Electric current will flow from the anodic areas into the electrolyte as the metal corrodes.
Gold was particularly valued as a metal that would not rust, tarnish, corrode or otherwise grow corrupt.
The sacrificial metal then corrodes instead of the protected metal.
It's caused by having more than one kind of metal in saltwater, corrodes the metal.
In other words, the underlying metal will strongly corrode before the protective passive film is reformed, if at all.
You take it for granted that metals corrode, coastlines change, and storms interfere with communication.
When immersed separately, each metal corrodes at its own rate.
All metals, apart from pure gold, will corrode naturally when exposed to elements such as air.
But any metal anywhere near Nobby's skin corroded very quickly.
But the shape of the revolver was clear to see, the metal now corroded, the wood quite rotten.