I did my due diligence and saw no other posting on this. So here goes.......
I recently ran out of tig rods and have around 10 lbs of gas welding rods. So I had a little project out of steel that needed some filler rod so I did a little test.
Here is what I found. Do not use gas welding rods for tig. You will get porous welds with lots of pits and a very weak weld. I did a little research on this and found that tig rods have higher concentration of silicon and other de-oxidizers that are more suited for tig welding.
I also tried the old standby for gas welding...the coat hanger. I suggest not using coat hangers any more even for gas welding. For tig, coat hangers should never be used as the metal they are made out of are probably your old Toyota with lots of crap in them. I tried one and I was amazed how bad the weld was. Like bird poop blobs everywhere.
I then, just for the fun of it, decided to try mig wire. Specifically ER70S .30 wire. I tried a single strand and found controlling the flimsy wire was tough. So I took the wire, doubled it over and twisted it together with a cordless drill in effect doubling its diameter and making it fairly stiff. That seemed to work. The welding with that was smoother with no porosity at all.
So in a pinch, if you really need to tig weld something say on a Saturday, are out of rods, the LWS is closed and have some mig wire laying around, it may be the answer.