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Abstract: This paper describes the elaboration of 3-glycidoxypropyltrimethoxysilane (3-GPTMS) films onto AA2024-T3 aluminum alloy for corrosion protection. The dependence of sol–gel morphology on both precipitation under cathodic polarization and nitrate incorporation was investigated via scanning electron microscopy (SEM). Once added into silanization solution, sodium nitrate promoted the reaction of silane condensation and enhanced the film compactness. Electrochemical impedance spectroscopy results (EIS) indicated that doping silane film with NaNO3 ameliorated its barrier property and protectiveness. Silane films applied onto AA2024-T3 surface by using potentiostatic method, exhibited obviously higher corrosion resistance than those obtained by conventional “dip-coating” method. The resistance of coating is accentuated when not very negative potential was applied. [Copyright &y& Elsevier]

Abstract: Bis-1,2-[triethoxysilylpropyl]tetrasulfide silane films containing CeO2·ZrO2 nanoparticles were deposited by dip-coating on galvanised steel substrates. The morphological features of the coated substrates were evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The anti-corrosion performance of the modified silane film applied on galvanised steel substrates was studied by electrochemical impedance spectroscopy (EIS). The ability of nanoparticles to mitigate localized corrosion activity at artificially induced defects was investigated via the scanning vibrating electrode technique (SVET) and by the scanning ion-selective electrode technique (SIET). The results showed that the addition of nanoparticles provides good corrosion protection of the galvanised steel substrates pre-treated with the modified silane solutions. The corrosion activity was reduced by more than one order of magnitude. Complementary d.c. experiments, using zinc electrodes exposed to NaCl solutions containing the nanoparticles were also performed in order to better understand the role of the nanoparticles. An ennoblement of the corrosion potential and polarisation of the anodic reactions could be detected. [Copyright &y& Elsevier]

This work aims to investigate the corrosion resistance of AZ31 magnesium alloy protected by hybrid films based on tetraethylorthosilane (TEOS) and (3-glycidoxypropyl)trimethoxysilane (GPTMS) with the addition of different amounts of SiO 2 nanoparticles. The electrochemical techniques used to evaluate the corrosion resistance in 0.1 mol l l− 1 NaCl electrolyte were open circuit potential (EOC) measurements and electrochemical impedance spectroscopy (EIS), which diagrams were fitted using equivalent electrical circuits (EEC). Surface and cross-section analyses of the bare and coated samples were performed by means of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) before and after electrochemical studies. The results showed that the coatings protected the Mg alloy against corrosion, and that the addition of the nanoparticles improves the corrosion resistance. The morphological characterization showed, for the coated systems, the presence of corrosion products adhered to the metal surface, a process that seems to be hindered in the presence of the SiO 2 nanoparticles. The results demonstrate that an optimum amount of nanoparticles must be added to the coating in order to optimize the anticorrosion protection and that only early stages protection can be achieved. [ABSTRACT FROM AUTHOR]

Highly porous iron‑nickel foams, including the first-ever reported pure iron foam, were prepared by the dynamic hydrogen bubble template electrodeposition method and studied regarding their electrochemical stability and mechanical properties. Changes on the morphology, microstructure, and electrochemical resistance of the foams were investigated as a function of the Fe:Ni ratio by scanning electron microscopy (SEM), d.c. polarization and electrochemical impedance spectroscopy (EIS). Tensile and bending tests were carried out to evaluate the mechanical behavior of the prepared foams. Both crystalline structure and morphology are affected by the increase of Ni content, evolving from a highly porous foam with a body-centered cubic (bcc) structure to a denser material with open pores and face-centered cubic (fcc) structure. Polarization curves reveal an ennoblement of the corrosion potential as the nickel content increases. The impedance response revealed a dependence on the foam porosity. An increased number of pores was found more detrimental to the mechanical properties of the foams, as fractures seem to propagate, preferentially by cracks due to connecting pores. As result, foams with higher Ni contents displayed better mechanical performance for both tensile and bending assays. Results show that this innovative and powerfull technique enables to design iron foams with the adequate properties required for industrial applications. [Display omitted] • Fe and FeNi nanofoams are prepared by Dynamic Hydrogen Bubble Template Electrodeposition. • Pure iron foam is obtained for the first time. • Foams morphology change for higher Ni contents. • Faradaic resistance depends on both %Fe and the pore availability. • Improved mechanical resistance is observed for the less porous foams. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the electrosynthesis of polypyrrole (PPy) onto AA6061-T6 aluminum alloy from a sulfuric acid solution doped with molybdate anions (MoO4 2−) or 8-hydroxyquinoline (8HQ) species. These dopant compounds were chosen as they have been proven to be effective in mitigating the corrosion in chloride medium. The protectiveness of PPy coatings incorporating these corrosion inhibitors within the polymer matrix is discussed. The coatings were morphologically characterized via scanning electron microscopy (SEM) and evaluated electrochemically via polarization in 0.5M NaCl. The results show that doping PPy with molybdates or 8HQ changes its morphological properties and its effectiveness in preventing passivity loss for AA6061-T6 in chloride media. [Copyright &y& Elsevier]

