The switch is purposely not placed close to the bottom of the pillar. The pillar itself is about 2 meters high, and the switch is located in the upper area. There is other electronics build into the pillar, which does not show issues. Also, of the two active network connections, only one uses PoE, and that one shows the corrosion.
That mikrotik switch (actually it's a router) looks nice, they also have a version with SFP uplink, which I would need. But to be honest, that case does not really look moisture proof to me.
But if it is time to replace the switch, I will take that into consideration.
Actually, scratch that, that thing does not support proper 802.3af PoE.
Using specialized and expensive harsh condition equipment is the last option.