I have read a lot about this and searched this forum for information but none seems to answer a specific problem. Old riveted steel butty, so no engine, propshaft or prop. There is no shoreline other than the occasional extension lead for 240v power tools or lights when working on the boat. No 12v battery on board. Not moored in a marina. No wiring, live or otherwise is earthed to the boat anywhere. Steel of the footings below the waterline are generally good but in certain parts, mostly toward the bows, after pressure washing off small mounds or rust and the jet black scab found underneath, there is bright silvery pitting. I understand this indicates strong galvanic and stray electrical current resulting in rapid erosion of the metal, usually to the point where there are no oxides present. But what on earth is the cause?. The only other clue is that where there is most pitting, is where it is moored up against a land surface water outfall which splashed down between the boat and the concrete wharf, when it rains.