A pressure transmitter connectable to a process line provides an output responsive to a pressure in the process line. The transmitter includes a housing having a base with a process end coupled to an interior cavity formed in the housing, a sensor for sensing the pressure and an isolating assembly mounted at the process end of the housing and isolating fluid in the process line from the interior cavity. The isolating assembly includes an isolation diaphragm configured to be fluidically coupled to the process pressure in the process line, and an isolator plug positioned in the process of the housing adapter. The isolator plug having a lower plug portion providing a first end surface adjacent the isolation diaphragm, an upper plug portion providing a second end surface distally spaced from the first end surface and adjacent a sensor cavity in which the sensor is positioned, a connection mechanism connecting the lower and upper plug portions, and a capillary filled with isolation fluid and extending from the first end surface through the lower and upper plug portions to the second end surface thereby coupling the pressure through the isolation diaphragm and the capillary to the sensor cavity and the sensor. The upper plug portion is formed from a first material and the lower plug portion is formed from a second material having higher corrosion resistance than the first material.