Originally Posted by mikehhogg
POLY you go ahead and use graphite all you like but chemistry is chemistry and where aluminium is concerned graphite will accelerate the corrosion process. you don't have to be connected to shore power to be affected by stray currents in a marina,you just have to be tied up in there.Another thing I see people doing is using copper based antifoul on their boats ,yet again another accelerator in the corrosion process.The proof as I stated earlier is my fifty year old all aluminium de groot that has no traces of corrosion.Zincs from new and plenty of them, cleaned anodes regularly and kept as far away from Marinas as possible
If science is your argument you’ll need more than n=1 with no reference study to prove your point!
Graphite can only “accelerate*” the corrosion process if both the graphite and the anodic material are both immersed in the sea water and electrically connected. It’s as misleading to say that graphite (especially graphite encapsulated in a hydrophobic grease) is about to be the death of any boat as it would be to suggest that wiring on boats should not contain copper! (Or indeed gold plated electrical contacts)
There are theoretical ways that stray currents could affect your boat without being connected to shore power but they are somewhat odd situations and even less likely to happen on a typical rib installation (which won’t have metallic through hull skin fittings).
*accelerate is probably a misleading term here since the rate is proportional to the surface areas of the anode and cathode, the distance between them as well as the potential of the materials. In many cases changing materials will not result in a significant rate difference - because the other factors dominate. In a perfect storm such as direct contact between aluminium and graphite whilst under water could...