Quote:
Originally Posted by out2kayak
Normally you'd use an inert gas for shielding from atmospheric gases (such as oxygen, nitrogen, etc.) and last I checked water was made of hydrogen and oxygen in a polar covalent bond. When water comes into contact with iron it will dissociate and the oxygen will bond with the iron forming FeO2 or rust.
|
Chemically speaking, the formation of rust (Fe2O3) from elemental iron, is a process known as oxidation, although oxidation does not always include oxygen (another subject entirely, especially when discussing other metals besides iron). While it is easy to think about oxygen and water causing oxidation at ambient temperature / pressure / atmospheric content, that isn't what is going on when welding occurs, and plasma reactions are even more unusual. Plasma reactions occur in an "activated energy state" and different chemistry occurs.
The chemistry of oxy-acetylene, arc, MIG and TIG welding are probably explained well elsewhere, however corrosion at the site of the weld or cut is common, and I'd suspect that this process produces that same level of post weld corrosion or rust.
Plasma is the 4th phase or state of matter (gas, liquid, solid, plasma are the four phases of matter) and each phase has its own chemistry, especially when one phase acts on another. Plasma is a hyper-excited state of matter where so much energy is present that the electrons of the atoms are partially stripped off (i.e. some of the electrons are stripped off, not all of the electrons), notice the 14,000 degrees F in the link describing the reaction. So this new cutter or torch with water / alcohol as the working material that creates the plasma arc will not act like ambient water or alcohol when it is in the plasma phase, and the heat of the reaction will likely evaporate any residual. I'm guessing that the alcohol is present with the water to create a source of carbon and extra oxygen in the weld puddle, but that's a guess on my part.