Corrosion Science Research Articles

(Invited) Surface Analytical Study of Adsorption Mechanisms of 2-Mercaptobenzothiazole and 2-Mercaptobenzimidazole Corrosion Inhibitors on Cu

The corrosion of metals and alloys is an important issue in industrial applications with an annual global cost estimated to be about 3% of the global GDP (2013). In order to mitigate corrosion, inhibitors are widely used and developed including on copper, a metal which is widely used for its high thermal and electrical conductivity but not totally immune against corrosion.In this work, 2-mercaptobenzothiazole (2-MBT) and 2-mercaptobenzimidazole (2-MBI) [1-2], two structurally related molecules already known for their inhibitory action against corrosion of copper, were studied. The objective was to understand the interaction mechanisms of these two corrosion inhibitors with copper in a well-controlled environment and their influence on the reactivity of copper.To this end, 2-MBT and 2-MBI were dosed at room temperature on a model copper surface, Cu(111), by ultra-low pressure (~10-9 mbar) gas evaporation in ultra-high vacuum conditions. The surfaces were characterized by X-ray Photoelectron Spectroscopy (XPS) and Scanning Tunneling Microscopy (STM) at various growth stages of the inhibitor layer. Thermal stability of the adsorbed molecular layers was also investigated.Growth of molecular layers for 2-MBT and 2-MBI was evidenced on Cu(111) in metallic state with the formation of a monolayer at 5–10 L (1 L = 1×10-6 Torr·s) and multilayers at higher exposure. An excess of sulfur was observed by XPS, with a S 2p component at the same binding energy as atomic S bonded to Cu, indicating a partial decomposition of the molecules at the initial stages of adsorption. STM characterization at low exposure (3–4 L) revealed locally ordered triangular structures for 2-MBT on Cu(111), which can be attributed to atomic S and S of the molecule bonded to Cu, and flat-lying molecules in the multilayer. While adsorption of 2-MBI leads to the formation of an ordered monolayer with different organizations including a (√7×√7)R19.1° structure, which may be attributed to the adsorption of atomic S. Molecules in the monolayer and multilayer are also lying flat. The thickness of the molecular layers was calculated from XPS attenuation to be of the order of several nanometers.The pre-adsorbed molecular layers were observed to markedly decrease the reactivity of copper towards oxygen. Annealing of the molecular layers to above 100°C leads to a partial decomposition and desorption of the inhibitors, and the formation of (√7×√7)R19.1° structure.This study brings new insight into the corrosion inhibition mechanisms of 2-MBT and 2-MBI on copper, which contributes to the knowledge-based development of more efficient corrosion inhibitors for the corrosion protection of copper and its alloys. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC Advanced Grant CIMNAS no. 741123). [1] M. Petrovic Mihajlovic, M. Antonijevic, International journal of electrochemical science 10 (2015) 1027-1053.[2] M. Finšgar, D. K. Merl, Corrosion Science 83 (2014) 64-175.

(Invited) Relationship between the Resistivity Profiles Obtained from the Power Law Model and the Physico-Chemical Properties of Passive Films

