I think that is what tends to happen to blades that get used all the time in environments like that. I know I had a shotgun that had no bluing on the barrel. It would start to look a little reddish and I would hit it with a scotch brite pad and good to go. Later on sometime down the line I would see it agin, same thing, and just a VERY thin layer of oil on a different pad after removing the rust with the first one. The barrel actually got a sort of satin finish to it and finally got THAT patina and rust wasn't really a problem ever again.

You might get in the net and see if you can find a collins & co machete, get one and see what happens. Who knows, you may get lucky! Oh and I LOVE the taste of Cane when you just cut it and then chew on it. YUMMY!

When I was stationed in the Philippines and started living off base, our house was on the edge of a SEVERAL Hectar cane field and we got it all the time.