Condenser Cathodic Protection Technology and Applications
1. Condenser Introduction
The condenser is a kind of heat exchanger that condenses the exhaust steam of the steam turbine into water, also known as the condenser. According to the different ways of steam condensation, condensers can be divided into two types: surface type (also known as wall type) and hybrid type (also known as contact type). In a surface condenser, the vapor separated from the cooling medium is condensed into a liquid on the cooling wall (usually a metal tube). The cooling medium can be water or air. This article focuses on surface (partition) cathodic protection.
2. Corrosion of Condensers
The condenser pipes are mainly made of copper alloys, stainless steel, and industrial pure titanium. Different materials have different corrosion resistance characteristics. In practical applications, galvanic corrosion often occurs due to the mixing or contact of different metals, and poor cooling water quality can accelerate corrosion. Corrosion leads to premature equipment scrapping, production downtime, and significant losses in time and cost.
3. Condenser Cathodic Protection
Traditional coating protection for condensers is often ineffective because coatings are easily damaged or aged. Cathodic protection offers an effective, economical, and reliable method for corrosion control. It works by applying a cathodic current that reduces metal potential, preventing electron loss and oxidation.
Cathodic protection methods are divided into two types: impressed current and sacrificial anode. The impressed current method allows potential adjustment and has a long service life (up to 15–20 years with MMO anodes), while sacrificial anodes typically last 3–5 years.
4. Application Example: Unit 7 Condenser of a Power Plant
Unit 7 is a 100MW condenser unit using copper tubes (HSn-70-1A) with a cooling surface of 6815m². After only two years of operation, severe corrosion and leakage occurred. To solve this, impressed current cathodic protection was applied in combination with corrosion-resistant coating.
4.1 System Components
Potentiostat: Automatically controls current output.
Auxiliary Anode: Made of platinum-niobium, ensuring high discharge rate, low consumption, and durability.
Reference Electrode: Made of high-purity zinc for stable potential monitoring.
4.2 Corrosion Prevention Results
After implementation, corrosion of copper and carbon steel components was significantly reduced. The average corrosion rate of brass decreased by over 93%, and that of carbon steel decreased by about 74.8%.
The surfaces of protected samples remained smooth and free of pits, while unprotected samples exhibited severe localized corrosion. These results prove the effectiveness of the cathodic protection system.
5. Economic Benefits of Cathodic Protection
Cathodic protection is not just a surface treatment; it fundamentally stabilizes metal and prevents corrosion. The system reduces copper pipe leakage, improves feed water quality, and enhances boiler and steam performance. A 100MW unit using this technology can save significant annual costs by extending copper pipe life and avoiding unplanned shutdowns.
The one-time investment and annual maintenance cost (less than 18,000 yuan) are small compared with potential savings. Thus, the technology offers excellent input-output benefits and should be widely applied in power plant condenser systems.
6. Conclusion
Cathodic protection technology provides a reliable and efficient way to prevent condenser corrosion. Its combination with coatings ensures long-term stability, improved operational reliability, and significant economic advantages. It is a vital method for ensuring the safety and longevity of power generation equipment.