Passive film (PF) could be considered a particular nanomaterial with its growth, chemical composition, microstructure, performance and evolution of its performance. The understanding of the film construction, its maintenance and its resistance is the result of a total complementarity between characterization from enhanced physico-chemical analysis techniques, especially those developed by P. Marcus and his group[1], and electrochemical measurements, mainly the electrochemical impedance spectroscopy (EIS).EIS gives access to the capacitive and resistive properties of the passive film. The first, complemented by the Mott-Schottky theory, allows a quantitative approach of electronic properties (semi-conductivity) and the maintenance process of passive films. The second involves the corrosion resistance of the film. Nevertheless, it is important to make a rigorous adjustment of the parameters resulting from the impedance diagrams. An adjustment that takes into account the physical meaning of parameters, especially for the analysis of the constant phase elements (CPE) used in the treatment of the diagrams that present one depressed semicircle [2]. The knowledge of the oxi-hydroxide character of the PF, evidenced from physicochemical characterizations, allows considerations of the spatial distribution of the heterogeneities (3D) within the thickness of the PF from the variation of its resistivity obtained from the Power Law Model (PLM)[3,4]. In fine, the resistivity profiles give information about interface reactivity and distribution of species along the thickness of the passive layer.The use of the PLM requires the assessment of several parameters, especially a and Q defining the CPE or the thickness of the PF, which is generally assessed by physicochemical measurements. Most of them can be determined by advanced graphical analysis of impedance diagrams[5,6]. It can then be used to guide the adjustment of the diagrams by inputting known parameters into the model.To exemplify the interdependency between physicochemical analysis and electrochemical impedance measurements, two studies illustrate the contribution of in-depth analyses of the resistivity profiles for two passive materials. That will be the opportunity to highlight which information can be drawn and finally, to propose reaction mechanism.First of all, the passivity of the Ni-20Cr alloy has been studied in different solutions[7]. In this work, the electrochemical impedance diagrams have been successively performed under applied potential in passive region. From PLM analysis, it was observed that the evolution of the resistivity at the Ni-20Cr/PF interface explains the evolution of the current density during polarization. The resistivity profiles obtained for increasing applied potentials on the passive plateau showed a decrease of the resistivity plateau at the substrate/PF interface and an increase of the resistivity at the PF/electrolyte interface, highlighting the modification of the passive film according to the anodic polarization.The second example concerns 316L stainless steel immersed in a 0.02M sodium sulphate solution and under proton irradiation[8]. It was shown that the impedance diagrams obtained before and after irradiation were almost superimposed, suggesting that the system was reversible. However, the resistivity profiles showed that under irradiation, the resistivity at the PF/electrolyte interface decreased and reached its initial value after irradiation. On the other hand, the length of the plateau at 316L/PF interface disappeared during irradiation and was reduced after irradiation by comparison with before irradiation.The case studies presented show that the advances proposed in the analysis of impedance diagrams, combined with physicochemical analyses, provide a global knowledge of passivation mechanisms. Maurice, P. Marcus, Current opinion in solid state & material science, 22 (2018) 156-167.Tribollet, V. Vivier, M.E. Orazem, in Encyclopedia of Interfacial Chemistry (2018), Ed. Elsevier, 93-107.B Hirschorn, M. E. Orazem, B. Tribollet, V. Vivier, I. Frateur, M. Musiani, Journal of the Electrochemical Society 157 (2010) C452-C457.B Hirschorn, M. E. Orazem, B. Tribollet, V. Vivier, I. Frateur, M. Musiani, Journal of the Electrochemical Society 157 (2010) C458-C463.E. Orazem, N. Pébère, B. Tribollet, Journal of the Electrochemical Society 153 (2006) B129-B136.Benoit, C. Bataillon, B. Gwinner, F. Miserque, M. E. Orazem, C. M. Sánchez-Sánchez, B. Tribollet, V. Vivier, Electrochimica Acta 201 (2016) 340-347.Zhang, B. Ter-Ovanessian, S. Marcelin, B. Normand, submitted to Electrochimica Acta.Normand, N. Bererd, P. Martinet, S. Marcelin, M. Moine, J. Ferreira, D. Baux, T. Sauvage, N. Moncoffre, submitted to Corrosion Science.

(Invited) Atmospheric Corrosion of Magnesium Alloys: Influence of Aluminium Content

Magnesium has gained considerable interest as a structural material for automotive and aerospace applications due to its low density and high specific strength. The use of magnesium alloys in engineering applications is, however, mainly limited by their unsatisfactory surface properties and their poor corrosion resistance. In recent years, significant improvements have been made in achieving a better corrosion resistance particularly by reducing the contents of impurities such as Fe, Cu, and Ni. Intermetallic phases, a result of the casting process, play an important role in the corrosion process. The role of these intermetallic phases has been addressed in a number of papers [1–3]. The role of aluminum in the atmospheric corrosion of magnesium alloys has less addressed in the literature [4]. Esmaily et al have shown recently that the rate of corrosion of magnesium alloys decreased when increasing the Al content. However these experiments were performed on commercial magnesium alloys produced high pressure die casting under constant RH exposure at 90% RH.In our work the corrosion behavior of binary Mg-Al alloys as well as that of commercial magnesium alloys with different aluminum contents have studied both under cyclic corrosion exposure in the laboratory and in field exposures in France and in Vietnam. Analyses of corrosion products have also been conducted. Additional in-situ measurements have been performed in order to better understand the atmospheric corrosion mechanisms of Mg alloys.An important decrease in the maximum pit depth can be observed after different laboratory exposures when increasing the aluminum content in the material. Similar results have been obtained after 9 months exposure in Field. Hence, from these results it is obvious that an increase of the aluminum concentration in Mg-Al alloys decreased the corrosion rate of the alloy. This lead in lower mass loss and less deep corrosion attacks in the magnesium grains. The analyses of corrosion products formed after the cyclic corrosion tests and field exposures revealed the presence of Magnesium carbonate and MgCO3(OH)4,4H20, respectively. In both cases magnesium hydroxide (Mg(OH)2 was also found in the corrosion products. The results will be discussed in relation with the microstructure of the cast materials. O. Lunder, J.E. Lein, S.M. Hesjevik, T.K. Aune, K. Nisancioglu, Werkstoffe und Korrosion 45 (6) (1994) 331–340. O. Lunder, J.H. Nordlien, K. Nisangliou, Corrosion Reviews 15 (3–4) (1997) 439–469.G. Song, A. Atrens, M. Dargusch, Corrosion Science 41 (1999) 249–273.M. Esmailly, D.B. Blucher, J.E. Svensson, M. Halvarson and LG Johansson, Scripta Materiala, 115 (2016), 91-96

