Tafel Extrapolation Research Articles

Multilayered NiMo/CoMn/Ni Cathodic Electrodes with Enhanced Activity and Stability toward Alkaline Water Electrolysis.

In this study, multilayered NiMo/CoMn/Ni cathodic electrodes were prepared by the multilayered electrodeposition method. The multilayered structure includes a nickel screen substrate, CoMn nanoparticles at the bottom, and cauliflower-like NiMo nanoparticles at the top. The multilayered electrodes have a lower overpotential, preferable stability, and better electrocatalytic performance than monolayer electrodes. In a three-electrode system, the overpotentials of the multilayered NiMo/CoMn/Ni cathodic electrodes at 10 and 500 mA/cm2 are only 28.7 and 259.1 mV, respectively. The overpotential rise rate of the electrodes after constant current tests at 200 and 500 mA/cm2 was 4.42 and 8.74 mV/h, respectively, and the overpotential rise rate after 1000 cycles of cyclic voltammetry of the electrodes was 1.9 mV/h, while the overpotential rise rate after the three stability tests of the nickel screen was 5.49, 11.42, and 5.1 mV/h. According to the Tafel extrapolation polarization curve, the Ecorr and Icorr of the electrodes were -0.3267 V and 1.954 × 10-5 A/cm2, respectively. The charge transfer rate of the electrodes is slightly slower than that of the monolayer electrodes, indicating that its corrosion resistance is more excellent. An electrolytic cell was designed for the overall water-splitting test, and the current density of the electrodes was 121.6 mA/cm2 at 1.8 V. In addition, the stability of the electrodes is excellent after intermittent testing for 50 h, which can greatly reduce power consumption and is more suitable for industrial overall water-splitting tests. In addition, the three-dimensional model was used to simulate the three-electrode system and alkaline water electrolytic cell system, and the simulation results are consistent with the experimental results. The hydrogen adsorption free energy (ΔGH) of the electrodes was -1.0191 eV, which was evaluated by density functional theory (DFT). The ΔGH is closer to zero than that of the monolayer electrodes, indicating that the surface has stronger adsorption of hydrogen atoms.

Ceramic Coating for High Temperature Corrosion Protection of Steel

Abstract: In high temperature environments where oxidation occurs which effects the metal in multiple ways. High temperature corrosion is typically seen in ductile steel. This can cause abrupt failure and reduce a metal's mechanical properties. A variety of ceramic coatings are available that can be applied to enhance functionality and prevent corrosion, particularly at high temperatures. The majority of ceramic coatings are typically electrically nonconducting, making them excellent insulators. It also has a high melting temperature of up to 4000⸰F and remarkable abrasion resistance. Due to these characteristics, they offer exceptional corrosion resistance and strong abrasion resistance in high temperature conditions. In this research, the team synthesize ceramic coating which may provide exceptional abrasion resistant as well high temperature oxidation resistance. Before selecting the ingredients, it needs to be examined the compatibility between mild steel (sample) and constituents of ceramic coating, majorly the thermal expansion characteristics. It must be identical otherwise fractures can be produced on the coated surface of a metal. Samples were made as per demand, following collecting a sample and cleaned accurately to attach the coating appropriately. After application of coating on sample it should place in furnace which promote diffusion on a metal surface and construct protective barrier. Further, dipping the sample in 3.5% NaCl solution for 21 days and execute the OCP and EIS test of naked sample and coated sample correspondingly for 5 days. Potentiostat provides several graphs viz OCP, Bode plot, Nyquist impedance plot and Tafel Extrapolation. High temperature oxidation resistance of the ceramic covering was investigated using TGA analysis. The weight gain of coated sample is roughly 1mg/cm2 compared to about 4 mg/cm2 for plain sample in TGA curve. This illustrates that the ceramic coating is averting oxidation of steel surface at high temperature of 500ºC.

