My two cents,
The fact that it is non-flammable is not enough to classify it as non-DG. ALL prescriptions of the DGR must be respected!
If it contains mercury, it must respect the relevant procedure for it.
The packaging used must be suitable for air transport even if it is non-DG (vibration, pressurization,..) . If it is DG, the packaging must respond to even stringer rules.
Otherwise, what about a huge tank of 15.000 liters of water,....
It is non-flammable, but if it leaks, I think corrosion will be a real minor factor compared with trim problem