Zircaloy-4, one of zirconium alloys, has outstanding corrosion resistance to nitric acid. Utilizing potentiodynamic polarization, ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS), and Mott– Schottky analyses, the ELECTROCHEMICAL behavior of zircaloy-4 in nitric acid solutions were evaluated under open circuit potential (OCP) condition. At first, where the concentration of nitric acid increased from 0. 01 to 0. 05 M, the corrosion current density decreased. However, it amplified rapidly while the concentration increased from 0. 05 to 0. 50 M. Moreover, the EIS studies demonstrated an inverse trend for polarization resistance values. Mott– Schottky analysis indicated that the passive films displayed p-type semiconductive characteristics. Also, this analysis showed that the acceptor densities decreases by increasing nitric acid concentration from 0. 01 to 0. 05 M, whereas it increases when the nitric acid concentration reaches from 0. 05 to 0. 50 M. This trend was consistent resulting in potentiodynamic polarization and EIS measurements.

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) is a powerful method for investigating various ELECTROCHEMICAL systems. The technic involves application of a small amplitude alternative current (AC) perturbation to the ELECTROCHEMICAL system and recording its response, and therefore it is considered a non-destructive monitoring technic. This article describes the scientific fundamentals for the EIS method, instrumentation of the method, especially different electrode configurations (2 or 3 electrode systems and comb-shaped or interdigitated electrodes), and also various fields where corrosion monitoring and analysis has been carried out by EIS. These include: atmospheric corrosion, concrete corrosion, analysis of performance of surface films and coatings, study of inhibitors, high temperature corrosion and oxidation, corrosion in gas and oil industries, microbiologically influenced corrosion (MIC) and stress corrosion cracking (SCC). The most recently published literature has been surveyed and typical equivalent circuit models, capabilities of the EIS technic and limitations of the technic are highlighted for each application. This article is a free translation and re-composition of two chapters about IES from references [1] and [2].

The effect of the thickness of ceramic membrane on the productivity of microbial fuel cells (MFCs) was investigated with respect to the electricity generation and domestic wastewater treatment efficiencies. The thickest ceramic membrane (9 mm) gained the highest coulombic efficiency (27. 58± 4. 2 %), voltage (681. 15± 33. 1 mV), and current and power densities (447. 11± 21. 37 mA/m2, 63. 82± 10. 42 mW/m2) compared to the 6-and 3-mm thick separators. The results of ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) analysis were investigated to identify the internal resistance constituents by proposing the appropriate equivalent electrical circuit. The Gerischer element was modeled as the coupled reaction, and diffusion in the porous carbon electrodes and the constant phase element was assimilated into the electrical double-layer capacitance. The thickest ceramic (9 mm) was found to have the largest ohmic resistance; however, owing to its superior barrier capability, it provided more anoxic conditions for better accommodation of exoelectrogenic bacteria in the anode chamber. Therefore, lower charge transfer, fewer diffusional IMPEDANCEs, and higher rates of anodic reactions were achieved. Excessive oxygen and substrate crossover through the thinner ceramics (of 6 and 3 mm) resulted in the suppressed development of anaerobic anodic biofilm and the accomplishment of aerobic substrate respiration without electricity generation.

In this research, UNS S42000 martensitic stainless steel (SS) samples were subjected to tempering heat treatment at constant temperature of 550 oC for different time duration, ranging between 0. 5 and 24 h, so as to assess the intergranular corrosion (IGC) behavior of the alloy. The microstructural characteristics and ELECTROCHEMICAL properties of the alloys were evaluated using scanning electron microscopy (SEM) and anodic polarization method, respectively. The localized attack of the samples was investigated by potentiodynamic ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (PD-EIS) in the transpassive potential region. The results indicated that tempering up to 2 h would be followed by severe intergranular attack at martensite lath interfaces; however, the effect of tempering on corrosion performance of the alloys would be suppressed at prolonged tempering due to desensitization. Moreover, the PD-EIS results revealed that the charge transfer resistance (Rct) values of specimens at 1. 10 V can be employed as a primary criterion in order to assess the localized attack of the martensitic SS. In this regard, the lower the Rct value at this DC bias potential, the lower the corrosion resistance to the IGC. These results were in good agreement with the SEM morphologies from the surfaces of corroded samples, indicating uniform corrosion, severe attack and desensitization for samples experiencing no-tempering, short tempering time and prolonged tempering, respectively.