Navy magnesium-carbon diving composite (Panama City)

Two applications of the same magnesium-carbon composite: salvage (generates hydrogen on contact with seawater, lifts objects via plastic-bag flotation) and diver thermal protection (corrosion heat warms diver in cold water). Demonstrates "magnesium corrodes really well" point.

The Navy loves it. Panama City is where Navy divers do things, and they have a little research lab. A number of years ago they developed a magnesium-carbon composite. They take carbon powders and magnesium powders and press them together, and you can stick this in seawater. If you try to polish it in the laboratory and you use a water-based polish slurry, it would corrode faster than the new propulsion — so they use oil-based polishing. But if you stick it in seawater, one use they found was salvage. You put it in a little plastic bag. The diver takes it down beneath the surface, gets a big plastic part, puts it over whatever he wants to lift, connects it, puts the little plastic-coated piece of magnesium-carbon alloy underneath, breaks the bag, seawater comes in, and he generates a hydrogen bubble that floats the thing to the surface. That's how fast it corrodes — you can generate your own hydrogen underwater. So you don't have to carry big tanks of gas that are lighter than water; you can carry a little thing and the water will produce your own gas.