Frequency Responses of Molar Electrochemical Peltier Heat and Entropy Changes Analyzed as Thermometric Transfer Functions

This work proposes a theoretical framework to obtain the frequency response of molar electrochemical Peltier heat and entropy changes induced by a modulated electrical signal. This is based on an internal energy balance developed for a working electrode thermistor in ac regime. Then, from an analysis that correlates the electrochemical impedance and the interfacial temperature variation, two new transfer functions that depend on the frequency ω, named as entropy changes ∆S(ω), and molar electrochemical Peltier heat, Π(ω) are obtained. This strategy is tested in two electrochemical systems: the ferrocyanide/ferricyanide couple and the copper ions in an acid sulphate-chloride medium. Both systems are analyzed by dc thermometric measurements, electrochemical impedance spectroscopy and ac-thermometric experiments namely variation of interfacial temperature. As a result, ∆S(ω) and Π(ω), are obtained and their values are correlated to the relaxation processes involved in the electrochemical reaction. Additionally, a brief discussion is included concerning the differences between the classical dc thermoelectrochemical methodology and the proposed approach here.

Inhibitive Characteristics of Cefalexin Drug Addition on Corrosion Evolution of Mild Steel in Chloride Medium

The inhibition effect of Cefalexin on the corrosion of mild steel in sodium chloride has been examined with the use of weight loss and potentiodynamic polarization methods at ambient temperature. Cefalexin showed good protection ability by adsorbing on the mild steel surface. The mixed inhibition characteristics of Cefalexin were revealed by the Potentiodynamic polarization results. The inhibitor efficiency was found to be above 65% obeying the Langmuir and Freundlich isotherm law with correlation regression coefficients of R2 = 0.9984 and R2 = 0.9488, respectively. The closeness of these R2 values to unity established the reliability of Cefalexin as an inhibitor.