Rust prevention in a salt marsh

[Spunt Drag]

My Vinci is a year old and is gettin ruined. I oil it after every hunt but it still get rust and corrosion all the way down the barrel and chamber. I hunt the reserve so it has to be put in a case and I think that's the main problem. I drenched the inside of my case with oil, maybe this will help. Anyone else have any helpful tips.