I'll tell you one that seems to corrode a 'steel pretty fast- the outgassing/vapors from Weber BBQ grill lighters. Those little cubes seem to be the same thing as WetFire tinder but in bulk and much cheaper. I Filled a small Plano flip top tackle box with the Weber cubes with a firesteel and striker in the last compartment and sealed it up. The chemicals in the Weber cubes caused the Plano to warp to the point that the lid popped off and caused major corrosion to the steel and striker, all in the period of a couple weeks! I repeated the experiment with an identical box, making sure there was no moisture, just to verify it was the cubes, and I got the same result. This tells me some chemical or gas is being emitted from them that's strongly corrosive. Heck, maybe it's simply water coming out but nothing seems damp. I think it's probably best to keep the cubes sealed seperately from the steel. FWIW the cubes still worked just fine.