Effect of different corrosive media on the corrosion resistance and mechanical properties of armor steel

Abstract Armor steel samples were exposed to corrosion for 24, 72, 168, and 720 h in two different corrosive media. The corrosion rate was determined using mass loss, measurement of the concentration of components in the corrosive medium solution, and Tafel extrapolation methods. Before and after corrosion experiments, the tensile properties, surface characteristics, and phase structures of the samples were examined. The surface analyses were performed using the SEM technique combined with EDX analyses, and the phase analyses were performed by X-ray diffraction. The corrosion rate determined by the mass loss method was 0.02 ± 0.01 mm year−1 for the 3.5 wt% NaCl medium and 2.66 ± 0.16 mm year−1 for the 1 M HCl medium. The corrosion rate values determined by the Tafel extrapolation method were 0.02 ± 0.01 mm year−1 in the 3.5 wt% NaCl medium and 1.21 ± 0.01 mm year−1 in the 1 M HCl medium. There was a decrease in the tensile, yield strengths, and elongation to fracture values of the corroded samples compared to the non-corroded samples. While intergranular ductile fracture occurred in samples exposed to 3.5 wt% NaCl medium, there were features reminiscent of the brittle fracture in samples exposed to the 1 M HCl/168 h medium.

Investigation of the electrochemical behavior of titanium dioxide coating on magnesium alloy

Biocompatibility and electrochemical corrosion resistance are one of the most important issues in bone implants. In the last decades, metal implants have received much attention because of their properties. Magnesium and its alloys have been widely used in orthopedics because of their biocompatibility and bone growth proprieties. Magnesium has low corrosion resistance; especially in biological environments of the body, or when exposed to blood plasma, this makes magnesium useful as an absorbable implant. To increase the corrosion resistance of magnesium alloys, and adjust the corrosion rate of the implant to the rate of bone growth, it is necessary to coat these implants. Ceramic coatings are one of the possibilities, because of their biocompatibility and high corrosion resistance. TiO2 possesses desirable properties, such as an excellent mechanical features, high corrosion resistance, and biocompatibility, which make it widely used as implant coatings material. Sol-gel is one of the effective methods for making various ceramic materials. In this study, the electrochemical properties of magnesium alloy Mg-5Gd-2.5Nd-0.5Zn-0.5Zr with and without coating with phosphate-buffered saline (PBS) are investigated through Tafel extrapolation and impedance test Titanium dioxide coating was applied to the alloys by the sol-gel method. The effect of four variables of fluoride ion content, etching time, immersion time, and the number of immersions were studied. The results of SEM images showed the optimal sample surface of a uniform coating with a thickness of 6 μm. The optimal sample corrosion current density reported 2.58 × 10−5 A/m2, which is the lowest current density in samples. The results of the impedance test also confirmed these data and the optimal sample indicated the highest value of Rp = 5003 Ω.cm2.

A green vanadium-based formulation for the conversion of steel

ABSTRACT The electroless deposition of a novel vanadium-based conversion coating (VCC) on carbon steel was investigated varying parameters as vanadium salt concentration, immersion time, bath pH and temperature. The novelty resides on the deposition of a protective layer from a V4+ solution comprising green reducing agents like ascorbic and citric acids. The VCC was found to be amorphous, composed by closely packed particles rich in vanadium oxides/hydroxides. Corrosion resistance was evaluated by linear polarization resistance, Tafel extrapolation and electrochemical impedance spectroscopy. Such conversion coating provided an optimum corrosion performance for steel substrates immersed in sulphates and chlorides rich solutions. An optimum was achieved with a 0.1 M KVO3 solution held at 45°C, at pH = 3 and a deposition time of 10 min. Higher values of the latter parameters did not provide any further improvements: the formation of cracks during the dehydration process compromised the coating integrity.

Corrosion Resistance of Nanostructured Cemented Carbides with Alternative FeNi and FeNiCo Binders.

