Hey Guys...
Although the plastic sleeve will work to a certain degree, the cluprit with the corrosion of the ferrocerium is moisture and oxygen.
You need a physical barrier to protect the ferrocerium from exposure. Over the short term, it's niot going to be a problem. I use my rods all the time,, and keep a constant eye on them.. The ones I don't use I paint..
If you aren't going to use your ferro rods for a long period of time, you should also paint them with shellac, nail poilish or Minwax and create a barrier ...
ttyle
Eric
O/ST