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Corrosion of reinforcing steel in concrete is a worldwide problem. An important factor affecting such process is the concrete composition and, especially the presence of additives. In fact, the kinetics of water absorption and water evaporation are affected both by the environment conditions and by the nature of the additives. This is important for powdered additives, which can partially occlude the porous structure, changing porosity and permeability of concrete too. Reinforced concrete samples were modified by adding spent fluid cracking catalyst powders (SFCC) and an environment friendly commercial inhibitor. The samples were submitted to consecutive cycles of 15 day of immersion (in saturated NaCl electrolyte) followed by 15 day of drying. Samples were regularly monitored by electrochemical Impedance Spectroscopy (EIS). The results revealed that the additives interfere with the water adsorption/evaporation kinetics in concrete, a process resulting from the joint effect of diffusion and capillary processes. These interferences occur due to three combined mechanisms: two related to pore blocking and pozzolanic activity, which are the result of structural changes in concrete and affect the diffusion processes/mechanism; the third one is the capillary mechanism, which is strongly dependent from the chemical nature of the additives, but can also be influenced by structure modifications. This mechanism can increase, reduce or eliminate the capillary processes. [ABSTRACT FROM AUTHOR]

A silane-based coating modified with titanium IV iso-propoxide was developed to slow down the corrosion rate of AZ31 and ZE41 magnesium alloys intended as biodegradable implants materials. Electrochemical impedance spectroscopy (EIS) was used to monitor the corrosion evolution over 7 weeks in simulated body fluid at 37 °C. A homogeneous crack-free 3 μm-thick coating provided corrosion protection for 2 and 3 weeks to the ZE41 and the AZ31, respectively. The corrosion mechanisms and the nature of the corrosion products of the coated systems are discussed and correlated to the coating morphology before and after the immersion tests. [ABSTRACT FROM AUTHOR]

Coatings tailored to corrosion protection of metallic substrates are of the utmost relevance to ensure reliability and long-term performance of coated parts as well as the product value of the coated materials. Presently, there is a strong emphasis on the development of advanced functional and smart coatings for corrosion protection in different technological applications. On the one hand, there is a need for more advanced coatings for conventional applications and, on the other hand, there is a need to answer the requirements of several new Hi-Tech applications. Thus, this review highlights the most recent trends in the field of functional coatings for corrosion protection of metallic materials in a wide range of technical applications. Emphasis is given to self-healing coatings and smart coatings combining multiple functionalities for increased corrosion protection. Recent developments on the introduction of functionalities based on encapsulation of corrosion inhibitors, anti-fouling agents and superhydrophobic additives or modification of organic and hybrid matrices via chemical manipulation are reviewed. Special attention is dedicated to functional coatings for corrosion protection of bioresorbable metallic implants that have an important impact in biomedical applications. [ABSTRACT FROM AUTHOR]

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: Nowadays, there is a strong demand on the search of thinner, but more effective organic coatings for corrosion protection of metallic substrates, like galvanised steel, used in the automotive industry. In order to guarantee effective corrosion protection of these coatings, and because chromate-based pigments cannot be used, one of the most attractive strategies consists on the modification of the organic matrix with nano-additives filled with corrosion inhibitors, which can be released to the active sites. In this work, two different nano-additives are explored as potential self-healing materials for the development of active protective coatings. These additives are layered double hydroxides and cerium molybdate hollow nanospheres loaded with mercaptobenzothiazole, as a corrosion inhibitor. These additives were added to epoxy primers, individually, or combining the two nanoadditives in the same layer. The electrochemical behaviour and the potential of self-healing ability were studied by electrochemical impedance spectroscopy, scanning vibrating electrode technique and scanning ion-selective electrode technique. The results reveal that both types of nanocontainers can provide effective corrosion inhibition on artificial induced defects, at different stages of the degradation process. Moreover, the results also show that there is a synergistic effect concerning corrosion inhibition and self-healing potential when a mixture of the two nanocontainers is used. The mechanism of self healing is presented and discussed in terms of effect of organic inhibitor and role of the nanocontainers, including effect of cerium ions released from cerium molibdate nanoparticles. [Copyright &y& Elsevier]

Abstract: The present work aims at understanding the role of CeO2 nanoparticles (with and without activation in cerium(III) solutions) used as fillers for hybrid silane coatings applied on galvanized steel substrates. The work reports the improved corrosion protection performance of the modified silane films and discusses the chemistry of the cerium-activated nanoparticles, the mechanisms involved in the formation of the surface coatings and its corrosion inhibition ability. The anti-corrosion performance was investigated using electrochemical impedance spectroscopy (EIS), the scanning vibrating electrode technique (SVET) and d.c. potentiodynamic polarization. The chemical composition of silanised nanoparticles and the chemical changes of the silane solutions due to the presence of additives were studied using X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance spectroscopy (NMR), respectively. The NMR and XPS data revealed that the modified silane solutions and respective coatings have enhanced cross-linking and that silane–cerium bonds are likely to occur. Electrochemical impedance spectroscopy showed that the modified coatings have improved barrier properties and the SVET measurements highlight the corrosion inhibition effect of ceria nanoparticles activated with Ce(III) ions. Potentiodynamic polarization curves demonstrate an enhanced passive domain for zinc, in the presence of nanoparticles, in solutions simulating the cathodic environment. [Copyright &y& Elsevier]