Thermochemical stability of delafossite and other relevant ternary phases in the Cu–Fe–S–O–H system

In the present study the stability of the phases pertaining to the Cu–Fe–S–O–H compositional system is investigated using the Eh-pH prevalence diagrams. Calculations were performed under the PHREEQC formalism, simultaneously accounting for all concurrent equilibria. Accordingly, point-to-point mass balance diagrams were realised, changing initial parameters to explore the dependence of the system on the temperature, and on the metal-to-sulfur ratio. Among the most relevant results, discussed in comparison with the previous existing literature mainly driven by calculation performed under the so-called line method approximation, the occurrence of large field of stability of the ternary species (and, among them, of delafossite, CuFeO2) and the net change of some boundaries in the stability fields of the binary species, due to competing equilibria. The results have been discussed on the light of the occurrence of these minerals in cuprous and ferrous mineralizations, and in the perspective of possible application in Corrosion Science.

Segregating the homogeneous passive film and understanding the passivation mechanism of Ti-based metallic glasses

Resolving structural and componential characteristics of passive film is a long-standing challenge in corrosion science since it’s difficult to separate extremely thin passive films. In this work, the passive films are successfully separated from Ti-Zr-Be-Al/Ni/Fe glassy substrates as large-area thin membranes by the designed “Ribbon-Penetration” method. The homogeneous and continuous passive films are identified as a single-layer amorphous structure, whose primary components are TiO2, ZrO2 and BeO. Alloying Ni or Fe element could induce the enrichment of TiO2 in the passive films and improve the structural compactness, resulting in the superior corrosion resistance in 3.5 wt.% NaCl solution.

Improved Corrosion Resistance of Magnesium Alloy in Simulated Concrete Pore Solution by Hydrothermal Treatment.

Magnesium alloys are considered for building materials in this study due to their natural immunity to corrosion in alkaline concrete pore solution. But, chloride ions attack often hinders the application of most metals. Therefore, it is necessary to conduct a preliminary corrosion evaluation and attempt to find an effective way to resist the attack of chloride ions in concrete pore solution. In our study, hydrothermal treatment is carried out to modify Mg-9.3 wt. % Al alloy. After the treatment in NaOH solution for 10 h, scanning electron microscopy (SEM) reveals that a layer of dense coating with a thickness of about 5 μm is formed on Mg alloy. Energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray Diffraction (XRD) are combined to analyze the coating, and it is thereby confirmed that the coating is mainly composed of Mg(OH)2. As expected, both immersion test and electrochemical corrosion test show that the coated magnesium alloy has a better corrosion resistance than the uncoated one in simulated concrete pore solution with and without chloride ions. In summary, it indicates that hydrothermal treatment is a feasible method to improve the corrosion resistance of Mg alloys used for building engineering from the perspective of corrosion science.

