If it's painted it's good but if you put screws to attach the piece, you break the seal in the whole so put a waterproof sealer or silicone in the whole before putting the screw you eliminate the water intrusionI need to triple check, but my painter did his absolute best to encapsulate it from both sides.
So, I think it's painted as best as it can be. If factory paint lasted 34 yrs, this round should do ok.
Just trying to search any other "causes" of this rot, and haven't found anything on CK5.