Abstract: The present work investigates the corrosion behaviour of AZ31 Magnesium alloy (Mg AZ31) substrates pre-treated with a water soluble bis-aminosilane modified with multiwall carbon nanotubes (CNTs). Prior addition to the silane solution, the CNTs were submitted to a treatment in an aqueous solution containing cerium nitrate or lanthanum nitrate. The chemical composition of the treated CNTs and of the modified silane coatings was assessed by X-ray Photoelectron spectroscopy (XPS). The thickness and the morphology of the silane coatings were investigated by scanning electron microscopy (FEG/SEM). The pre-treatment of the Mg AZ31 was performed by dipping the metallic coupons in the silane solution modified with the CNTs. The electrochemical behaviour of the silane coated coupons was studied during immersion in 0.05 M NaCl solutions, using the scanning vibrating electrode technique. The electrochemical investigation showed that the activation of the CNTs with the rare-earth salt delays the corrosion activity of the Mg AZ31 substrates. The analytical and microscopic study suggested that the CNTs are homogeneously dispersed in the silane coating and that the CNTs act as support for inhibitor storage. [Copyright &y& Elsevier]

Abstract: This work aims to develop and study new anticorrosion films for AZ31B magnesium alloy based on the sol–gel coating approach. Hybrid organic–inorganic sols were synthesized by copolymerization of epoxy-siloxane and titanium or zirconium alkoxides. Tris(trimethylsilyl) phosphate was also used as additive to confer additional corrosion protection to magnesium-based alloy. A sol–gel coating, about 5-μm thick, shows good adhesion to the metal substrate and prevents corrosion attack in 0.005M NaCl solution for 2 weeks. The sol–gel coating system doped with tris(trimethylsilyl)-phosphate revealed improved corrosion protection of the magnesium alloy due to formation of hydrolytically stable Mg–O–P chemical bonds. The structure and the thickness of the sol–gel film were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The corrosion behaviour of AZ31B substrates pre-treated with the sol–gel derived hybrid coatings was tested by electrochemical impedance spectroscopy (EIS). The chemical composition of the silylphosphate-containing sol–gel film at different depths was investigated by X-ray photoelectron spectroscopy (XPS) with depth profiling. [Copyright &y& Elsevier]

Abstract: In situ monitoring of the chloride content is one of the most important procedures in preventing and controlling chloride-induced corrosion in reinforced concrete structures. Thus, the development of chloride sensors is of paramount importance for the continuous monitoring of concrete structures. The sensors must present long lifetime and reliability and operate in a wide range of chloride concentrations. The present work aims at developing and testing a sensor based on Ag/AgCl electrodes for in situ monitoring of chloride ions in reinforced concrete structures. Although these electrodes are widely used in analytical experiments due to their sensitivity to the chloride ion, little is known on their behaviour during exposure to alkaline environments, such as those existing in concrete. The multiprobe sensor presented in this work was tested in mortar and concrete specimens, revealing good stability. The results reveal that the Ag/AgCl sensor presents good sensitivity in a wide range of chloride concentrations. [Copyright &y& Elsevier]

One of the most important causes for reinforcing steel corrosion is the presence of chloride ions. They cause localised breakdown of the passive film that initially forms on steel as a result of the alkaline nature of the pore solution in concrete. The harmful chloride ions can be originated from the use of contaminated mix constituents or from the surrounding environment. The determination of a critical level, above which serious problems can occur, has been one of the main goals of investigation. Unfortunately, it is difficult to establish such a value since the chloride level is influenced by several factors. Thus, after concrete contamination, it is of fundamental importance to follow the activity of chlorides and the state of the reinforcing rebars. In this respect, the use of electrochemical techniques such as polarisation resistance, electrochemical impedance, galvanostatic pulse and potential measurements have shown to be powerful tools. Nevertheless, the interpretation of the results becomes sometimes a difficult task. A large number of authors have dedicated several studies to the interpretation of such measurements and a highly dispersed number of interpretations can be found in literature. The aim of this paper is to present an overview on the state-of-the-art of the most important aspects of the corrosion process initiated by chlorides, its development and monitoring techniques. [Copyright &y& Elsevier]

