Linear polarization resistance and electrochemical impedance spectroscopy (EIS) are widely applied in corrosion for studying the electrode/solution interface, films, coatings, and corrosion rates. Most potentiostatic and galvanostatic EIS measurements are based on the use of a perturbation signal (i.e., frequency or amplitude modulation of a sine wave) applied to the specimen. The determination of corrosion rate via linear polarization resistance and EIS requires the constants of Tafel slopes in the cathodic and anodic reaction of a corrosion process, but these techniques cannot provide that. The present instrumentation research is related to the modulation of frequency and amplitude for development of harmonic analysis and total harmonic distortion. The main purpose of this preliminary study is to increase the signal-to-noise ratio and to obtain additional information about the corrosion system (e.g., corrosion rate, Tafel slope). Variable amplitude signals can increase the signal level for higher-quality EIS data. However, the voltage amplitude cannot follow a linear relationship when the impedance increases at lower frequencies. Even though a high-amplitude sine wave will bring distortion in the response signal when a signal with a high-amplitude sine wave is applied on the corrosion system, the corrosion rate and Tafel slope can be derived from higher harmonics of the response signal. Frequency and amplitude modulation techniques and their application to corrosion are discussed and reviewed in the present research.