I have an NXT that had AA batteries (alkaline, I think) in it for a long time and they leaked battery acid.
I took the batteries out when I became aware of the problem, and have cleaned off the terminals, and popped the cover off the NXT to have a look at it. I'm hoping the unit is fine -- I can't readily tell without further disassembly -- but was wondering what recommendations you might have for how to proceed. I have not attempted to power up that NXT since removing the batteries.
I don't know how far apart you are comfortable taking it, but I would take it apart almost entirely (de-solder the PCB from the battery terminals). I usually use rubbing alcohol and a tooth-brush [Edit: an old tooth-brush, to be thrown away afterwards] to clean things up. If the acid didn't get to the PCB, then after cleaning the contacts, you should be good to go.
yes, rubbing with vinegar is a good choice because alkaline batteries don't have acid like lead-acid batteries in cars but.... alkali !
This is just the opposite.
Vinegar is an acid (5% acetic acid) and neutralizes the battery's alkali.
Alternatively, you may use highly diluted tartaric acid or ascorbic acid, both are also complexing metal ions, and moreover, ascorbic acid ("vitamine C") is also a redox agent against oxidative or reductive matters, like, e.g., Mangan oxide in alkaline batteries.
Cleaning with 50-70% alcohol afterwards will probably remove the rest of the corrosion (and excess of acid ions).