Media-resistant multi-layer coating for a measuring device of process

Field device (7, 12) for the process and / or automation technology for monitoring at least one chemical or physical process variable of a medium (16) in an at least partially and temporarily fluid-carrying component (17) comprising at least one electronic unit (14) and a sensor unit (15 ), wherein at least one component (3) of the sensor unit is at least in a partial region and at least temporarily in contact with fluid, wherein at least the wetted portion of the component (3) having a media-resistant multi-layer coating (2) two layers is provided from at least a first layer ( 4) consists of a material which is composed of a closely packed array of atoms, and which causes a corrosion protection for the medium, wherein the first layer (4) a second layer (5) is arranged, which consists of a chemically resistant plastic, and which has a protective layer of the first un against external damage d corrosion offers.