A frequency sweep from 50 to 200 kHz of guided mechanical waves have been conducted to detect and assess corrosion damage in steel reinforced mortar specimens with seeded defects and in specimens undergoing accelerated corrosion using impressed current. The sweep was conducted by invoking primarily the fundamental longitudinal mode of propagation, i.e., the L(0,1) mode. The decay of waveform energy (indicative of attenuation) at different frequencies is presented and discussed in terms of corrosion damage. Experimental results indicate that the percentage of corrosion damage can be detected and evaluated invoking the fundamental longitudinal mode of propagation.