BACKGROUND/AIMS: This study’s goal was to assess and make a comparison of the electrochemical corrosion rates of nickel-titanium (Ni-Ti) rotary files in cases of their immersion in four various irrigation solutions. Another goal of this research was to investigate and compare the areas of corrosion on the file surface under a scanning electron microscope (SEM). MATERIALS AND METHODS: The Tafel extrapolation method was employed to perform the electrochemical determination of the corrosion rates of twenty-nine ProTaper Universal Ni-Ti rotary files in 2.5% sodium hypochlorite (NaOCl), 5% NaOCl, 15% ethylenediaminetetraacetic acid (EDTA) and 2% chlorhexidine gluconate (CHX) irrigation solutions (7 files were tested for each irrigant). Data were acquired by utilizing a combined system which contained a voltage scan generator, a potentiostat, and a recorder. In order to find corrosion rates, an extrapolation to corrosion potentials of the linear region of anodic currents acquired from electrochemical current-potential curves was performed. The Kruskal-Wallis One-Way analysis of variance was performed to analyze the data statistically. One randomly selected file from each test group was examined under SEM. RESULTS: The corrosion rates of Ni-Ti rotary files in the examined solutions under SEM from the maximum to the minimum were as follows: 5% NaOCl >15% EDTA >2.5% NaOCl >2% CHX. CONCLUSION: The findings of the present research demonstrated that 5% NaOCl, 15% EDTA, and 2.5% NaOCl led to significant corrosion on the surface of the chosen Ni-Ti rotary files.