Lemon seeds as green coating material for mitigation of mild steel corrosion in acid media: Molecular dynamics simulations, quantum chemical calculations and electrochemical studies

Natural materials are the subject of high priority for corrosion scientists, now a day. Various natural materials have been used to date for corrosion protection of metals. However, their utilizations have been done either in inhibition (mostly) or coating applications (only in composite form). In present work, lemon seed (alone) is used for inhibition as well as coating protection of mild steel (MS) corrosion in acid media. Aqueous extract of lemon seed (ALS) is used as inhibitor, whereas chloroform extract of lemon seed (CLS) is used to form wet (CLSW) and dry (CLSD) coating on MS substrate. Characterizations of ALS, CLSW and CLSD have been done by UV–visible spectroscopy, FTIR spectroscopy, HRSEM, EDAX and AFM analysis. Corrosion testing of both extracts has been performed in 1 M HCl by ac impedance measurements (AIM) and Tafel polarization curves (TPC). The results show that ALS gives very low inhibition of MS corrosion (~45%), while MS coated with CLSD/CLSW provide high efficiency protection (~98%) to the substrate. Theoretical analysis tools, i.e., molecular dynamics simulations and quantum chemical calculations, are also used to determine corrosion properties of lemon seed molecule, which suggest that lemon seed can be prominent material for prevention of MS corrosion.

Corrosion-assisted large-scale production of hierarchical iron rusts/Ni(OH)2 nanosheet-on-microsphere arrays for efficient electrocatalysis

Iron corrosion is always harmful to our industrial manufacture and thus numerous effects have been conducted for corrosion protection. However, the detrimental corrosion may be applied to produce serviceable materials, resulting in “upcycling waste into wealth”. Herein, a novel corrosion engineering is employed to fabricate hierarchical iron rusts/Ni(OH)2 nanosheet-on-microsphere arrays as effective oxygen evolution reaction (OER) electrocatalysts. Through physically mixing the fabricated ultrathin iron rusts with Ni(OH)2 microspheres, the as-prepared catalyst requires an overpotential of only 318 mV to achieve the current density of 20 mA cm−2. Besides, negligible increasement of overpotential is observed after continuous chronopotentiometric determination for 30 h. The excellent OER property is attributed to the formed oxygen bridges of Fe–O–Ni on the solid-solid contact sites, which promote oxidation of Ni2+ specieses via the interfacial Fe3+ of iron rusts (FeOOH). In particular, a large-scale production of 2.968 g iron rusts/Ni(OH)2 catalysts was successfully prepared by using this simple, lowcost yet valid corrosion engineering. This work provides a novel avenue towards large-scale production of efficient OER catalysts by combing with corrosion science, which is beneficial for boosting the progress of water splitting.

Scanning electrochemical cell microscopy: A natural technique for single entity electrochemistry

Scanning electrochemical cell microscopy (SECCM) is a robust and versatile scanning electrochemical probe microscopy technique that allows direct correlation of structure–activity at the nanoscale. SECCM uses a mobile droplet cell to investigate and visualize electrochemical activity at interfaces with high spatiotemporal resolution, while also providing topographical information. This article highlights diverse contemporary challenges in the field of single entity electrochemistry tackled by the increasing uptake of SECCM globally. Various applications of SECCM in single entity electrochemistry are featured herein, including electrocatalysis, electrodeposition, corrosion science and materials science, with electrode materials spanning particles, polymers, two-dimensional materials and complex polycrystalline substrates. The use of SECCM for patterning structures is also highlighted.

Turning Waste into Treasure: Regulating the Oxygen Corrosion on Fe Foam for Efficient Electrocatalysis.

Iron corrosion causes a great damage to the economy due to the function attenuation of iron-based devices. However, the corrosion products can be used as active materials for some electrocatalytic reactions, such as oxygen evolution reaction (OER). Herein, the oxygen corrosion on Fe foams (FF) to synthesize effective self-supporting electrocatalysts for OER, leading to "turning waste into treasure," is regulated. A dual chloride aqueous system of "NaCl-NiCl2 " is employed to tailor the structures and OER properties of corrosion layers. The corrosion behaviors identify that Cl- anions serve as accelerators for oxygen corrosion, while Ni2+ cations guarantee the uniform growth of corrosion layers owing to the appeared chemical plating. The synergistic effect of "NaCl-NiCl2 " generates one of the highest OER activities that only an overpotential of 212 mV is required to achieve 100 mA cm-2 in 1.0 m KOH solution. The as-prepared catalyst also exhibits excellent durability over 168 h (one week) at 100 mA cm-2 and promising application for overall water splitting. Specially, a large self-supporting electrode (9 × 10 cm2 ) is successfully synthesized via this cost-effective and easily scale-up approach. By combining with corrosion science, this work provides a significant stepping stone in exploring high-performance OER electrocatalysts.

