Is it better to use welding or bolts to fix anodes on hulls?
In relation to corrosion, the welding process (if the joint is done in the right way, with proper welding materials) is better than the bolt on method, because the latter often causes the formation of interstices, cracks and empty spaces.
For this reason pay attention to:
- The welding material – should be as noble or more than the base material in order to obtain a “small cathode/large anode combination” to avoid differences between the electric potentials of the joined metals, which could generate galvanic batteries and therefore corrosion (see gasoline tanks made of aluminum). So pay attention to the quality of the materials you choose. Remember: spending more on welding materials will let you spend less in fixing problems and damages.
- How to make the welding joints – they must be continuous, even, without empty spaces and cracks. It is recommended to remove slags or splashed drops. Never weld directly on the internal surface of the metal plates which are in direct contact with the sea water. Fix the ground clamp of the welding machine as near as possible to the point where the welding is done.
- Never fix welding machine ground clamp onto the outer planks. Check if the grounding cable and clamp rubber sheath are perfectly intact to avoid that any electrical contact with the boat structure may discharge stray currents through the hull into the sea.
When using bolts and nuts (fiberglass hulls), the threads should be greased to avoid rust formation. It is better to use bolts and nuts made of brass or stainless steel in order to improve the conductivity. In this case you can place a rubber or plastic insulating backing pad between the anode and the hull (the current will pass only through the bolts and nuts). Make sure that the bolts are properly connected to the wiring grounding circuit.