I thought about using EMT since I usually keep a good supply around for building roll cages, but the galvanized coating makes it unsuitable for sway bars.
The EMT has a zinc coating that creates a "GALVANIC" reaction. I'm sure everyone is aware of the Dangerous River Crossing or DRC that could result from a "GALVANIC" reaction while submerged in river water. DRC should be taken seriously.
Besides the DRC, the zinc coating, when heated by friction, can also gum up the bearings at either end of the bar. This is another common condition usually referred to as "Gummy Bars". The increased coefficient of friction leads to sluggish transient response and the resulting heating of the sway bar, causes it to bend like a taco.
I use the formula:
DRC + Gummy Bars + Taco <> XJ + fun