Nanostructured cemented carbides with Co binders have shown excellent mechanical properties in various applications. Nevertheless, their corrosion resistance has shown to be insufficient in different corrosive environments, leading to premature tool failure. In this study, WC-based cemented carbide samples with different binders were produced using 9 wt% of FeNi or FeNiCo with the addition of Cr3C2 and NbC as the grain growth inhibitors. The samples were investigated using electrochemical corrosion techniques: the open circuit potential Ecorr, the linear polarization resistance (LPR), the Tafel extrapolation method, and the electrochemical impedance spectroscopy (EIS) at room temperature in the solution of 3.5% NaCl. Microstructure characterization, surface texture analysis, and instrumented indentation were conducted to investigate the influence of corrosion on the micro-mechanical properties and the surface characteristics of the samples before and after corrosion. The obtained results indicate a strong binder chemical composition's effect on the consolidated materials' corrosive behavior. Compared to the conventional WC-Co systems, a significantly improved corrosion resistance was observed for both alternative binder systems. The study shows that the samples with the FeNi binder are superior to those with the FeNiCo binder since they were almost unaffected when exposed to the acidic medium.

Comparison of the Mechanical Properties and Corrosion Resistance of the Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN Coatings

In this work, the mechanical properties and corrosion resistance of Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN coatings deposited by the physical vapor deposition (PVD) method on Ti-6Al-4V alloy were compared. The phase composition of the coatings, their hardness and fracture resistance in scratch tests were determined, and their structural characteristics were also studied using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The diffraction spectra were made using an automatic X-ray diffractometer. The value of the adhesive component of the friction coefficient fadh of the pair “coated and uncoated Ti-6Al-4V alloy” was investigated in the temperature range of 20–900 °C. The lowest value of fadh was detected for the Zr-ZrN coating at temperatures below 400 °C, while for the Mo-MoN coating it was observed at temperatures above 700 °C. The polarization curves of the coated and uncoated samples were performed in a 3% aqueous NaCl solution. The level of corrosion of the Ti-6Al-4V alloy samples with Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN coatings was evaluated using the Tafel extrapolation method, the iteration method, and the polarization resistance method. The results obtained with these methods indicate that the Zr-ZrN coated sample has the best corrosion resistance in the 3 wt.% NaCl solution, with a corrosion current density of 0.123 μA/cm2.

Synthesis of hexagonal boron nitride based PANI/h-BN and PANI-PPy/h-BN nanocomposites for efficient supercapacitors

Conducting polymers based hexagonal boron nitride (h-BN) nanocomposites i.e. polyaniline (PANI)/h-BN and polyaniline -polypyrrole (PANI-PPy)/h-BN were fabricated through chemical oxidative polymerization approach. The structural, thermal, morphological, and electrochemical properties of the prepared materials were studied extensively. FTIR and XRD patterns revealed the successful fabrication of desired nanocomposites. TGA analysis showed that the presence of h-BN increases the thermal stability of both the nanocomposites (PANI/h-BN and PANI-PPy/h-BN). All the prepared materials demonstrated irregular and aggregated morphological structures with the diameters remained almost similar (100 nm). The electrochemical performance of the materials was evaluated by cyclic voltammetry (CV), electrochemical impedance (EIS) and galvanostatic charge-discharge (GCD) in three electrodes and two electrodes systems. The prepared PANI/h-BN nanocomposites exhibited the highest capacitance (927 F/g) and capacitance retention (97.6%) after 100 cycles compared to the others. The Tafel extrapolation study shows less corrosion rate for PANI/h-BN electrode, and EIS indicate higher energy storage capacity of the PANI/h-BN electrode compared to PANI-PPy/h-BN electrode. Finally, a set of hybrid asymmetric supercapacitor was successfully constructed using the synthesized nanocomposites as positive electrode and activated carbon (AC) as negative electrode. The assembled device PANI/h-BN//AC showed the highest sp. capacitance (343 F/g), power density (921 W/kg), and it lit up a 5 mm green LED for 200 min, indicating its superiority over the other supercapacitor device.

