Device for monitoring corrosion development in a process pipe (100) comprises a flexible electrically insulating first sheet (200) having an array of through apertures in a defined pattern and wrapped around the pipe (100). A second sheet (300) module (302) exhibiting numerous through apertures in a similar pattern as the first sheet (200) is provided with electrically conducting studs (400) arranged in said apertures in electrical connection with electrically conductive wires (500). The second sheet (300) is arranged to be wrapped around the first sheet (200) with the respective apertures aligned, and attached to the metal structure (100). The sheet (300) module (302) is arranged with numerous stud arrays (R), each stud array (R) having two or more studs (400) with their wiring (500) in electrical connection with a controller (600). The device enables prefabrication of a corrosion monitoring device.