Rust-Away and Rubies

Never mind Rustoleum. I have a new product that turns pure rust (iron(iii) oxide, or the mineral hematite) into pure elemental iron almost instantly. As a bonus it creates rubies and sapphires. The main problem? It melts and welds itself to other metals.

Yes, I am finally messing with thermite, using Aluminum powder for fuel. Aluminum is what the most powerful motor ever made, the Space Shuttle Solid Rocket Booster (SRB), uses for fuel. We are in the big leagues now. 

Actually thermite is a famously exothermic reaction, creating temperatures up to 2500C. That is hot.  Twice the heat needed to melt iron. The reaction is:

Fe2O3 + 2Al -> 2Fe + Al2O3

The product aluminum oxide is the mineral corundum, which is known to us as rubies and sapphires. But we won't get any gems, just some white powder. We will also notice the pure iron that is left behind, a little more than 2/3rds the weight of the iron oxide used. This is visible as little balls of metal surrounded by the aluminum oxide. Ignore the big aluminum melt that was just the container for the reaction.

Stoiciometrically, the ratio of iron oxide powder to aluminum powder is almost exactly 3:1 by weight, and that is what is generally used. I wanted a small test so I did not blow myself up, and went with 1.5g of iron oxide and 0.5g of aluminum. 

Beside the potential to melt your spacecraft instantly, thermite is not used as a rocket propellant for a fairly obvious reason. Its reactants are solid. There is no gas released as thrust to push the rocket along. It would basically ignite, and then melt the entire spacecraft on the pad and anything in the vicinity. Not good.

So we see why rocket candy is good with its carbon dioxide, nitrogen, and water vapor gasses released. Propulsion forward is when gaseous product of a reaction inside the tank is directed to the atmosphere behind the rocket through a nozzle.

But thermite is extremely useful for things like welding railroad tracks together, underwater welding, and melting holes in stainless steel. You know, common everyday household things like that.

I should note that other metal oxides can be used with aluminum to create molten copper, etc. In this post, we are assuming iron, specifically iron(iii) oxide and not magnetite (the mineral F3O4 with iron(ii) and iron(iii) cations).