Corrosion and material properties of 316L stainless steel produced by material extrusion technology

Material Extrusion (ME) multi-step additive manufacturing of highly filled metal filament Ultrafuse 316L offers a notable alternative to cutting-edge additive technologies of metal alloys. It allows the creation of metal objects with debinding and sintering processes. Especially Powder Bed Fusion (PBF) technologies using laser or high-energy electron beams require costly maintenance, professional operators, and demanding process conditions during printing. On the other hand, such requirements do not incorporate ME printing.This study aims to comprehensively investigate and describe the behavior of material printed out of Ultrafuse 316L stainless steel filament on an affordable ME office-friendly printer. The main focus was on tests of fracture toughness, porosity, and corrosion resistance determined by the Tafel extrapolation method. The secondary objective was verifying the mechanical properties found in other studies (differing in results). For this purpose, several sets of fully dense samples were printed, debinded, and tested.

Corrosion Inhibition of Medium Carbon Steel in the Acidic Medium Using Alcoholic and Aqueous Extract of Kujarat Tea Plant

This study deals with the corrosion inhibition of metal corrosion process of medium carbon steel using 1M HCl for kinetic studies and rate reaction determination. The weight loss method is applied to pieces of Medium carbon steel divided to Cubans with dimensions (0.4*2*2.4) cm , and use Tafel Extrapolation Method, the samples were polished using carbide silicon paper with dimensions of (180,200,400,600,800,1000). The samples were immersed in the alcoholic medium ethanol at a temperature 293K for 3hr. Natural inhibitor Kujarat Tea (Hibiscus sabdarriffa L.) is used which is extracted in aqueous and alcoholic medium, different concentrations (1000،2000, 3000) ppm have been used ; The best concentration found through the results is a concentration found that is 1000 and 2000 ppm, the results indicate that the highest degree of inhibition for aqueous extract is 93.3% with the concentration of 2000 ppm and 90.5% with 1000 ppm at293K. While the alcoholic inhibitor shows the highest efficiency 92.4% with a concentration of 2000 ppm and 88.6% with a concentration of 1000 ppm respectively. The structure of the inhibitor was investigated using infrared spectroscopy (FTIR), and the surface morphology of the tested samples was investigated using a scanning electron microscope (SEM).

Uticaj ekstrakta polka maline (Rubus idaeus L.) na inhibiciju korozije bronze

Plant extracts contain a large number of organic compounds, and one of the large groups of compounds present are phenolic compounds. Researchers have shown that a certain number of these compounds can be used as effective metal corrosion inhibitors. Plant extracts of raspberries (leaves, flowers, and fruit) were obtained by ultrasonic extraction using 96% ethanol as a solvent. The UV/Vis spectrophotometric method was used to determine the content of total phenols in plant extracts. Phenolic acids and flavonoids in plant extracts were separated and quantified using the HPLC method. Tafel extrapolation was used for electrochemical characteristics. The corrosion characteristics and behavior of bronze in 3% NaCl solution, with and without the presence of plant extracts were investigated. The content of total phenols in leaves was found to be 107.14±3.63 mg/g in flowers 148.99±9.02 mg/g and in fruits was 8.75±0.61 mg/g. Leaf extract in a concentration of 0.04828 g/L according to the Tafel extrapolation method provides the best protection for bronze in a 3% NaCl solution. The same concentration in the case of flower and fruit extracts proved to be the most favorable.

