Silicone over the stud/nut is not wise

We (local access society on Vancouver Island) are rehabbing an old crag, and found many bolts slathered with silicone. This route was put up in 2002 (didn’t we collectively know better by then?). This particular hanger came off with a slight tug, and after peeling back the silicone, the nut was completely gone, although a hexagonal void was left behind in the silicone where it had been.  If there had been a washer, it was corroded to nothing as well. The stud and hanger are in excellent shape.  I can only assume plain steel nuts were used, and the silicone was a misguided attempt to protect it.   We are now in the process of removing every hanger with a similar silicone “treatment” and replacing with new bolt and hanger. 

Yes, people should know better and thank you!

The case of the disappearing nut! That’s pretty wild to see. I’ve pulled some silicone covered bolts here in the arid desert placed many moons ago, we don’t have the same moisture issues and the nut has always been there. Not condoning it, just mentioning.

Many one-part silicone caulks release acetic acid which can be immensely corrosive to all kinds of metals.  That's that sour curing smell you might notice when you apply it.  Two-part silicone, or "Electronic Grade" one part silicone doesn't do this, although trying to apply a sealant to protect mild steel in a temperate rainforest like Vancouver Island is a pointless endeavor.