A feedthrough assembly, which comprises: a) an insulator of electrically non-conductive material having a height defined by an insulator sidewall extending to a first insulator end and a second insulator end, wherein the insulator has at least one terminal pin bore extending from the first end to the second end thereof; b) a terminal pin received in the terminal pin bore, the terminal pin having a sidewall extending to opposed first and second ends disposed spaced from the respective first and second insulator ends (26, 28); and c) a ferrule of an electrically conductive material and comprising a ferrule opening defined by a surrounding sidewall extending to a first ferrule end and a second ferrule end, wherein the insulator is supported in the ferrule opening, characterized by d) the terminal pin comprising a terminal pin core of a first electrically conductive material and an external outer coating of a second electrically conductive material selectively applied to and directly supported on discrete portions of the terminal pin core, wherein one discrete portion lies within a terminal pin proximal end portion, positioned between the first insulator end and the first terminal pin end, or within a terminal pin distal end portion, positioned between the second insulator end and the second end of the terminal pin, wherein the external outer coating comprises multiple compositions for multiple discrete portions, respectively; and e) a first braze material contacting the coating of the second electrically conductive material on the terminal pin core thereby hermetically sealing the terminal pin to the insulator and a second braze material hermetically sealing the insulator to the ferrule. a) an insulator of electrically non-conductive material having a height defined by an insulator sidewall extending to a first insulator end and a second insulator end, wherein the insulator has at least one terminal pin bore extending from the first end to the second end thereof; b) a terminal pin received in the terminal pin bore, the terminal pin having a sidewall extending to opposed first and second ends disposed spaced from the respective first and second insulator ends (26, 28); and c) a ferrule of an electrically conductive material and comprising a ferrule opening defined by a surrounding sidewall extending to a first ferrule end and a second ferrule end, wherein the insulator is supported in the ferrule opening, characterized by d) the terminal pin comprising a terminal pin core of a first electrically conductive material and an external outer coating of a second electrically conductive material selectively applied to and directly supported on discrete portions of the terminal pin core, wherein one discrete portion lies within a terminal pin proximal end portion, positioned between the first insulator end and the first terminal pin end, or within a terminal pin distal end portion, positioned between the second insulator end and the second end of the terminal pin, wherein the external outer coating comprises multiple compositions for multiple discrete portions, respectively; and e) a first braze material contacting the coating of the second electrically conductive material on the terminal pin core thereby hermetically sealing the terminal pin to the insulator and a second braze material hermetically sealing the insulator to the ferrule.