Cast Iron butterfly valves (4"-84") on a SS316L piping. In order to avoid galvanic corrosion I have specified all valves to be rubber lined on interior surfaces and flange faces with Neoprene to a thickness of 1/8".
Butterfly valves typically use a rubber liner as the seat and stem seal.  The liner extends around the face of the body and acts as the line gasket also.  If you are planning to take an existing metal butterfly valve and add a third-party coating, the coating will probably interfere with the movement of the vane in positions near closed. 
Third-party linings are usually bonded.  Manufactured Lined butterfly valves usually have liners that are replaceable. The valve liners are regular consumable service items. 
Frequently I see stainless valves used in rubber-lined pipe.  This is the first time I have seen someone wanting to rubber line valves in stainless pipe. 

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