Chris J. over at Grynx helpfully recounts the tale of his friend's water-damaged router and the steps he took to get it working again, if not perfectly. Basically this rescue mission involves complete disassembly of the affected device, rather counterintuitively running the circuit boards under more water, and using an alcohol-based cleaning agent (not gasoline, warn several commenters) to brush the remaining rust/calcium residue from the guts. Money quote from the article: "If the substance is already dry, as it was for me, then use your wife’s toothbrush (you don’t want to use your own, right?) to brush off as much as possible."