Yes, we have the same issue. Our are gasketed with Frenzelit Isoplan 500, which is made of “biosoluble mineral fiber” per the Frenzelit website. We’ve painted the exposed portions when replacing the rupture disc assemblies and made up home-made rain covers for the flanges to keep the rain off, hoping to extend the life of the gaskets.
In my opinion, this is the wrong material for outdoor applications, especially here in Florida on peaking units that are offline most of the time