A method of sensing corrosion of a pipe covered by a layer of insulation comprises positioning a CUI sensor radially adjacent an outer surface of the pipe. The CUI sensor comprises a non-conductive base having a first end and a second end opposite the first end. In addition, the CUI sensor comprises a first test circuit mounted to the base. The first test circuit includes a first conductor, a second conductor, and a first testing element extending between the first conductor and the second conductor. Further, the method comprises exposing the first testing element to the same environment as the outer surface of the pipe. Still further, the method comprises determining whether the first testing element has corroded through. Moreover, the method comprises assessing whether corrosion of the pipe has occurred based on the determination of whether the first testing element has corroded through.