The deposition of γ-glycidoxypropyltrimethoxysilane (γ-GPTMS) film onto AA2024-T3 aluminum alloy surface was performed via two techniques: dip-coating and electrodeposition. The electrodeposited coatings were performed under potentiostatic control at different cathodic potentials (namely −0.80, −1.30 and −1.70 V vs.SCE). γ-GPTMS films were characterized by physical, microscopic and spectroscopic techniques: Pull-off test, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) and X-Ray Photoelectron Spectroscopy (XPS). The electrochemical behaviors of coatings were assessed in chloride solution by means of Electrochemical Impedance Spectroscopy (EIS). The synthesis conditions have shown a key role in the morphology and the anticorrosion performance of γ-GPTMS coating. Results revealed the uneven nature of the dip-coated film that resulted in a non-satisfactory anticorrosion performance. For the electrodeposited coatings, the protectiveness was dictated by the imposed potential value. The film electrogenerated at −0.80 V vs.SCE possessed the best protective performance. Moreover, it was found to be uniform, compact and proved superior adhesion strength when compared to the dip-coated film. [ABSTRACT FROM AUTHOR]

Abstract: Corrosion protection of aluminium alloys often relies on the application of a coating on the metallic surface. The coating normally combines a barrier effect that restricts the ingress of corrosive species, with an inhibitive role induced by corrosion inhibitor pigments added to the coating formulation. However, the direct addition of corrosion inhibitors to the coating can cause some detrimental interactions between components, as well as formation of preferential electrolyte pathways, compromising the barrier properties. Moreover, electrolyte uptake and ageing may result in leaching of those corrosion inhibitors. In order to extend the corrosion inhibition ability of organic coatings one possible solution is to store the inhibitors inside nano or microreservoirs compatible with the coating matrix and able to sense the local changes induced by the corrosion process. This strategy has led to the development of a new generation of “smart” coatings for anti-corrosion purposes. The aim of this work is to study the anti-corrosion properties of water-based epoxy coatings loaded with pH sensitive particles, acting as feedback active containers for corrosion inhibitors and applied on the aluminium alloy AA2024-T3. For this purpose micron size calcium carbonate beads were modified with different corrosion inhibitors: cerium nitrate, salicylaldoxime and 2,5-dimercapto-1,3,4-thiadiazolate. These particles act as pH sensitive reservoirs because they dissolve at acidic pH, releasing the corrosion inhibitor, which then suppresses the corrosion activity of the bare metal. Electrochemical impedance spectroscopy (EIS) was used to estimate the electrical parameters assigned to the barrier properties of the coating and corrosion inhibition ability in the presence of inhibitor loaded calcium carbonate beads. The most relevant corrosion inhibition effects were observed from CaCO3 microbeads modified with cerium ions. The self healing potential of this new system was corroborated by localised electrochemical impedance measurements (LEIS). [Copyright &y& Elsevier]

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]

Abstract: This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic–inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic–inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor, which seemed to be due to the formation of a more uniform and densely reticulated siloxane-PMMA film. [Copyright &y& Elsevier]

Abstract: This work aims at studying the corrosion behaviour of AA2024-T3 pre-treated with bis-[triethoxysilylpropyl]tetrasulphide. Simultaneously, the work investigates the influence of the Cu-rich intermetallic particles on the formation of the silane film. The analytical characterisation of the silane films was performed by Auger electron spectroscopy and X-ray photoelectron spectroscopy. The corrosion performance of the pre-treated substrates was evaluated by electrochemical impedance spectroscopy. Atomic force microscopy associated with Kelvin probe was also used to determine the influence of the silane film on the Volta potential distribution on the alloy surface. The results show that copper present in the intermetallics plays an important role on the film formation. [Copyright &y& Elsevier]

• Crambe oil-polyurethane derived organic coatings applied on ASTM 1200 Al alloy. • Tannin in solution increased the corrosion potential and decreased the corrosion current. • The best coating plus tannin protected Al alloy for up to 30 days in 3.5% NaCl solution. This work aims at investigating the effect of tannin, a natural compound, as corrosion inhibitor for bare and coated aluminum alloys (AA1200). Tannin was characterized by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR) and its interaction with the sample surface was evaluated by computational calculations using the density functional theory (DFT) and electrochemical measurements. The corrosion behavior was studied by open circuit potential (E OCP), electrochemical impedance spectroscopy (EIS) and by the scanning vibrating electrode technique (SVET). Complementary studies were performed by scanning electron microscopy (SEM). Results demonstrated that tannin is an effective corrosion inhibitor protecting both coated and uncoated aluminum samples. [ABSTRACT FROM AUTHOR]

