lined, or plated? All the cylinders I've seen have been chromium plated rather than mechanically lined.
I'd be careful with caustic soda since it's very aggresive and if the liner plating is compromised, I suspect it could undercut the plating quite easily.
Incidentally, another strong etchant for aluminium is a mixture of salt and copper sulphate, I use this for deep etching in aluminium and it's very fast. Suggest you keep treatment very local to the galled area; ie the bit you actually want to work on. My suggestion - haven't tried this but it should work, your risk etc - would be to paint the inside and base of the cylinder with tar paint, leaving only the bit you want to work on, make a little well around it with plasticene or similar, spoon etchant in and pour it out. Tar paint is resistant to most water-based corrosives, being highly hydrophobic. Remove afterwards with thinner or petrol.
BMW had trouble with Nikasil liners a while back, all the 4.0 litre V8s in Britain started developing poor compression and low power as the sulphur in the fuel corroded the liners. they replaced thousands of engines under warranty before switching to Alusil.