide customers with high quality titanium anode products with excellent performance and long service life through strict process control and continuous quality improvement and if mmo anode project, welcome to contact us freely.