CES & T special edition to commemorate the contribution of Professor Brian Cherry to corrosion engineering

Brian Cherry passed away peacefully on 27 April 2018. This Foreword pays tribute to and acknowledges the enormous impact Brian had on the field of corrosion science and technology over many decades...

Non-Destructive, Non-Invasive Noise Measurements for Metallic Lithium Anodes for Lithium Ion Batteries

Electrochemical Noise measurements have been in the spotlight of electrochemical analysis for measurements on stochastic modes of corrosion since the days of Dawson (Hladky and Dawson Corrosion Science 21(4), (1981),317-322). More recently, electrochemical noise measurements for fuel cells and batteries came up as non-invasive and non-perturbing testing methods that can be used for research(Journal of The Electrochemical Society, 165 (11) A2557-A2562 (2018)) and a potential real-time monitoring tool (Denisov et.al. Fuel Cells 17,(2017),225-237).Metallic lithium anodes are currently commercially employed for non-rechargeable batteries (e.g LiSOCl2 or LiMnO2). The main hurdle along the way of implementation in rechargeable batteries is the dendrite formation during the charging process (Cheng, et.al. Chem. Rev. 2017, 117, 10403−10473). The formation of dendrites during charging can lead to catastrophic failure of the batteries including thermal runaway. Though studies on avoiding such failures through either modifying the surface of the electrode and/or the kinetics of deposition are underway, however, as indicated by the review: “more smartly designed in situ or operando techniques are urgently needed to track the process in a working cell”.We have been working on battery noise measurements for the past number of years (Turkish Journal of Chemistry, 42, (2018), 859-868). We have recently shown that the noise of primary Li/MnO2 batteries increase to measurable levels upon suffering a short circuit (Journal of the Electrochemical Society 165(11),(2018),A2557-A2562) and that this is due to the uneven discharge of the metallic lithium anode(Journal of the Electrochemical Society, submitted).In this contribution, we are going to be reporting electrochemical noise as a truly operando method to study dendrite formation. As the measurement requires no modification to the cell (i.e. no windows in the case or the current collectors, no geometry change, not a half cell) and no perturbation in the applied current or the voltage, it is the ultimate non-invasive and non-perturbing method that has the potential to be used as not only a research tool, but also a real-time implementable sensor that can be commercially deployed.As shown in the figure below, using a metallic lithium anode, the noise after a charging attempt with a high current does show an increased noise level due to the uneven formation of dendrites. Figure 1

Diffusion behavior of hydrogen in oxygen saturated and unsaturated plutonium dioxide: An ab initio molecular dynamics study

As the plutonium (Pu) oxides are the crucial issue of the Pu surface and corrosion science and some impurities like hydrogen (H) are virtually impossible to exclude from them in realistic environments, understanding the dynamical behaviors of hydrogen (H) in Pu oxides is essential for the protections and applications of Pu. Here we perform systematic ab initio molecular dynamics (AIMD) calculations to reveal the diffusion behaviors of impurity H in the oxygen saturated (OS) and oxygen unsaturated (OU) Pu dioxide (PuO 2 ). The considered variation ranges of the concentration of interstitial H (θ: H to Pu ratio), the concentration of oxygen vacancy (OV) (n ov : OV to O ratio), and the temperature were 1 32 ∼ 14 32 , 0 ∼ 8 64 , and 300 ∼ 800 K, respectively. The root mean square displacements, radial distribution functions, Bader charge, electronic density of states, and the three-dimensional diffusion coefficients were extracted and analyzed in detail. Results indicate that the H diffusion is inhibited mainly due to the formation of hydroxyl with the host O both in the OS and OU PuO 2 . In the OU PuO 2 the O atoms will transport due to the presence of large concentration of H. The octahedral interstitial site in the OS PuO 2 and the OV in the OU PuO 2 provide a metastable and favorable capturing effect to the interstitial H, respectively. The diffusion coefficient in the OU PuO 2 is smaller than that of in the OS PuO 2 and decreases with n ov essentially as the OV plays the role of a trap for H diffusion. Our conclusions may provide potential guidance for Pu surface and corrosion science. • The mechanisms of inhibit hydrogen diffusion in different plutonium dioxides were confirmed. • Two different capturing effects to hydrogen in saturated and unsaturated PuO 2 were found. • The diffusion coefficients of hydrogen in different plutonium dioxides were obtained. • The variation tendencies of the hydrogen diffusion coefficients were discussed.

