Hi there DaddyCool, and welcome to ECN.
I can't say this is a problem I recall seeing before.
I've come across some fittings on very damp outside walls where the green stuff was most definitely corrosive. In fact, in one case it had eaten through the earth wire and partially destroyed the insulation and wire on the phase, enough that a little movement left the metal box energized!
I'm thinking of the cans of "Slime" that some of my school friends had in the late 1970s. Not sure what that stuff was made from.