Abstract: The non-invasive corrosion sensor includes a heat sink, at least two peltiers, a reference standard and a data acquisition device. Each peltier has a negative side and a positive side, and each peltier communicates with the heat sink such that the negative side of each peltier is maintained at a common temperature. The reference standard communicates with the positive side of one of the peltiers while the test piece communicates with the positive side of the other peltier; and the data acquisition devise is able to record and compare the differences in temperatures between the test piece and the reference standard. A higher temperature in the test piece than in the reference standard indicates the presence of corrosion. The differences in temperatures of the test piece and the reference standard are obtained via electrical currents in the peltiers.