The ICCP (Impressed Current Cathodic Protection) system is an advanced corrosion protection method widely used on modern seagoing vessels. It works by applying a controlled DC current to make the ship’s hull act as a cathode, thereby preventing electrochemical corrosion in seawater environments.
1. Principle of Metal Corrosion in Water
1.1 Electrochemical Corrosion
In seawater (a strong electrolyte), metal surfaces with higher electrical potential become anodes and corrode first, while those with lower potential become cathodes and are protected.
1.2 Sacrificial Anode Method
Traditionally, zinc (Zn) plates are attached to the ship’s hull. Since Zn has a lower potential than iron (Fe), it corrodes in place of the hull, acting as a sacrificial anode.
2. ICCP System – Cathodic Protection with Impressed Current
2.1 Working Principle
Unlike the sacrificial anode method, the ICCP system uses a controlled DC power supply to force current to flow from impressed anodes to the ship’s hull, keeping the hull permanently cathodic and protected from corrosion.
2.2 Advantages of ICCP
- Provides stable and continuous hull protection.
- Reduces maintenance costs – no frequent anode replacement.
- Automatically adapts to environmental conditions.
3. Components of the ICCP System
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Component
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Description
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Impressed Current Anodes
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Installed on the outer hull; typically made of MMO (Mixed Metal Oxide).
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Reference Electrodes
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Monitor the potential of the hull to regulate output current.
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Shaft Earthing & Rudder Bonding
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Ensure complete protection of propeller shaft and rudder.
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DC Power Supply Unit
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Automatically regulates voltage and current based on hull conditions (Auto/Manual modes).
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4. Crew Responsibilities for ICCP Operation
To maintain the system’s effectiveness and safety, crew members should perform the following tasks:
- Maintain ICCP Logbook: Record voltage, current, and system status regularly as per the company’s procedure.
- Perform Periodic Inspections: Photograph and report the condition of cable connections inside the hull to detect any signs of seawater leakage.
- Operate the Control Unit: Understand how to switch between Auto and Manual modes on the DC power controller.
- Freshwater Navigation Precautions: ICCP becomes less effective in freshwater due to high electrical resistance. In Auto mode, the system may increase voltage excessively, leading to faults. Therefore:
- Monitor the ICCP system closely in freshwater.
- Follow manufacturer guidelines or switch to Manual mode if needed.
5. Conclusion
The ICCP system is essential for protecting a vessel’s hull from corrosion. Understanding its working principle, components, and proper operation helps extend hull life, reduce maintenance costs, and ensure maritime safety.
BBC – SMR Marine
Training Department
Capt. Dang Quang Dan (+84 0948 067 095)