The present work focuses on the self-healing and corrosion behavior of novel epoxy based coatings containing epoxy monomer (EM) and dodecylamine (DDA) as self-healing and corrosion inhibitor, respectively. The coating self-healing ability and the corrosion inhibition effect have been combined, together, in one single coated layer providing autonomous corrosion protection. Towards this goal, the as-synthesized titania nanotubes (TNTs), with an average size of 20 nm were impregnated with DDA and EM and were thoroughly dispersed into the epoxy used as the matrix and applied on steel. Fourier-transform infrared spectroscopy (FTIR) analysis confirms the presence of DDA loaded nanotubes and the loading of inhibitor was estimated by thermogravimetric analysis. Additionally, the amount of the released corrosion inhibitor was identified by gas chromatography–mass spectrometry (GC–MS). The scanning electron microscopy (SEM), analysis shows the polymer healing of the prepared coatings when damaged. The electrochemical studies indicate that the corrosion rate of the steel samples coated with the epoxy modified with the healing additives decreases after 5 days of immersion in saline water. Unlabelled Image • Smart coatings are developed by mixing DDA-encapsulated nanocontainers in an epoxy matrix. • The encapsulated inhibitor can self-release in response to the change in pH of the medium. • The encapsulated epoxy monomer has the ability to self-heal the scratched coatings. • The developed smart coatings can effectively protect the coated steel surface from corrosion for longer period of immersion. [ABSTRACT FROM AUTHOR]

Crumpled MoS 2 nanosheets were synthesized directly on carbon fiber paper (CFP) through hydrothermal procedure. Molybdenum sulfide precursor was first produced in the solution and then introduced into the autoclave. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirmed the uniform growth of crumpled nanosheets on the CFP that were assigned to MoS 2 according to X-ray photo electron spectroscopy (XPS) and Raman spectroscopy results. Electrochemical measurements of the as deposited MoS 2 crumpled nanosheets performed in 1 M Na 2 SO 4 evidenced a specific capacitance of 249 F g −1 at 2 A g −1 and the good rate capability by retaining 41.3% of initial capacitance at 10 A g −1 . Electrochemical Impedance spectroscopy measurements showed very low charge transfer resistance and very short relaxation time accounting for the pseudocapacitive rectangular cyclic voltammetry (CV) and high rate capability. [ABSTRACT FROM AUTHOR]

In the present work, electrochemically reduced-graphene oxide/cobalt oxide composites for charge storage electrodes were prepared by a one-step pulsed electrodeposition route on stainless steel current collectors and after that submitted to a thermal treatment at 200 °C. A detailed physico-chemical characterization was performed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Raman spectroscopy. The electrochemical response of the composite electrodes was studied by cyclic voltammetry and charge-discharge curves and related to the morphological and phase composition changes induced by the thermal treatment. The results revealed that the composites were promising materials for charge storage electrodes for application in redox supercapacitors, attaining specific capacitances around 430 F g −1 at 1 A g −1 and presenting long-term cycling stability. [ABSTRACT FROM AUTHOR]

