Most of the answers here are about applying something to the blade to protect it. I have been making scabbards that are self-oiling. Hollow out two pieces of wood ( I Like cedar ) so that the blade would rattle inside them then hot glue foam ( like old carpet padding ) to the insides. Then plane / band saw it level to the wood. Next hot glue felt to the inside edges of both pieces. And then to each other. Wrap the assembled scabbard with plastic packing tape. Lastly Sew a fabric / leather skin for it. And add oil to the insides. Results in a scabbard that is self oiling, protects the owner and is decorative. One of my swords has seen twenty years of service and looks like new. A neat thing is that you can hold it upside down and shake and it will not fall out. One failure was from the guy who left it on the tent floor during a cloudburst and it was 4 inches underwater.