As an e.engineer, I would NOT put salt at electronic circuits, and prefiribly water neither - vinegar is mainly water. Chlorides ions are badly corrosive to metals, while sodium ions are deadly for semiconductors, and for instance plastic packages don't stop sodium ions. Additionally, even the slightest trace of salt on a printed circuit botches the insulation resistance.
If salt water came in contact with an electronic circuit, you should rinse with plenty of tap water, then with destilled water, then with absolute alcohol to remove the water.
Copper will not stay clean in the normal atmosphere. Traces of chlorine ions accelerate its corrosion. The proper way to keep a clean surface is to cover copper with a better alloy, for instance with solder, tin, nickel, palladium, gold...
Slightly tarnished copper can still be soldered. That's the role of the rosin flux in the solder wire. Satellite manufacturers have got it wrongly, and instead of rinsing the flux after soldering, they use solder wire without flux, hence have difficulties at soldering, and bad contacts. Too bad for them.
If the shape of the copper parts to be cleaned permits it, by far the best cleaning method is mechanical. Take the rubbing side of a sponge, rub a bit, done. On flat surfaces, even an eraser can give good results.