Extracting meaningful standard enthalpies and entropies of activation for surface reactions from kinetic rates

While analyses based on the Arrhenius kinetic model have been successfully applied since its introduction, the Arrhenius model neglects to describe pre-exponential factor in a scientifically meaningful fashion. Since the 1930s, transition-state theory (TST), has met with success in interpreting the pre-exponential factor’s value, allowing a standard entropy of activation to be estimated. However, analyses based on TST’s assumptions have been applied inconsistently in the literature, particularly in corrosion science, leading to difficulty in comparison of standard entropy of activations from different studies. In this work, the foundational principles of TST and standard states are discussed and a standard method to apply TST in analyzing rates of surface reactions is recommended. When full details are not available, reacting species’ concentrations should be normalized to the concentration of active surface sites. For corrosion reactions, conversion relationships are given to convert from units of corrosion rate to surface reaction rate, consistent with TST. This method is dubbed a surface reactant equi-density approximation. Application of this standard to reported data results in adjustments of the standard entropy of activation between − 65 and +50 J/mol K and brings reported entropies into a narrower range of values.

Green Corrosion Inhibitors from Agri-Food Wastes: The Case of Punica granatum Extract and Its Constituent Ellagic Acid. A Validation Study

Giving a “new life” to wastes should be the golden rule for all production processes in the forthcoming future, aiming at making them more sustainable and environmentally friendly. In the corrosion science field, the ambitious circular economy paradigm has recently led to the employment of extracts from plants (and, in less extent, from agri-food wastes) as green inhibitors against corrosion of metals. However, in spite of the number of scientific papers published in the field, a deep revision of the scientific approach is needed both in the execution of experiments and in the critical analysis of the results. Starting from some discrepancies in published data, the corrosion inhibition effect induced by a well-characterized methanolic extract from wastes of fermented Punica granatum and by its main component (ellagic acid, EA) was validated. The corrosion behaviour of Armco® pure iron in the presence of small concentrations of ellagic acid and extract (containing ca. 10 µM and 100 µM EA) was studied by combining results from mass loss tests, at free corrosion potential, and from polarization tests, by linearly sweeping the potential applied to the metal substrate. Experiments were carried out both in acidic medium (typical for a general corrosion phenomenon) and in near-neutral chloride bearing solution (characteristic of a localized pitting corrosion phenomenon). Neat conflicts with already published data have been identified first in the solubility of the inhibitor and then in the inhibition efficiency (around 40% in a 0.05 M HCl). The very limited solubility in aqueous environment was identified as the main drawback, hindering any possible exploitation of ellagic acid and pomegranate extract as promising green corrosion inhibitors. Results point to the necessity to establish clear and rigorous good laboratory practices to follow while reporting results on such complex matrices like vegetable extracts.

Metallic Iron for Environmental Remediation: Starting an Overdue Progress in Knowledge

A critical survey of the abundant literature on environmental remediation and water treatment using metallic iron (Fe0) as reactive agent raises two major concerns: (i) the peculiar properties of the used materials are not properly considered and characterized, and, (ii) the literature review in individual publications is very selective, thereby excluding some fundamental principles. Fe0 specimens for water treatment are typically small in size. Before the advent of this technology and its application for environmental remediation, such small Fe0 particles have never been allowed to freely corrode for the long-term spanning several years. As concerning the selective literature review, the root cause is that Fe0 was considered as a (strong) reducing agent under environmental conditions. Subsequent interpretation of research results was mainly directed at supporting this mistaken view. The net result is that, within three decades, the Fe0 research community has developed itself to a sort of modern knowledge system. This communication is a further attempt to bring Fe0 research back to the highway of mainstream corrosion science, where the fundamentals of Fe0 technology are rooted. The inherent errors of selected approaches, currently considered as countermeasures to address the inherent limitations of the Fe0 technology are demonstrated. The misuse of the terms “reactivity”, and “efficiency”, and adsorption kinetics and isotherm models for Fe0 systems is also elucidated. The immense importance of Fe0/H2O systems in solving the long-lasting issue of universal safe drinking water provision and wastewater treatment calls for a science-based system design.

