Investigating the efficacy of Curcuma longa against Desulfovibrio desulfuricans influenced corrosion in low-carbon steel

The effectiveness of Curcuma longa extract in the control of low-carbon steel corrosion caused by sulfate-reducing bacteria (SRB) in Baar’s medium was investigated. The SRB taken for the study was Desulfovibrio desulfuricans. Specimens in contact with the medium containing SRB exhibited a corrosion rate more than 10 times that of the specimens in contact with the medium without SRB. The weight loss studies showed that the addition of 50 ppm C. longa extracts to the medium containing SRB resulted in an average inhibition efficiency of 91.2% for a four week immersion period. The inhibitor extract altered the reaction rates of both cathodic and anodic reactions which were confirmed from the potentiodynamic polarization (PP) studies. Electrochemical impedance spectroscopy (EIS) studies showed a reduction in the number of sessile bacteria upon inhibitor addition which was confirmed by the microscopy. Severe pitting was observed in the morphological analysis of the specimen in the absence of inhibitor treatment. Apart from adsorption onto the specimen surface to minimize the biocorrosion, the inhibitor extract also served as an anti-film forming and antibacterial agent.

Alleviation of Iron Corrosion in Chloride Solution by N,N′-bis[2-Methoxynaphthylidene]amino]oxamide as a Corrosion Inhibitor

The alleviation of iron corrosion in 3.5% NaCl sodium chloride solution using N,N′-bis[2-methoxynaphthylidene]amino]oxamide (MAO) as a corrosion inhibitor has been reported. The work was achieved using various investigation techniques. Potentiodynamic cyclic polarization (PCP) displayed a powerful inhibition for the corrosion via reducing the iron’s cathodic and anodic reactions. This was reflected in reduced corrosion currents and increased polarization resistances in the presence and upon the increase of MAO concentration. The electrochemical impedance spectroscopy results indicated that MAO molecules provoke the corrosion resistance via increasing polarization resistance. The power of MAO on decreasing pitting attack was also investigated through measuring the change of current with time at −0.475 V(Ag/AgCl). Scanning electron microscopy images were taken of the surface after the current–time measurements were performed in the absence and presence of MAO. The current-time experiments indicated that MAO highly mitigates the corrosion of iron. The energy dispersive X-ray analyzer reported the products found on the tested surfaces. The effect of extending the exposure time from 1 h to 48 h was also tested and was found to alleviate the corrosion of iron, whether MAO molecules are absent or present.

Expired Chicken Egg-White Extract’s Adsorption Behavior As a Corrosion Inhibitor for Carbon Steel in 1M HCl

The inhibitory activity of the expired egg-white carbon steel (CS) extract in HCl solution was studied in this article. The extract was examined using FT-IR, and the surface was examined using a scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDX). Weight loss techniques at various temperatures were used to examine corrosion investigations (298, 308, 318, and 328 K), concentrations (100, 200, 400, and 800 mg. L−1) of extracts, and electrochemical measurements (potentiodynamic polarization (PDP) and impedance spectroscopy (EIS) at 25°C and different concentrations. Results. Results obtained through EIS demonstrated a maximal inhibition efficiency of 90% at an inhibitor concentration of 800 mg. L−1. Moreover, the findings of the potentiodynamic polarization indicated that egg-white extract was a mixed type of inhibitor and slowed down both cathodic and anodic reactions. For weight loss analysis, an inhibitory potency (89, 83, 77, and 71%) at various temperatures (298, 308, 318, and 328 K) was demonstrated, respectively. It indicates that the temperature rise contributes to a decrease in the resistance of the carbon steel. The adsorption of the expired egg-white extract was spontaneous with physisorption and chemisorption according to the Langmuir isotherm model, according to adsorption isotherm studies.

Electrochemical mechanism of metall corrosion

Corrosion that occurs by an electrochemical mechanism is a combination of cathodic and anodic reactions that occur independently of each other. At that, the metal surface is considered to be equipotential one, i.e. the presence of short-circuited microgalvanic pairs on the surface is not a necessary condition for electrochemical corrosion. The anode and cathode processes are spatially separated. This is provided by the presence of conduction electrons in the interstitial spaces of the metal lattice. The present model of electrochemical corrosion justifies the use of polarization diagrams for the analysis of corrosion processes. The previously proposed model, based on the idea that a necessary condition for electrochemical corrosion is the presence of short-circuited microgalvanic elements on the metal surface, is erroneous. When considering electrochemical corrosion from the positions of this model, the use of polarization diagrams to study corrosion processes is not legitimate.

General theory of anodic oxidation of silicon and its compounds (analytical review)

The identity of the mechanisms of anodic oxide films formation on silicon, silicon carbide, and silicon nitride is proved, which can be used as the basis for the General theory of anodic oxidation of these materials. The processes of galvanostatic anodic oxidation of Si, SiC and Si3N4 in the intervals of linear dependence of the formation voltage on time proceed with activation control. The limiting stages in all cases are the anodic reactions of the formation of intermediate SiO monoxide. Preference should be given to electrolytes with lower values of the potential environmental hazard criterion of the electrolyte, which have a higher degree of environmental safety.

Influence of Humidity on Performance of Single Chamber Air-Cathode Microbial Fuel Cells with Different Separators

The maximum performance of microbial fuel cells (MFCs) is significantly affected by the reduction reactions in the cathode, but their optimum condition is not fully understood yet. The air-cathode MFC operations with different separators (Nafion 117 and polypropylene (PP80) were evaluated at various relative humidity (RH) at the cathode chamber. Air cathode MFCs with a Nafion 117 separator at RH of 90 ± 2% produced the highest cell voltage of 0.35 V (600 Ω) and power density of 116 mW/m2. With a PP80 separator, the maximum power generation of 381 mW/m2 was obtained at a relatively lower RH of 30 ± 2%. The cyclic voltammogram and Tafel analysis indicated that the best performance of cathodic oxygen reduction reactions could be observed at 90% RH for Nafion and 50% RH for the PP80 separator. Additionally, the RH conditions also affected the anodic reactions and oxygen mass transfer rates to the anode chamber through the cathode and separators. This study suggests that the optimum RH condition at the cathode is important in order to obtain a high performance of MFC operations and needs to be controlled at different optimum levels depending on the characteristics of the separators.

Ammonium as a Carbon-Free Electron and Proton Source in Microbial Electrosynthesis Processes

Biogas upgrading to biomethane with microbial electrosynthesis (MES) is receiving much attention due to increasing biomethane demands and surplus renewable energy. Research has demonstrated the feasibility of MES to increase methane yield by reducing CO2 in anaerobic digestion (AD). Such CO2 reduction occurs at the cathode and requires the supply of both protons and electrons. The most studied sources of protons and electrons are oxidation of organic substances and water, generated at the anode. These anodic reactions, however, also imply the production of CO2 and O2, respectively, both with negative implications for the AD process. A source of protons and electrons without CO2 and O2 as by-products would be beneficial for MES-enhanced biomethane production. This opinion article discusses the possibility of ammonium to serve as a sustainable proton and electron source.