Impossible in my opinion. Any coating can scratch or chip if abused. And keep in mind that any coating may protect the metal to a degree, but it still can still corrode underneath the coating. And you can't really efficiently coat the internals of the gun, but you can make them out of stainless
. Especially the inside of the barrel. Coating a barrel and action may protect the outside of it, but it won't do much for the inside.
The only way you can remove cerrakote is via bead blasting and no the finish won't corrode underneath. Ultra bore coat is all about making the inside of a barrel easier to clean and less likely to foul and as a side benefit not likely to corrode. FWIW Stainless by itself will corrode and sometimes badly.If your going to rely on all stainless with no coating better buy a weatherby SS gun either a vanguard or Mk because they are the only ones made of 410 which is stronger and less likely to corrode then 416.