Shop hull anodes at West Marine.
In boats, metal hardware, such as thru hull fittings, prop struts, and other metal parts, can be bonded and connected to a hull anode to provide protection against galvanic corrosion and stray electrical current. West Marine offers Martyr and Sea Shield hull anodes in a variety of shapes, sizes.
Stray Current Corrosion
Stray current corrosion in boats can occur when an unintended electrical current flows through the boat's metal components. This can happen when the boat's electrical system is not properly insulated, or when the boat is moored near an external source of electrical current, such as a nearby dock or marina. The current can cause damage to the boat's metal components, such as the hull, propeller, and shaft, by creating an electrochemical reaction that corrodes the metal.
When can galvanic corrosion occur?
Galvanic corrosion in boats occurs when dissimilar metals are in contact with each other and an electrolyte, such as salt water. Different metals have different galvanic potentials, and the metal with the lower potential will corrode preferentially. This can occur in boats when various components such as propellers, shafts, struts, rudders and thru hull fittings are made of dissimilar metals, such as bronze and stainless steel.
How Bonding Systems Work
Bonding systems typically consist of a zinc (for salt water), aluminum (for salt water or brackish water) or magnesium (for fresh water) hull anode that is thru bolted to the outside of the hull and which is connected to the boat's metal components through a series of copper wires. The bonding wires provide a low resistance path for stray current to pass to the hull anode where it is harmlessly dissipated. The anode also acts as a "sacrificial metal”, which corrodes preferentially to the boat's metal components, and thus protects them from galvanic corrosion.
Anodes must be periodically replaced.
It's important to keep in mind that the anodes need to be replaced periodically, as they will corrode over time. Also, the bonding system should be inspected regularly to make sure all connections are secure and clean.
Conclusion
In summary, bonding and connecting hardware to a hull anode through a bonding system provides protection against galvanic corrosion and stray electrical current by diverting stray current into the anode, where it is harmlessly dissipated, and by the anode corroding preferentially to the boat's metal components.