Weird indeed! However, if you suspect that it was submersed in salt water at some time, be very careful: some years ago, my son's steel Peugeot road bike blew into the dock at our marina. I managed to fish it out of 13ft of water, thoroughly washed it with fresh water and squirted WD40 into everywhere and everything I could reach. The bike hung unused in our garage for a couple of years, then one day I decided to take it down, got hold of the top tube and it crumbled in my hand! It was rusted completely through.