Yes its inert as far as I am aware. But you will find epoxy more difficult to mix so experiment first. Also be aware that epoxy is not a very good gap filler and does tend to crack if the mass effect is great.
Thanks for that info, I am intending to thicken up some epoxy resin to fair in after I’ve used it to attach my new transoms. I’ve been told that polyester filler will not adhere well enough to the epoxy join. All academic until I can get 24hrs of mild dry weather.
If it's an epoxy glue you are looking for, I would use Micro Fibres, very strong and easy to build fillets with, just make sure you clean up any excess.