A corona igniter including a hermetic combustion seal between an insulator and center electrode is provided. The combustion seal includes a metallic coating, such as a nickel-based layer applied to a layer of molybdenum-manganese, and the metallic coating is disposed on the insulator inner surface. Optionally, a shot of copper-based powder can be disposed on a head of the center electrode. The center electrode and/or the copper-based powder is then brazed to the metallic coating on the inner surface of the insulator. The process can include applying the metallic coating to the inner surface while applying a metal coating to an outer surface of the insulator. The method further includes brazing the center electrode and/or the copper-based powder to the metallic coating on the inner surface while brazing the metal coating on the outer surface to a metal shell.