Development of Ni-Co-CNT composite coatings for corrosion protection of mild steel in 5% NaCl

In this report, corrosion resistance of Ni-Co-CNT composite coatings on mild steel was studied. The deposition step follows composite-electrodeposition technique. The effect of CNT nanoparticle on corrosion resistance behavior of Ni-Co alloy coatings on mild steel were studied. The Ni-Co bath contents such as electrolytes, stabilizer and additives were optimized by using Hull cell. The optimized amount of CNT particle in the bath was found to be 0.5g/L. The surface modification of Ni-Co alloy coatings in the presence of nanoparticle was studied interms of their corrosion resistance behavior. The Ni-Co-CNT composite coatings was developed at different current densities. The corrosion protection efficacy of the deposited coatings has been studied by using Tafel extrapolation and electrochemical impedance techniques. The Ni-Co-CNT coating was found to be more stable and results showed linear change of potential with time. The result depicted that deposited composite coating on mild steel at a current of 4.0Adm −2 was found to be more corrosion resistance as compared with other current density coatings. This was attributed to decrease of size of the particle with increase of current densities as confirmed by AFM analysis. The chronopotentiometry technique revealed that coating was found to be more stable for several hours at different current densities. The coating obtained at a c.d of 4.0A dm −2 was found be more stable towards corrosion and confirmed by Chrono potentiometric techniques.

Investigation of Inhibitory Effect of the Rubus idealis L. Extract on Corrosion of Copper

The aim of this work was to examine the impact of raspberry extract (Rubus idaeus L.) on copper corrosion characteristics. The raspberry leaf extract was prepared using Soxhlet extraction with ethanol as solvent. The estimation of the total polyphenol content in the obtained sample was determined by UV/Vis spectrophotometric method. The identification and quantification of phenolic acids was performed using HPLC analytical method.In addition, the aim of this work was to examine the impact of individual phenolic compounds (rutin, gallic acid, quercetin, and catechin hydrate) on the corrosion properties of copper. . , The corrosion rate of copper with the extract of the raspberryleafof the Polkavariety was tested. A copper corrosion test was performed in a 3% NaCl solution without and in the presence of the extract. The copper polarization resistance (Rp) values in 3% NaCl solution without and in the presence of the extract weredetermined by the linear polarization method. The corrosion behavior of copper in 3% NaCl solution without and in the presence of extract was determined by specific electrochemical parameters: corrosion potential (Ecorr), corrosion current density (Icorr), and slopes of the anode (βa) and cathode (βk). The electrochemicalimpedance spectroscopy method was used to examine the corrosion behavior of copper in 3% NaCl solution without and in the presence of extract. The results obtained by Tafel extrapolation showed that the corrosion rate decreases in the presence of the tested extract. Studies conducted by the electrochemical impedance spectroscopy method show that the tested extract slows down the kinetics of the corrosion process, which is visible through an increase in resistance. The results confirm that the examined extract can be used for protection in an aggressive medium, such as a 3% NaCl solution.

Ptychostomum schleicheri (Bryophyta) Ekstraktının Yumuşak Çeliğin Korozyonu Üzerine Yeşil Önleyici Etkisi

In present study, the inhibitive impact of Ptychostomum schleicheri extract, a moss species of Bryaceae family, on the mild steel corrosion in 1 M HCl at ambient temperature was firstly analysed by Tafel extrapolation method, electrochemical impedance spectroscopy (EIS) and linear polarization (LPR) techniques. Electrochemical tests were conducted by 1 h immersing mild steels in HCl solutions containing four various concentrations of moss extract. At a concentration of 0.200% (w/v), the moss extract displayed around 90 percent inhibition efficiency by three electrochemical methods, and it was also observed that its protective effect increased depending on the upsurge in the concentration of Ptychostomum schleicheri extract. The morphologies of mild steels surface in 1 M HCl with and without P. schleicheri extract at the end of 1 h immersion time were visualized by a metal microscope. Finally, according to the electrochemical data and surface morphology results, it can be said that the extract molecules adsorbed on the mild steel surface to achieve almost maximal coverage and contact.

