Under-deposit corrosion in cast iron (Hurricane Sandy context)

Student-presented case (Brian). Graphitic corrosion of cast iron component exposed to seawater after Hurricane Sandy; the silicon-derived glassy passive film was breached by chlorides under deposits. Tom appends the "cleanliness is next to godliness" corrosion rule.

Student (Brian): So there's cast iron, which is iron with four percent carbon... [continues describing the case]. You take out the cast iron component and we cover the cross-section, look at it, and all you see is a spongy material. So what you were getting there was a graphitic corrosion. Very similar to — they check the alloy, they see with the acid, dezincification. But this is for cast iron. What happened was you had seawater, and so it was eating away at all the iron.