More chemistry than metallurgy

[tripleZ]

Here's a question for those folks who deal with chemistry on a daily basis. I personally haven't dealt with it since my first year of college, so I'm a bit rusty.

I'm currently making a solution of magnesium hydroxide and isopropyl alcohol. The concentration of Mg(OH)2 in solution is about 0.2 g/cc. I'm coating parts with this, then putting them in a high heat furnace (2500+°F) under atmosphere.

Looking at the chemical formualas, I figure the magnesium hydroxide will reduce to MgO + H2O, with water vapor going up the stack and the MgO remaining on the parts. Isopropyl alcohol (C3H8O) is more of a question. If the water pulls out of that one, I'm left with C3H6 + H20, again with the water vapor going up the stack. Now, the C3H6 would be cyclopropane, a flammable gas and old school anisthetic. If this is the case, I'm guessing it would be an almost instantaneous ignition when it hit air, but because of the small quantity of it on the parts, the flame would also be short-lived. Right or wrong?

 

[kclim]

What is the purpose of the coating?

In any case, I think you're on the right track. You'd be left with MgO, with the alcohol volatilising and burning, although you wouldn't expect to see much of a flame.

If the amount of air intake into the furnace is restricted, it's possible you might see some charring (carbon).

It might be possible for the alcohol to reduce the MgO to Mg metal, but I think this only would occur at very high temperatures (2000 C), and the Mg metal would quickly oxidize to MgO once in a normal atmosphere.

 

[tripleZ]

The purpose of the coating is to keep parts from sticking together. I've seen it used in heat treating applications before, but never at this high of a temp.

I ended up running the test last night and it worked extremely well. No problems with the furnace, and the layer of MgO left on the parts with the alcohol solution actually brushes off by hand. In a water solution it seems to embed more into the parts.

Thanks for the input.