Computational modelling and theoretical calculations on hydroxy citric acid and mangostine and comparing the corrosion inhibition effect of aqueous and alcoholic extracts Garcinia cambogia leaves for mild steel in hydrochloric acid

The utility of Garcinia cambogia leaves aqueous and alcoholic (GCLW and GCLA) extracts were used as a green candidate for mitigating the mild steel corrosion in 0.5N HCl solution. The protective efficiency was monitored electrochemically and theoretically using different soft wares including Gaussian09, Biovia material studio, and also with Fukui function analysis procedure from D Mol 3 calculations. The preliminary phytochemical screening of active components of the extracts were done using IR and UV-Visible spectral studies. Mangostine and hydroxy citric acid (HCA) were identified as the active constituents of the extracts and their presence on the metal surface after inhibition is confirmed using XPS elemental analysis. The increased activity of the aqueous extract may be due to the increased percentage of HCA in the water extract than the alcoholic counterpart. 4V/V% GCLW has 84 % efficiency at room temperature whereas the same volume percentage alcoholic extract has only 81% efficiency. The inhibition efficiency decreases with rise in temperature suggesting the physical mode of adsorption of the inhibitor system on the metal surface. But the results of computational modelling suggest chemisorption resulted from the donation of electron pairs from O22, H46, and H38 of mangostine and O12 of HCA. This bond is strengthened by the back acceptance of electron pairs from the filled metal orbital to C2 of mangostine and O3 of HCA. Tafel extrapolation studies suggest mixed type inhibition nature for both GCLW and GCLA with anodic prominence. Thermodynamic adsorption suggests the Langmuir monolayer model for GCLW and Temkin model for GCLA.

Characteristics of boronized Ti6Al4V alloy using boric acid based boronizing mixture

Boronizing processes of Ti alloys are generally performed in atmosphere-controlled furnaces. In this study, it is aimed to carry out boronizing process under atmospheric conditions by using an alternative boronizing mixture containing boric acid and to better the surface characteristics of Ti6Al4V alloy by boronizing. The efficiency of the boronizing mixture was evaluated by performing boronizing at different process temperatures (900-1100 °C) and durations (12 and 20 h). Microstructural (OM, SEM) and chemical (XRD, EDS, XPS) analyzes were performed to characterize the boride layers formed on the surfaces of the boronized samples. As a consequence of these analyzes, it was found out that a two-phase boride layer (TiB2 + TiB) was obtained in the samples. In addition, in vitro tests were done for specifying the bioactivity of boronized samples. In order to determine the effect of boronizing on the corrosion resistance of Ti6Al4V alloy, corrosion tests were performed by the Tafel extrapolation method. The adhesion behavior of the boride layers was determined by the Daimler-Benz Rockwell C indentation test. As a result, boronizing studies have been performed successfully without atmospheric-controlled conditions and it has been defined that surface characteristics of the Ti6Al4V alloy have bettered through the boride layers formed on the alloy surface.

Comparative study on electrochemical corrosion behavior of boronized X52 steel in 1 M HCl and H2SO4 solutions

This paper investigates the effect of boronizing treatment on the corrosion resistance of API X52 steel. Borides were grown on API X52 steel in a powder mixture containing 5% B4C as a boron source, 5% NaBF4 as an activator, and 90% SiC as diluents for 4 hours at 950 °C. X-ray diffraction (XRD) analysis revealed that the sample's boride layer contains only Fe2B phases. The corrosion behavior of borided and unborided specimens was investigated using the Tafel extrapolation method in 1M HCl and H2SO4 solutions. The results show that borided specimens have better corrosion resistance than unboronized specimens. The formation of layers of protective iron borides reduces the corrodability of the steel in the borided specimens. Boronizing increased the corrosion resistances of X52 steel in HCl and H2SO4 by 23 and 77-fold, respectively.