Mg alloys are very susceptible to corrosion in physiological media. This behaviour limits its widespread use in biomedical applications as bioresorbable implants, but it can be controlled by applying protective coatings. On one hand, coatings must delay and control the degradation process of the bare alloy and, on the other hand, they must be functional and biocompatible. In this study a biocompatible polycaprolactone (PCL) coating was functionalised with nano hydroxyapatite (HA) particles for enhanced biocompatibility and with an antibiotic, cephalexin, for anti-bacterial purposes and applied on the AZ31 alloy. The chemical composition and the surface morphology of the coated samples, before and after the corrosion tests, were studied by scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDX) and Raman. The results showed that the presence of additives induced the formation of agglomerates and defects in the coating that resulted in the formation of pores during immersion in Hanks' solution. The corrosion resistance of the coated samples was studied in Hank's solution by electrochemical impedance spectroscopy (EIS). The results evidenced that all the coatings can provide corrosion protection of the bare alloy. However, in the presence of the additives, corrosion protection decreased. The wetting behaviour of the coating was evaluated by the static contact angle method and it was found that the presence of both hydroxyapatite and cephalexin increased the hydrophilic behaviour of the surface. The results showed that it is possible to tailor a composite coating that can store an antibiotic and nano hydroxyapatite particles, while allowing to control the in-vitro corrosion degradation of the bioresorbable Mg alloy AZ31. [ABSTRACT FROM AUTHOR]

Abstract: Organically modified silicate (ORMOSIL)–epoxy coatings were formed on aluminium alloy 2024-T3 in order to protect the substrates from corrosion. Organic and inorganic compounds, all known for their corrosion inhibition ability, were incorporated into the polymer matrix for the improvement of the corrosion resistance. The ORMOSIL–epoxy coatings were deposited via the dip-coating process. The properties of the coatings were investigated after 24h of curing at 90°C. The morphology of the coatings was examined by scanning electron microscopy (SEM). Their composition and structure were investigated by Fourier transform infrared spectroscopy (FT-IR) and energy dispersive X-ray analysis (EDX). The corrosion resistance of these coatings was investigated using electrochemical impedance spectroscopy (EIS). The results showed that the most effective corrosion protection ability was provided by the inorganic inhibitors and that an important role can be attributed to the cation in the nitrate salt. [Copyright &y& Elsevier]

Abstract: Nowadays, stainless steel reinforcements appear as an effective solution to increase the durability of reinforced concrete structures exposed to very aggressive environments. AISI 304 is widely used for this purpose. Although the improved durability of reinforcing AISI 304, when compared to carbon steel, there is a high probability of pitting susceptibility in the presence of chlorides. Thus, the present work aims at studying the passivation and passivation breakdown of AISI 304 in alkaline solutions of different pH (pH from 13 to 9), simulating the interstitial concrete electrolyte. These solutions were contaminated with different concentrations of chloride ions (3% and 10%, as NaCl). The electrochemical behaviour was evaluated by d.c. potentiodynamic polarization and by electrochemical impedance spectroscopy (EIS). The morphological features and the changes observed in the surface composition were evaluated by Scanning Electron Microscopy (SEM) together with EDS chemical analysis. The results evidence that pH plays an important role in the evolution of the film resistance and charge transfer processes. Moreover, the effect is highly dependent upon the chloride content and immersion time. [Copyright &y& Elsevier]

Abstract: In this work, the corrosion behaviour of magnesium alloys ZK31, EZ33 and WE54 was studied in sodium borate buffer solution at pH 9.2. The electrochemical processes were studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The composition and morphology of the alloys and corrosion products formed were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The experimental findings highlighted the differences in the corrosion mechanisms of the different alloys tested. The results showed that the presence of rare-earth elements (RE) only increases the corrosion resistance when present in solid solution, as is the case of the WE54 alloy. At pH 9.2, an amorphous yttrium oxide/hydroxide thick film was formed, which possesses greater stability when compared to magnesium oxide/hydroxide. The role of RE in the corrosion mechanism was discussed. [Copyright &y& Elsevier]