pH-sensitive calcium carbonate microparticles were loaded with polyethyleneimine (PEI), a corrosion inhibitor, and used as anti-corrosion additive in epoxy coatings applied on carbon steel. The presence of PEI in the CaCO 3 particles was confirmed by Fourier-Transform Infra-Red Spectroscopy (FTIR) and the loading was quantified by Thermal Gravimetric Analysis (TGA). The protective performance of the modified coatings applied on carbon steel was investigated by Electrochemical Impedance Spectroscopy (EIS) and the results evidenced that the modified coatings provided high corrosion protection and very stable barrier properties over time. The self-healing ability was investigated by Localized Electrochemical Impedance Spectroscopy (LEIS) and by the Scanning Vibrating Electrode Technique (SVET) on coated samples artificially damaged and immersed in NaCl solutions. The results revealed an important corrosion inhibition effect, stable over time, in the coatings modified with the PEI loaded particles. The corrosion inhibition effect involves the dissolution of the calcium carbonate microparticles in the local acid media formed at the anodic sites and subsequent release of the corrosion inhibitor that forms a protective film on the steel surface. Image 1 • Nanostructured pH sensitive CaCO 3 particles were successfully loaded with Polyethyleneimine (PEI). • Electrochemical impedance spectroscopy demonstrated the high compatibility of the PEI loaded particles with epoxy coatings. • Localized electrochemical tests in presence of defects evidenced corrosion healing ability. [ABSTRACT FROM AUTHOR]

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]

Graphical abstract Highlights • Inhibitive effects of CeCl 3 /triethanolamine on AA2024/graphite couples were revealed. • SVET/SIET tests showed that inhibition mechanisms depend on the electrodes area ratio. • CeCl 3 inhibited localised corrosion of AA2024-T3 (trenching, IGC) coupled to graphite. • Triethanolamine formed complexes with Cu ions when Cu-rich particles were active. Abstract The inhibition mechanism of cerium chloride and triethanolamine on the galvanic corrosion of AA2024-T3/graphite in NaCl electrolyte was investigated by localised electrochemical techniques. Quasi-simultaneous measurements of ionic current densities and pH were performed by the Scanning Vibrating Electrode Technique (SVET) and Scanning Ion-Selective Electrode Technique (SIET). Surfaces were analysed by Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX) and X-Ray Photoelectron Spectroscopy (XPS). This work follows a recent publication (Coelho et al. 2018) and discusses the effect of inhibitors on two AA2024-T3/graphite galvanic couples, constructed with two different areas ratio, evidencing that this parameter significantly influences the corrosion and corrosion inhibition process. [ABSTRACT FROM AUTHOR]

The corrosion mechanism of two AA2024-T3/graphite galvanic couples, with different electrodes area ratio, was studied in 12.00 mM NaCl solution using the Scanning Vibrating Electrode Technique (SVET) and the Scanning Ion-Selective Electrode Technique (SIET). Both techniques were used, quasi-simultaneously, to monitor the current density distribution and the pH associated to the corrosion process occurring in the galvanic couples. The morphological features and the elemental composition of the electrodes' surfaces, after 20 h of immersion, were analysed by Scanning Electron microscopy and Energy Dispersive X-ray Spectroscopy (SEM-EDX). The results show that the area of the electrodes in the galvanic couple significantly influences the corrosion mechanism. For the couple, with the highest AA2024/graphite area ratio (M1), both anodic and cathodic processes developed on the alloy surface, resulting in localised corrosion (trenching of the matrix around intermetallics) at the cathodic zones as detected by SVET and SIET. A more generalised anodic dissolution of AA2024 (corrosion of the matrix and grain boundaries) was observed for the sample with the lowest area ratio (M2), however. [ABSTRACT FROM AUTHOR]

In this work, we report a comparative study of the physicochemical properties, particularly the anticorrosion performance of coatings deposited onto AA2024-T3 surface, namely a mono-layer coating of polyaniline (Pani) and a bi-layer one consisted of an inner Pani layer and an external poly(γ-glycidoxypropyltrimethoxysilane (Poly(γ-GPTMS)) layer (Pani/Poly(γ-GPTMS)). For both coating types, Pani was electrodeposited onto AA2024-T3. Poly(γ-GPTMS) layer was applied by dip-coating onto Pani to form the bi-layer coating. Scanning Electron Microscopy (SEM), Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) and Ultraviolet-Visible spectrophotometry (UV–Vis) proved the successful synthesis of coatings. For Pani/Poly(γ-GPTMS), formation of hydrogen bonds between layers was proved. Poly(γ-GPTMS) layer has filled defects of Pani network, where metallo-siloxane bonds, were established. Pani/Poly(γ-GPTMS) coating revealed better adhesion, water repellency and anticorrosion performance than Pani. Electrochemical Impedance Spectroscopy (EIS) demonstrated that the Poly(γ-GPTMS) layer served as an effective physical barrier top-coat against the penetration of corrosive species through the Pani layer. Poly(γ-GPTMS) improved hence, the anticorrosion performance of coating system for a longer exposure period in chloride medium. [ABSTRACT FROM AUTHOR]

