Biofouling Control in Seawater Cooling Systems
In power plants that use seawater as the cooling medium, the growth and attachment of marine organisms in pipelines, condenser tubes, and heat exchangers represent a long-standing operational challenge. This phenomenon, commonly referred to as biofouling, can significantly reduce heat transfer efficiency, increase hydraulic resistance, and compromise the long-term reliability of the cooling system.
To control marine biofouling, many facilities install seawater electrochlorination systems, which generate disinfectant directly from seawater through electrolysis.
In these systems, a low concentration of sodium hypochlorite (NaOCl) is produced on site and continuously dosed into the cooling water. The residual oxidant effectively inhibits the settlement and growth of marine organisms such as algae, mussels, and bacteria.
Compared with conventional chemical dosing methods, electrochlorination offers several operational advantages. Hazardous chemicals no longer need to be transported, stored, or handled in large quantities. Instead, disinfectant is generated on demand, improving plant safety while reducing chemical logistics and operational risks.
Key Components of a Seawater Electrochlorination System
A typical seawater electrochlorination system used in power plant cooling applications consists of several major components:
- Electrolyzer
- Rectifier
- Control system
- Piping and dosing system
- Installation and commissioning
With the continuous expansion of coastal power plants, desalination facilities, offshore platforms, and marine infrastructure, the global electrochlorination market has maintained steady growth in recent years.
Industry analyses suggest that:
- The global electrochlorination system market will reach USD 420–480 million in 2026
- It is projected to grow to USD 690–770 million by 2035
- The compound annual growth rate (CAGR) is expected to remain around 5–6%
Within the overall cost structure of an electrochlorination system, MMO titanium anodes typically account for approximately 10–25% of the total equipment cost.
Although they are not the largest cost component, anodes represent one of the most critical electrochemical elements in the system. The anode material system, catalytic coating composition, and manufacturing quality directly affect:
- Chlorine generation efficiency
- System power consumption
- Long-term operational stability
For this reason, the design and manufacturing quality of MMO coated titanium anodes play a decisive role in the reliability and service life of seawater electrochlorination systems.
Titanium Anodes for Seawater Electrolysis: Materials and Manufacturing Technology
In seawater electrochlorination systems, MMO (Mixed Metal Oxide) coated titanium anodes are widely used as the core electrochemical component responsible for chlorine generation.
These electrodes combine a corrosion-resistant titanium substrate with a highly active catalytic oxide coating, enabling efficient electrolysis of seawater while maintaining long-term durability.
Titanium Substrate Selection
Titanium is widely used as the substrate material due to its exceptional corrosion resistance in marine environments.
When exposed to seawater, titanium naturally forms a stable and dense oxide film on its surface. This passive layer protects the metal from corrosion even under highly saline and conductive conditions.
During electrolysis, the titanium substrate mainly functions as:
- A structural support for the electrode
- A conductive carrier for the catalytic coating
Commercially pure Grade 1 or Grade 2 titanium is typically used for seawater electrochlorination anodes.
Depending on electrolyzer design and hydraulic flow conditions, titanium substrates can be manufactured into different electrode configurations, including:
- Plate anodes
- Mesh anodes
- Tubular anodes
These structural designs help optimize current distribution and improve electrolyte flow patterns inside the electrolyzer, thereby enhancing overall electrolysis efficiency.
MMO Catalytic Coating System
To enable efficient chlorine evolution during seawater electrolysis, the titanium substrate is coated with a mixed metal oxide (MMO) catalytic layer.
This coating typically consists of platinum group metal oxides, such as:
- Ruthenium dioxide (RuO₂)
- Iridium dioxide (IrO₂)
- or proprietary mixed oxide formulations.
These materials exhibit excellent electrocatalytic activity and significantly reduce the overpotential required for chlorine evolution.
The MMO coating performs several essential functions:
- Increasing catalytic activity for chlorine generation
- Reducing energy consumption during electrolysis
- Maintaining stable electrochemical performance
- Extending the operational service life of the anode
In practical engineering applications, the composition and ratio of metal oxides are optimized based on operating current density, seawater composition, and electrolyzer design parameters.
Coating Preparation and Manufacturing Process
The performance and durability of MMO titanium anodes depend not only on material selection but also on coating technology and manufacturing process control.
A typical manufacturing process includes the following steps.
Surface Preparation
The titanium substrate undergoes mechanical treatment and chemical acid cleaning to remove surface oxides and contaminants. This process creates an activated surface that promotes strong adhesion between the substrate and the catalytic coating.
Coating Application
A precursor solution containing metal salts is applied to the titanium substrate using solution coating or slurry coating techniques, ensuring uniform distribution of the catalytic materials.
Thermal Decomposition and Sintering
The coated substrate is then subjected to high-temperature thermal decomposition, which converts the metal salts into stable metal oxides and forms a firmly bonded catalytic layer.
Multiple coating and thermal treatment cycles are typically required to gradually build a uniform, dense, and highly active catalytic structure.
The final coating thickness is generally 4 μm or greater, ensuring stable electrochemical performance during long-term operation.
Electrochemical Performance and Service Life
In power plant seawater electrochlorination systems, high-quality MMO titanium anodes typically provide:
- High chlorine evolution efficiency, reducing system energy consumption
- Uniform current distribution, ensuring stable chlorine production
- Excellent durability, with a typical service life of 5–10 years depending on operating conditions
- Low maintenance requirements, minimizing system downtime and replacement costs
Through the combined optimization of substrate materials, catalytic coating systems, and manufacturing processes, MMO titanium anodes enable reliable long-term operation of seawater electrochlorination systems in power plants and other marine industrial facilities.
Typical Applications of Seawater Electrochlorination Systems
Power plant cooling systems
Seawater desalination plants
Offshore oil and gas platforms
LNG terminals
Ballast water treatment systems