Regarding corrosion, I performed an experiment. I put Vaseline on my Swedish Firesteel rod, and slipped a heat shrink sleeve over it. I dunked the whole thing in a cup of salty water, let it sit there underwater for a few days, and then took it out and let it sit for awhile. I took off the heat shrink and didn't observe any corrosion. In fact, the Vaseline was still in tact. I was able to generate sparks from the rod without wiping the Vaseline off. In fact, the Vaseline seemed to promote longer burning sparks, somewhat like the magnesium in mischmetal promotes longer burning sparks.

If you're like me, you can't motivate yourself to spend $27 plus shipping for one Exotac STRIKER. So, there you have a poor man's solution for protecting your ferro rod if you so desire. A rubber band helps keep the heat shrink in place and can be tinder/fuel.