The replacement of chromate-based corrosion inhibitors is a requirement for the aerospace sector. New developments demand additional studies to find synergistic combinations of inhibiting species. This paper discusses the synergistic effect resulting from various corrosion inhibitor mixtures proposed for the corrosion protection of aluminum alloy 2024-T3. The corrosion inhibition efficiency and the synergistic factors were determined for AA2024-T3 coupons immersed in 0.05 M NaCl solutions, containing either a single inhibitor or binary combinations of inhibitors. The following inhibitors were tested: Ce 3 + , 8-hydroxyquinoline (8HQ), salicylaldoxime (SAL), and 2,5-dimercapto-1,3,4-thiadiazolate (DMTD). Electrochemical impedance spectroscopy (EIS) and ATR-FTIR in Kretschmann geometry were used to evaluate the chemical and electrochemical variations during the exposure of bare coupons to inhibitor-containing NaCl solutions. The results allowed calculating the synergistic effect for binary mixtures and the most effective mixtures were those containing 8HQ-SAL and DMTD-8HQ. The synergistic effect was also determined for coated coupons. A water-based epoxy coating was modified with calcium carbonate microparticles, loaded beforehand with single inhibitors or with binary mixtures. EIS measurements were performed in 0.5 M NaCl and the results revealed that the epoxy coatings modified with CaCO 3 microparticles, loaded with inhibitor mixtures, provided enhanced corrosion protection. The most effective corrosion protection was observed for two mixtures: CaCO 3 (8HQ + SAL) and CaCO 3 (Ce + SAL). Interestingly, the results revealed that the synergistic effect on bare AA2024-T3 can be different from the situation where the same inhibitor mixtures are used in smart, anti-corrosive coatings. [ABSTRACT FROM AUTHOR]

Ceria nanoparticles (CNPs) were loaded with a corrosion inhibitor 2-Mercaptobenzothiazole (2-MBT), and used as an anticorrosive pigment. For that, the proposed additive was thoroughly mixed (1 wt%) into a Polyolefin matrix to form a nanocomposite coating that was applied on steel substrates. For comparison, non-modified polyolefin coatings, serving as reference were also prepared. Transmission-electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the presence of the corrosion inhibitor (2-MBT) onto the CNPs. Thermal gravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) techniques confirmed ~40 wt% loading capacity of the CNPs. Electrochemical impedance spectroscopy (EIS) analysis of the coatings demonstrated higher and more durable corrosion protection efficiency of the modified polyolefin nanocomposite coatings compared to the reference coatings. The improved corrosion resistance can be attributed to a synergistic combination of corrosion inhibition due to the release of 2-MBT from CNPs and an effective distribution of the anti-corrosion pigments in the polyolefin matrix. The modified polyolefin nanocomposite coatings also demonstrate enhanced mechanical properties, 15 % higher hardness and 17 % higher erosion resistance compared to the reference coatings, due to a hardening effect conferred by the presence of CNPs loaded with 2-MBT. The improved properties of the modified polyolefin nanocomposite coatings make them attractive for industrial applications to protect steel parts. [Display omitted] • Anticorrosive pigments (CeO 2 -2-MBT) were synthesized. • Coatings were formulated by incorporation of CeO 2 -2-MBT into polyolefin coatings. • Modified polyolefin demonstrated the higher corrosion protection efficiency. • Improved corrosion resistance due to the corrosion inhibition due to the release of 2-MBT. • The hardness increased by 15 %, while 17 % higher erosion resistance was found. [ABSTRACT FROM AUTHOR]

Highlights: [•] Multifunctional coatings were synthesized including pigments. [•] Multifunctional coatings were applied to aluminium alloy 2024-T3. [•] Self-healing properties of the coatings were revealed. [Copyright &y& Elsevier]

Abstract: This work aims at studying the electrochemical behavior, by Electrochemical Impedance Spectroscopy (EIS), of austenitic (AISI 304 and AISI 316) and duplex (SAF 2205 and SAF 2304) stainless steels, when embedded in concrete specimens. Concrete specimens were exposed to chloride containing solutions simulating the aggressive conditions found in sweater environments. Samples were fully immersed and submitted to periodic immersion/emersion cycles. EIS and open circuit potential (OCP) were monitored in a monthly basis. Samples containing carbon steel (C-steel) rebars were also prepared for comparison of the corrosion rates between the different materials. The results showed that the austenitic and duplex SAF 2205 stainless steels were passive for all the testing period, due to the formation of protective oxide layer, with the AISI 316 presenting the higher corrosion resistance value. The EIS results suggest an increase of more than one order of magnitude in the corrosion resistance of the duplex steels and AISI 316 comparatively to C-steel rebars. [Copyright &y& Elsevier]

Abstract: This work aims at studying the response of unsupported concrete media by Electrochemical Impedance Spectroscopy (EIS) and its influence in the results obtained for steel corrosion in reinforced concrete samples. Measurements carried out in full immersed samples correspond to a typical electrolyte media, presenting essentially a resistive behavior. Thus, rebar corrosion, which appears commonly at intermediate frequency region, can be assessed and easily interpreted. For samples in partial dry conditions the spectra show several time-constants distributed across the entire frequency range. In the high frequency region, the time constant is ascribed to dielectric properties of the system. At low frequencies the time constant corresponds to the ionic depletion, while the time constant at intermediate frequencies result from charge separation inside the material bulk, typically of unsupported media. Interpretation of the results obtained by EIS for concrete reinforced steel in partial dry conditions cannot be fully interpreted without considering the dielectric behavior of the system. [Copyright &y& Elsevier]