Application of Electrochemical Atomic Force Microscopy (EC-AFM) in the Corrosion Study of Metallic Materials.

Electrochemical atomic force microscopy (EC-AFM), a branch of a scanning probe microscopy (SPM), can image substrate topography with high resolution. Since its inception, it was extended to a wide range of research areas through continuous improvement. The presence of an electrolytic cell and a potentiostat makes it possible to observe the topographical changes of the sample surface in real time. EC-AFM is used in in situ corrosion research because the samples are not required to be electrically conductive. It is widely used in passive film properties, surface dissolution, early-stage corrosion initiation, inhibitor efficiency, and many other branches of corrosion science. This review provides the research progress of EC-AFM and summarizes the extensive applications and investigations using EC-AFM in corrosion science.

Retraction: Self-Healing Performance of Protective Coating with Inhibitor Loaded Nanoparticles of Mesoporous Silica on Copper Alloy (IOP Conf. Ser.: Mater. Sci. Eng. 772 012024)

This article has been retracted by IOP Publishing following an allegation that this work contains significant similarities to another article [1,2].IOP Publishing has investigated in line with the COPE guidelines, and agree this article should be retracted.The authors have admitted this is not their own work. We welcome receiving more information on this matter.IOP Publishing wishes to credit the anonymous whistleblower for bringing the issue to our attention.The authors agree to this retraction.[1] Ma X, Xu L, Lin Z, Li X, and Feng C. ‘Self-Healing Performance of Protective Coating with Inhibitor Loaded Nanoparticles of Mesoporous Silica on Copper Alloy’, (Unpublished manuscript, [Corrosion Science/2017]).[2] Ma X, Xu L, Wei W, Lin Z, Li X. (2017) ‘Synthesis and characterisation of composite nanoparticles of mesoporous silica loaded with inhibitor for corrosion protection of Cu-Zn alloy’. Corrosion Science. 120. 139-147.Retraction published: 27 April 2022

Freestanding anticorrosion hybrid materials based on coordination interaction between metal-quinoline compounds and TiO2-MgO film

Flower-like organic materials have been used for applications in supercapacitors, catalysis, corrosion science, but no report of “flower” from metal-organic compounds on porous inorganic surface has been available. Here, we report the successful fabrication of flowerlike organic-inorganic materials via the combination of TiO2-MgO film prepared on magnesium alloy through plasma electrolytic oxidation (PEO) as inorganic components and metal-quinoline, Na-8-hydroxyquinoline-5-sulfonic acid (NaHQS) and Co(II)-8-hydroxyquinoline-5-sulfonic acid (CoHQS), as the organic component. Interaction between the CoHQS complex and the porous inorganic materials then leads to the formation of flowerlike organic-inorganic coating on the magnesium surface. Furthermore, a detailed analysis of surface morphologies indicates that MHQS molecules are linked together via kinds of intermolecular hydrogen bonds and non-covalent π-π bonds between heterocyclic molecules. PEO-TiO2-CoHQS and PEO-TiO2-NaHQS exhibit enhanced electrochemical performance and chemical stability compared with the free MHQS, which was discussed based on polarization and impedance interpretation. This is attributed to the physical and chemical adsorption on the coating surface as well as the high surface area of the CoHQS in the nanoflowers.

Controlled-Atmosphere Flame Fusion Growth of Nickel Poly-oriented Spherical Single Crystals—Unraveling Decades of Impossibility

Experimental research using monocrystalline electrodes has been a hallmark of interfacial electrochemistry and electrocatalysis since 1980. However, it has been limited to mainly noble metals because of the challenges encountered when using non-noble metals. We report on the development of controlled-atmosphere flame fusion that enables the growth of spherical single crystals of non-noble metals in controlled gaseous atmosphere and without the formation of surface or bulk oxides. The set-up is used to grow nickel single crystals the structure of which is verified using Laue X-ray back-scattering and scanning electron microscopy (SEM). The equilibrium shape of the nickel single crystals calculated using Wulff construction agrees with the actual shape determined using SEM. Electrochemical measurements in aqueous NaOH solution using the monocrystalline Ni electrodes reveal cyclic voltammetry features unique to their surface structure. The methodology, transferrable to other metals, creates enormous research opportunities in interfacial electrochemistry, electrocatalysis, surface science, gas-phase catalysis, and corrosion science.