Henry,
excellent! As always...
I am honest, as I have read Tommy's post the first time I had similar thoughts on this.
But nevertheless, I yet like the basic question: "...a little co2 from some dry ice+water in a bucket and hosed in to the tube is not a bad second option eh?"
This once is a very... hmmm... trying to find the right term... 'unconventional'(?) approach to an existing task. I truly like it - certainly also as I personally have never thought about using CO2 for purging operations.
And honestly spoken as well. From my humble point of view Henry, you should be absolutely right by considering the Carbon dioxide dissociation. But... as well-known a specific amount of energy is needed to separate the first of the two oxygen atoms from the CO2 molecule, or:
CO2 + 1184,87 kJ --> CO + O
As I mean to know, these reactions are taking place, e.g. with GMAW within the arc's "hot" core (please forgive me the casual formulation) as the first of generally two reactions. Here the dissociation of CO to C + O is furthermore another topic as it reqiures more energy than the first one, what's the reason for that the dissociation of Carbon monoxide is in most cases just partial.
So, when considering the GTAW arc as being in direct contact with the CO2, coming from Tommy's dry ice, then I would mean yes, there is a partial dissociation of CO2 - eventually to CO + O. The oxygen again would - as described so excellently by you - lead to oxidation or sugaring etc.
But my question(s) in general would be: "What would happen as the CO2 is not in direct contact with the arc (surely this wouldn't work as far as the root is welded on an open gap)? Would the energy - just based on 'heating up' the rear side - suffice to dissociate the CO2 molecule? And if (most likely) so, how would the rear side really look like?"
I was glad to read Tommy's final comment: (quote): "... Now I want to try it just for the heck of it to see what happens..."
That's great! Please keep us informed on the outcome, Tommy!
All the best,
Stephan