A corona ionization source assembly and fabrication methods are described that include a fine wire including a wire core including a first material, and a wire coating including a second material, where the wire coating surrounds a portion of the wire core, and the diameter of the wire coating is greater than the diameter of the wire core. Additionally, the fine wire may be coupled to a mounting post. In an implementation, a process for fabricating the corona ionization source assembly that employs the techniques of the present disclosure includes forming a wire core, forming a wire coating that surrounds the wire core, forming a mask layer on at least a portion of the wire coating, etching the wire coating, and removing the mask layer from the wire coating.