Effect of Bias Voltage on Adhesion and Corrosion Resistance of Titanium Nitride Coated Stainless Steel Substrate

In this work, the adhesion and corrosion resistance of TiN coating by magnetron sputtering on stainless steel substrates under different bias voltages conditions (-50 V and-100 V) was investigated. AFM was used for surface roughness and grain size analysis, XRD for phase identification, Rockwell C for adhesion and nanoindentation for hardness and elastic modulus. According to AFM the coating deposited at-100V bias had decreased surface roughness, the value decreased from 2.7 nm (for-50V sample) to 1.8 nm, this was due to an etching like process which occurs when ions with higher energies start hitting the surface. The coated samples came under HF1 adhesion parameter which is the highest class of adhesion in the model on the basis of Rockwell C adhesion test. nanoindentation hardness and elastic modulus results of-50 V and-100V were found to be 224 GPa and 182 GPa, respectively and the value of hardness, 16 GPa and 22 GPa, respectively. The corrosion behavior of TiN coatings were studied in 3.5wt. % NaCl solutions using Tafel Extrapolation, Cyclic Polarization and Open Circuit Potential. It was noted on the basis of these corrosion tests that, as bias voltage is increased, it leads to the formation of more densely packed, fine grained columnar structures with less pores, which decreases the chances of corrosion. .

Composite Coatings of Chitosan and Silver Nanoparticles Obtained by Galvanic Deposition for Orthopedic Implants.

In this work, composite coatings of chitosan and silver nanoparticles were presented as an antibacterial coating for orthopedic implants. Coatings were deposited on AISI 304L using the galvanic deposition method. In galvanic deposition, the difference of the electrochemical redox potential between two metals (the substrate and a sacrificial anode) has the pivotal role in the process. In the coupling of these two metals a spontaneous redox reaction occurs and thus no external power supply is necessary. Using this process, a uniform deposition on the exposed area and a good adherence of the composite coating on the metallic substrate were achieved. Physical-chemical characterizations were carried out to evaluate morphology, chemical composition, and the presence of silver nanoparticles. These characterizations have shown the deposition of coatings with homogenous and porous surface structures with silver nanoparticles incorporated and distributed into the polymeric matrix. Corrosion tests were also carried out in a simulated body fluid at 37 °C in order to simulate the same physiological conditions. Corrosion potential and corrosion current density were obtained from the polarization curves by Tafel extrapolation. The results show an improvement in protection against corrosion phenomena compared to bare AISI 304L. Furthermore, the ability of the coating to release the Ag+ was evaluated in the simulated body fluid at 37 °C and it was found that the release mechanism switches from anomalous to diffusion controlled after 3 h.

Investigation of carbon steel corrosion by oilfield nitrate- and sulfate-reducing prokaryotes consortia in a hypersaline environment.

Microbiologically influenced corrosion (MIC) behavior of the AISI 1020 carbon steel caused by consortia of nitrate-reducing prokaryotes (NRP) and sulfate-reducing prokaryotes (SRP) was investigated separately in hypersaline seawater conditions. Microbiological analysis, surface images, characterization of corrosion products, weight loss, and electrochemical measurements were employed to monitor the corrosion process for 10days at 40°C. Compared to abiotic corrosion (control), the extent of corrosion was more aggravated in the conditions with microbial consortia. It corroborates the critical role of microbial activity in corrosion processes in natural and industrial environments since microorganisms are widely spread. Corrosion rates obtained from Tafel extrapolation were statically equal for both microbial consortia (0.093 ± 0.009mm.y-1); however, the maximum pit depth on the steel surface subjected to NRP-MIC was about 25% deeper (48.5µm) than that caused by SRP-MIC (32.6µm). In contrast, SRP activity almost doubled the number of pits on the steel surface (2.7 × 104 ± 4.1 × 103 pits.m-2), resulting in more weight loss than NRP activity. In addition, SRP cells formed nanowires to support direct electron uptake from steel oxidation. This research contributes to the understanding of steel corrosion mechanisms in hypersaline environments with the prevalence of NRP or SRP, as oil reservoirs undergo nitrate injection treatments.