Abstract: Mg alloys can be used as bioresorsable metallic implants. However, the high corrosion rate of magnesium alloys has limited their biomedical applications. Although Mg ions are essential to the human body, an excess may cause undesirable health effects. Therefore, surface treatments are required to enhance the corrosion resistance of magnesium parts, decreasing its rate to biocompatible levels and allowing its safe application as bioresorbable metallic implants. The application of biocompatible silane coatings is envisaged as a suitable strategy for retarding the corrosion process of magnesium alloys. In the current work, a new glycidoxypropyltrimethoxysilane (GPTMS) based coating was tested on AZ31 magnesium substrates subjected to different surface conditioning procedures before coating deposition. The surface conditioning included a short etching with hydrofluoric acid (HF) or a dc polarisation in alkaline electrolyte. The silane coated samples were immersed in Hank''s solution and the protective performance of the coating was studied through electrochemical impedance spectroscopy (EIS). The EIS data was treated by new equivalent circuit models and the results revealed that the surface conditioning process plays a key role in the effectiveness of the silane coating. The HF treated samples led to the highest impedance values and delayed the coating degradation, compared to the mechanically polished samples or to those submitted to dc polarisation. [Copyright &y& Elsevier]

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: Model weldable primer coatings for galvanized steel were modified with submicron containers loaded with corrosion inhibitors. This procedure aims at introducing a new functionality in the thin coatings self-repair ability. The assessment of this property demands new protocols and new approaches, combining conventional electrochemical methods with electrochemical and analytical techniques of micrometer spatial resolution. Thus, in this work model defects were created in the coatings by using a focused ion beam (FIB). The coated samples, containing the model defects, were immersed in a NaCl 0.05M solution and the corrosion inhibition ability was studied using the scanning vibrating electrode technique (SVET) and the scanning ion-selective electrode technique (SIET). SVET–SIET measurements were performed quasi-simultaneously. Qualitative chemical analysis was performed by SEM combined with EDS. Complementary studies were carried out by electrochemical impedance spectroscopy (EIS) to assess the effect of the containers filled with corrosion inhibitors on the barrier properties of the coatings. The electrochemical results highlight the importance of the combined use of integral and localized electrochemical techniques to extract information for a better understanding of the corrosion processes and corresponding repair of active microscopic defects formed on thin coatings containing inhibitor filled containers. [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 present work reports an innovative approach for surface functionalisation of magnesium alloys (WE54) containing yttrium and rare-earth (RE) elements. A two-step surface modification consisting on the formation of an anodic film followed by the deposition of a hybrid silane layer obtained by dipping in a bis-[triethoxysilylpropyl]tetrasulfide silane (BTESPT) solution was performed on the WE54 alloy. The anodic films were formed by two different ways: (i) a passive film was formed by anodic polarisation of the alloy at 0.5V in NaOH solutions of pH 13 for 24h and (ii) an anodic layer was formed by anodising the substrate for 1h at a potential of 50V in the same solution. The corrosion behaviour was evaluated by electrochemical impedance spectroscopy in 0.005M NaCl solutions for one week. The results show that the two-step treatment improves the corrosion resistance comparatively to the untreated blank substrate. The corrosion resistance of the anodised sample treated with silane is significantly better than the treatment combining passive film and silane. For this system, the overall impedance increases by three orders of magnitude. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the performance of bis-1, 2-(triethoxysilyl) ethane (BTSE) as a pre-treatment to protect the AA 2024-T3 against corrosion has been investigated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves, and the scanning vibrating electrode technique (SVET). The microstructural and morphological characterizations were carried out via scanning electron microscopy and atomic force microscopy and the chemical composition evaluated using contact angle measurements and X-ray photoelectron spectroscopy (XPS). The electrochemical results showed that the additives improved the anticorrosion properties of the coating. The chemical characterization indicated that additives contribute to an increased degree of surface coverage, as well as to a more complete reticulation. The SVET results evidenced the self-healing abilities of Ce ions. [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: 1,12-bis(1,2,4-triazolyl)dodecane (dTC12) is an excellent corrosion inhibitor for carbon steel in deaerated 1 M HCl solution. In this work electrochemical and analytical techniques were used to study the inhibition of corrosion on carbon steel in acidic medium. The carbon steel corrosion inhibition of dTC12 was attributed to the synergistic effect between chloride anion and quaternary ammonium ion. The protective efficiency of the film was higher than 90%, indicating that corrosion of carbon steel in 1 M HCl is reduced by dTC12. The effect of dissolved oxygen on the inhibition efficiency was also investigated. The results show that the inhibition efficiency increases in early stage and decreases for a long immersion time. [Copyright &y& Elsevier]

