Did anyone catch the show about Caligula's pleasure ships?
It was on the History Channel last week. The technology aboard those craft was thought to be unknown to the Romans. To stop corrosion, the iron nails were copper coated. Seems the Romans used an electrolytic process to do it. They also found ball bearings, and a water spigot with a design nearly identical to ones we use today. If it comes on again, I highly recommend it.