Piezoelectric transducers have been extensively used in various applications in recent decades, such as in the non-destructive testing (NDT) of materials and structures. A piezoelectric transducer commonly used in NDT applications is lead zirconate titanate (PZT) ceramic, which is thin, lightweight, and minimally invasive to the structure. In this study, we analyzed the use of commercial piezoelectric diaphragms for damage detection based on the electromechanical impedance (EMI) method, which is an NDT technique used in structural health monitoring (SHM) applications. The commercial diaphragms have the advantages of being low cost and readily available. To assess their feasibility for damage detection, a low-cost diaphragm was compared with a conventional PZT ceramic with similar shape and dimensions. Tests were performed on aluminum beams, in which damage was simulated by placing a metallic bolt at different distances from the transducers. The sensitivity to damage was estimated using the correlation coefficient deviation (CCD) damage index, which was calculated using the electrical impedance signatures obtained from each transducer. The experimental results indicate that the piezoelectric diaphragms are able to detect damage; therefore, this study provides an important contribution to the field of SHM systems based on the EMI method.