You seem to be worried about water eroding away resin or something to that effect. The bonds are strong enough that’s basically not a concern. It’s kinda like being worried about a Teflon storage medium because it’s got a bad safety sheet.

My recommendation is find something that’s waterproof on curing that can handle both ends of the pH spectrum and call it a day. You aren’t worried about abrasives.

Edit: UV too, depending on where it will be could be a concern, but petg isn’t UV ready either.