But if you have one, carry a didcated striker, or even better, a nice, short, high carbon steel bastard file. It will get the flakes off, and it will strike. After that, a bit of cheapo hacksaw blade.
The file on my Wave makes quick work of getting nice filings. And you can use the edge to strick parks. In fact, almost any sharp edge can be used. I've generated sparks with small rocks and broken pieces of glass.
BTW, regarding white corrosion due to humidity. Apply a coating of clear nail polish on the mag bar to prevent contact with the air. The coating scraps off easily when the bar is needed.