An electromagnetic sensor was assessed as a possible instrument for nondestructive detection and monitoring of corrosion in structural carbon steels. In this study, the magnetic response of three structural carbon steel rods (AISI 1018, AISI 1045, and AISI 1045-High Mn), was evaluated in the as-received (uncorroded) and corroded conditions. Initially, the material was systematically machined out from each steel rod, followed by the magnetic evaluation of each specimen. Other set of metal rods were exposed to uniform corrosion and later examined by the electromagnetic sensor. Correlations have been established between the degree of mass loss and magnetic response of the test specimen. Based on the results, it can be said that the electromagnetic sensor has the potential to be used as a reliable nondestructive tool to detect corrosion at early stages based on the variation in magnetic properties. A metallurgical analysis of all test rods was also undertaken, which showed that microstructures have an important effect of the magnetic properties of the steels. Copyright © 2008 by ASME.