Abstract: The inhibiting effect of several organic compounds on the corrosion of 2024 aluminium alloy in neutral chloride solution was investigated in the present work. The candidates were selected based on the assumption that effective inhibitors should form highly insoluble complexes with components of AA2024. Along with organic complexing agents, the salts of rare-earth elements were included into screening electrochemical impedance spectroscopy (EIS) test for getting comparative data. Results of EIS analysis revealed three most effective organic inhibitors: salicylaldoxime, 8-hydroxyquinoline and quinaldic acid. Their anti-corrosion performance was additionally investigated via dc polarization, as well as localized techniques: scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy coupled with scanning Kelvin probe (SKPFM). Localized measurements at exactly the same microdimensional zones of the alloy before and after immersion into 0.05M sodium chloride solution allowed tracing the evolution of the Volta potential, chemical composition, surface topography and formation of corrosion products on the surface and intermetallic inclusions during the corrosion tests. The results show that the quinaldic acid, salicylaldoxime and 8-hydroxyquinoline provide anti-corrosion protection for AA2024 forming a thin organic layer of insoluble complexes on the surface of the alloy. Inhibiting action is the consequence of suppression of dissolution of Mg, Al and Cu from the corrosion active intermetallic zones. [Copyright &y& Elsevier]

Abstract: The present work aims at evaluating the ability of cerium and lanthanum conversion pre-treatments applied on galvanized rebars to hinder the cathodic process of hydrogen release during the early stages of contact between the rebar and the high alkaline environment of the concrete pores solution. The electrochemical behaviour was assessed by polarization resistance, open circuit potential and scanning vibrating electrode technique (SVET). The chemical composition and the morphology of the pre-treated surfaces were evaluated by X-ray photoelectron spectroscopy and scanning electron microscopy. The substrates were immersed in solutions simulating the concrete interstitial electrolyte. The pH was 13.2. For these conditions, the results showed that conversion pre-treatments based on cerium or lanthanum nitrate did not hinder hydrogen evolution, but they changed the corrosion processes occurring on the galvanized rebar during the early stages of immersion. [Copyright &y& Elsevier]

• PEO and a combination of sol-gel and PEO layers were used to mitigate galvanic corrosion between AZ31 and CFRP. • Physico-chemical analysis, SVET and OCP measurements were used to study the galvanic coupling effects. • CFRP accelerated corrosion of AZ31 when the galvanic couple was formed. • The morphology of the PEO layers reduced the barrier protection effect. • Combination of an intermediate sol-gel coating and a PEO layer slowed down the corrosion activity in the AZ31/CFRP composite. This work investigates the influence of different barrier layers, based on plasma electrolytic oxidation (PEO) and PEO/sol-gel, on the galvanic corrosion between carbon fiber reinforced polymer (CFRP) and the magnesium alloy AZ31. The scanning vibrating electrode technique (SVET) and open circuit potential (OCP) monitoring were combined with microscopic observations using scanning electron microscopy (SEM) to study the galvanic corrosion phenomena at the interface between the Mg AZ31 alloy and the CFRP layers. The PEO and sol-gel layers serving as barrier between AZ31 and CFRP were able to slow down the galvanic corrosion activity providing short-term corrosion protection. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) is successfully electrodeposited from a graphene oxide-containing suspension under stirring and no sonication onto Ni foam by applying −1.5 V/SCE. The electrodeposited material is characterized by X-Ray Diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, Fourier Transform Infra-Red spectroscopy (FTIR) and Thermogravimetric analysis (TGA). FTIR and TGA results indicate the formation of hydrogenated rGO after electrodeposition. In addition, the electrochemical response of the rGO/Ni electrode is evaluated by cyclic voltammetry in 1 M potassium hydroxide solution. The results reveal that the electrode possesses higher conductivity and lower polarization loss compared to bare Ni foam, opening wider perspectives to design composites with improved electrochemical performance. Unlabelled Image • Direct electrodeposition of hydrogenated reduced graphene oxide (rGO) onto Ni foam. • rGO is electrodeposited under stirring and no sonication. • A facile, one-step, fast and environmentally friendly route to electrodeposit rGO • Enhanced electrochemical performance in KOH solution [ABSTRACT FROM AUTHOR]