A hermetically sealed filtered feedthrough assembly for an active implantable medical device includes an electrically conductive ferrule hermetically sealed by a first braze to an insulator. A conductor is hermetically sealed to and disposed through the insulator. A filter capacitor has an active electrode plate and a ground electrode plate which are disposed within and supported by a capacitor dielectric in an interleaved, partially overlapping relationship. A first passageway is disposed through the capacitor dielectric having a capacitor internal metallization which is connected to the active electrode plate. A capacitor external metallization electrically connects to the ground electrode plate. An oxide-resistant metal addition includes a conductive core with a conductive cladding of a different material. A first electrical connection is between the oxide-resistant metal addition and the capacitor external metallization. A second electrical connection is between the oxide-resistant metal addition and the ferrule.