• Biobased self-healing PU coating with Zn micro-flakes were applied on AA7475. • E OCP values and current density/pH monitoring proved zinc was an anodic inhibitor. • Corrosion protection was better in the presence of 7.5 wt% Zn in the coating. • The self-healing and corrosion inhibition effects were confirmed by SVET/SIET, LEIS. AA7475 is a modern and competitive high strength alloy of relevance to the aerospace industry. In this work biobased organic polyurethane coatings were prepared from vegetable oils (crambe oil and castor oil) without (blank coating) and with incorporation of Zn micro-flakes to impart corrosion inhibition. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR) confirmed the incorporation of zinc in the polymeric matrix and atomic force microscopy (AFM) confirmed the coating homogeneity. The barrier properties of the coatings were studied by electrochemical impedance spectroscopy (EIS) and indicated better corrosion resistance for the sample with the highest content of Zn micro-flakes. Localized electrochemical techniques, namely the scanning vibrating electrode technique (SVET), pH micro-potentiometry (or scanning ion-selective electrode technique - SIET) and localized electrochemical impedance spectroscopy (LEIS) permitted to discriminate the details of the corrosion inhibition process. The results demonstrated that the Zn-containing coatings provide effective corrosion protection of the AA7475 and the protective ability improved significantly in the presence of 7.5 wt% Zn micro-flakes in the coating. [ABSTRACT FROM AUTHOR]

The depreciation of assets and safety threats because of corrosion has forced to develop eco-friendly and smarter corrosion protection strategies. In this study, natural Gum Arabic (GA) was used as a corrosion inhibitor and loaded into cerium oxide nanoparticles (CONPs) to develop an environment-friendly additive for corrosion protection of coated steel in the marine environment. This additive was uniformly dispersed into an epoxy formulation that was used to protect steel plates. Epoxy coatings containing CONPs, without GA, were also prepared as reference. High-Resolution Transmission Electron Microscopy (HR-TEM) and Fourier Transform infrared spectroscopy (FTIR) revealed the successful loading of GA into the CONPs. Thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) techniques confirmed approximately ⁓30.0 wt% loading of GA into the CONPs. Electrochemical impedance spectroscopy (EIS) demonstrated the anticorrosion properties of the epoxy coatings modified with the GA loaded CONPs when compared to reference coatings. The corrosion protection mechanism postulates that GA loaded CONPs act as a filler material for epoxy coating and it can also aid the recovery of the protective properties of the epoxy coating leading to the formation of a stable protective layer. Unlabelled Image • Environmentally friendly Anticorrosive pigments (CeO 2 loaded with Gum Arabic) were added in coating for corrosion protection of steel. • The anti-corrosive pigments were characterized by different techniques and confirmed the loading of Gum Arabic into CeO 2. • Improved anti-corrosion properties of coated samples were evidenced by Electrochemical Impedance Spectroscopy (EIS) techniques. • The Corrosion inhibition mechanism suggests that Gum Arabic delays coating degradation and adsorbs on steel substrate to form a protective layer. [ABSTRACT FROM AUTHOR]

• Efficient corrosion protection of WE43 conferred by Ce(DEHP) 3. • Improved performance of Ce(DEHP) 3 in intact and damaged coatings. • Self-healing of corrosion activity in the presence of Ce(DEHP) 3. • pH-dependant activation of Ce(DEHP) 3. Ce(DEHP) 3 (cerium tri(bis(2-ethylhexyl)phosphate)) is proposed as a self-healing corrosion inhibitor for WE43. The use of Ce(DEHP) 3 in a 3.90 ± 0.54 µm hybrid epoxy-silane coating led to an improvement of the coating barrier properties. The presence of the inhibitor increased the corrosion resistance, and Electrochemical Impedance Spectroscopy tests carried out in 0.5 M NaCl revealed low frequency impedance modulus (0.01 Hz) around 109 Ω∙cm2. The pH-dependant self-healing effect of Ce(DEHP) 3 was evidenced by localized electrochemical techniques, which revealed inhibition of corrosion propagation in artificial defects and decreased net cathodic current densities compared to an unmodified reference coating. Protective behaviour of Ce(DEHP) 3 was related to the combined action of the cerium and organophosphate moieties of this inhibitor, in addition to the protective role of yttrium species derived from the yttrium present in the WE43 magnesium alloy. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Self-healing ability based on hydrogen bonds of biobased coatings applied on aluminum alloy. • SVET/SIET and LEIS confirm the self-healing property of coating with higher polyester content. • Higher flexible segment ratio favors effective corrosion protection and self-healing effect. • Efficient, environmentally, and active protection of aluminum-based surfaces. Biobased polyurethane coatings derived from vegetable oils, with 2 different compositions, were prepared and applied on the AA1200 aluminum alloy to confer corrosion protection. The influence of the ratio between the polyester (flexible segment) and the prepolymer (rigid segment) was investigated. Infrared spectroscopy studies evidenced the difference between the areas of the bands (NH) and optical and scanning electron microscopy evidenced the morphological features of the coating surface before and after immersion in aggressive medium. The barrier properties and anti-corrosion performance of the coatings were evaluated by electrochemical impedance spectroscopy and the results revealed an increase of impedance over the immersion time. Localized corrosion studies confirmed the self-healing effect in coatings formulated with the highest content of polyester. [ABSTRACT FROM AUTHOR]

