How can I remove a rusted faucet nut?

Trying to remove my Kitchen Faucet. It's around 10 years old.
The last set is to remove the Nut that holds a brass plate to fasten the faucet to the kitchen counter. .
The problem is, i think the nut that is hold that brass plate has corroded. The other problem is I have very little room to work with under the sink. Only like a 3-4 inch gap to try to loosen the nut.
Question from user Outdated Computer Tech at stackexchange.
Answer:
You might find a monobloc tap wrench that fits. They are designed for reaching up behind a basin.
Or a conventional box-wrench set, though I'd guess they are usually not long enough. You can use a normal 1/2" drive socket set to extend one.
If you are replacing the tap, you could use a rotary tool (e.g. Dremel) or similar to cut off the bottom part of the threaded tube to gain access to the nut at the top without interference from the connector at the bottom.
Clearly, water has been leaking through. You might just have limescale deposits that can be cleaned off with a limescale remover and perhaps with a wire brush (perhaps using a rotary tool again).
Answer from user RedGrittyBrick at stackexchange.

Trying to remove my Kitchen Faucet. It's around 10 years old.
The last set is to remove the Nut that holds a brass plate to fasten the faucet to the kitchen counter. .
The problem is, i think the nut that is hold that brass plate has corroded. The other problem is I have very little room to work with under the sink. Only like a 3-4 inch gap to try to loosen the nut.
Question from user Outdated Computer Tech at stackexchange.
Answer:
You might find a monobloc tap wrench that fits. They are designed for reaching up behind a basin.
Or a conventional box-wrench set, though I'd guess they are usually not long enough. You can use a normal 1/2" drive socket set to extend one.
If you are replacing the tap, you could use a rotary tool (e.g. Dremel) or similar to cut off the bottom part of the threaded tube to gain access to the nut at the top without interference from the connector at the bottom.
Clearly, water has been leaking through. You might just have limescale deposits that can be cleaned off with a limescale remover and perhaps with a wire brush (perhaps using a rotary tool again).
Answer from user RedGrittyBrick at stackexchange.

