CATHODIC BONDING SYSTEM
The cathodic bonding system is often misunderstood and confused with other systems such as electrical grounding or lightning protection. While these systems may use the same conductor (under the condition that all the requirements concerning conductor size are met for each system), their functions are different.
Today we will take a closer look at the cathodic bonding system and its role. As we know, galvanic corrosion requires cathode and anode submerged in a common electrolyte and connected by a conductive path. Cathodic bonding conductor creates the path for electrons to travel from the sacrificial anode to the cathodes, which are the boat’s underwater metals (e.g., thru-hulls, shafts, propellers, etc.). Because the bonding conductor creates a galvanic cell it must be connected to the sacrificial anode, otherwise, the least noble metal will act as an anode. The wire used as a cathodic bonding conductor should be at least #8 AWG (or #6 AWG if a lightning protection system is installed on the boat) and it must be oil-resistant, insulated, tinned, stranded copper wire, or uninsulated copper strip. Copper braid or copper tubing is not acceptable for this purpose. Wiring connections shall be made without damage to the conductors so commonly seen hose clamps used for attaching bonding conductor to seacocks are not appropriate for this application. The quality of electrical connections is critical for the performance of a cathodic bonding system. If you want to test if underwater metals receive enough protection, you can measure resistance between the anode and protected metal (e.g., thru-hull). An electrical resistance greater than ONE ohm will degrade cathodic protection system performance.