I've noticed in some of the old artworks of sea captains that blackened steel 'japanned' smallswords were popular. At first, I wrote this off as perhaps nothing more than a "prop" given to the subject being painted for artistic purposes, but Annis comments that smallswords were indeed popular among the maritime folks. I was wondering aloud if the blackened steel was more rust-resistant, as other naval swords that were painted or tarred black. Here's a sea captain (with an interesting history) whose pic is in the National Maritime Museum. Note the blackened hilt. Click on his pic for a bigger view.