I cannot remember the correct term for this. Corrosion of the copper will generate copper sulphate (and other salts) which conduct electricity.
It may be worth spraying with something to prevent it reforming, e.g. 'conformal coating' or even WD40, but keep the spray to the area only as some relays do not like silicone. Many years ago, I heard of a telephone exchange getting a sudden increase in relay contact failures when the cleaners went from using bees-wax to silicone floor polish!
Radio Control modellers see something similar: it's called 'Blue Death' (or is it Green Death?, can't remember), in which the cable from a NiCd battery pack to the receiver corrodes.
Last edited by AlisterW; 25/09/21 01:00 PM. Reason: Extra information added.