Cathodic protection is a method used to protect metallic structures from corrosion. In the case of a narrowboat, it involves the use of sacrificial anodes that are strategically placed on the hull of the boat. These anodes are made of a metal that is more reactive than the hull (such as magnesium in freshwater) and will corrode before the hull does.
When the boat is immersed in water, an electrolytic reaction occurs between the anodes and the metal hull. The anodes corrode and release electrons, which travel through the water and to the boat’s hull, thereby neutralizing any electrochemical imbalances that would have led to corrosion. This process is known as galvanic protection.
It is important to regularly monitor the condition of the anodes and replace them as necessary, as failing to do so can lead to accelerated corrosion of the boat’s hull. Additionally, it is important to ensure that the anodes are properly connected to the hull and that the electrical system on the boat is properly maintained to avoid any potential issues.
To reduce the possibility of corrosion, narrowboats should be fitted with a galvanic isolator (good) or isolation transformer (better) and the AC and DC circuits must be bonded correctly.