This paper presents the corrosion degree effect on yield and ultimate strengths (nominal and effective) of protruding reinforcing steel that remained buried for 60 years; thus, the natural corrosion process during this period was analyzed. Tensile tests were performed on specimens taken from this protruding reinforcing steel. A characterization of the local soil where the reinforcement remained buried as an aggressive medium was performed, and micrographs were obtained in order to observe the presence of pits. The results were in agreement with studies of accelerated corrosion in a laboratory. As the corrosion degree increases, the greater is the difference between the nominal and effective strengths. Specimens with a corrosion degree of about 25% had an effective strength similar to specimens with lower corrosion degrees. Thus, care must be taken in interpreting the effective strengths for predicting the capabilities of structural elements degraded by corrosion.