• CaCO 3 microparticles were loaded with triethanolamine and polyethylenimine as corrosion inhibitors. • The addition of the particles did not damage the barrier properties of epoxy coatings. • Corrosion inhibition confirmed in artificial defects of the coatings modified with the inhibitor loaded CaCO 3 microparticles Calcium carbonate particles were synthesized and loaded with a mixture of two corrosion inhibitors, triethanolamine (TEA) and polyethylenimine (PEI). These particles can serve as pH-sensitive additives in epoxy coatings to provide "smarter" corrosion protection of carbon steel. Electrochemical impedance spectroscopy revealed that calcium carbonate particles loaded with the mixture of corrosion inhibitors improved corrosion resistance of coated panels and did not damage the barrier properties of the coating. Localized electrochemical studies of artificially damaged coatings on steel confirmed the corrosion inhibition effect. [ABSTRACT FROM AUTHOR]

• Polyurethane coatings modified with tannin and applied on AA2024-T3 alloy. • LEIS and SVET/SIET analysis confirm the self-healing property of tannin-modified coatings. • Tannin-modified coating provides effective corrosion protection due to polymer healing. Polyurethane coatings derived from crambe and castor oil formulated with different proportions of additives were modified with tannin and applied on AA2024-T3 coupons. The coatings were characterized by water uptake and attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR). The thickness of the coatings was determined by scanning electron microscopy (SEM) and adhesion was evaluated by the ASTM D3359 standard. The barrier properties and corrosion protection ability were assessed by open circuit potential (E OCP) and electrochemical impedance spectroscopy (EIS). The self-healing ability of the coatings was studied by localized impedance spectroscopy (LEIS) and by the scanning vibrating electrode technique coupled with the scanning ion-selective electrode technique (SVET/SIET). The measurements demonstrate that tannin-modified coatings provide effective corrosion protection due to polymer healing and the results give important highlights concerning the mechanism of corrosion inhibition. [ABSTRACT FROM AUTHOR]

• Urea formaldehyde microcapsules and multilayered microcapsules are synthesized. • Linalyl acetate (self-healing agent) and phenylthiourea (corrosion inhibitor) are used. • Epoxy based smart coatings were developed with these microcapsules. • Structural, thermal and electrochemical properties of coatings are compared. • The multilayered smart coatings demonstrate improved and superior properties. This work reports the synthesis of polyelectrolyte microcapsules and its effect on the anti-corrosion performance of polymeric coating applied on steel substrates. In situ polymerization technique was used for the synthesis of monolayered urea formaldehyde microcapsules loaded with linalyl acetate (MLMCs). These capsules can be broken upon mechanical stress, such as scratches or other forms of mechanical damage. To enhance corrosion protection, Phenylthiourea (PTU), a molecule sensitive to pH, was loaded between consecutive polyelectrolytes layers of polyethylenimine (PEI) and sulfonated polyether ether ketone (SPEEK) build on the surface of MLMCs using the layer by layer technique. This polyelectrolyte layered microcapsules (PMCs) carry linalyl acetate in its core and phenylthiourea entrapped between the outer layers. Both MLMCs and PMCs, in concentration of 6 wt%, were dispersed in the epoxy resin and the resulting formulation was used to coat steel plates. Experimental findings showed that epoxy coatings reinforced with PMCs demonstrate better thermal, self-healing and anti-corrosion properties. This improved performance can be attributed to the release of polymer healing and corrosion inhibiting species from the PMCs. The epoxy coatings modified with PMCs can serve as self healing coating for corrosion protection of steel parts used, for example, in the oil and gas industry. [ABSTRACT FROM AUTHOR]

One of the main applications of SVET in corrosion research is the study of the corrosion inhibition effectiveness and the evaluation of the self-healing effect of inhibitor-containing coatings. The tip of the platinum/iridium vibrating electrode is electroplated with black platinum, which creates a large electrode surface and confers high capacitance to the tip. When studying organic inhibitors in aqueous solutions with SVET, inhibitor adsorption may occur at the tip, causing its contamination and the initial calibration conditions of the system might not be valid. This may lead to an incorrect interpretation of the results. This work is intended to study the effect of different inhibitors (cerium nitrate, 8-hydroxyquinoline, potassium 2,5-dimercapto-1,3,4-thiadiazolate, benzotriazole and mercaptobenzothiazole), typically used for corrosion protection of aluminum alloys, on the Pt probe signal during SVET measurements. The results reveal the detrimental effect of some corrosion inhibitors on the sensitivity of the vibrating probe, an effect that imposes a regular assessment of the electrode state during measurements. The increase of the signal noise was related to a decrease of the probe capacitance, while the false current density signal was a result of the potential drift between vibrating and reference electrodes. [ABSTRACT FROM AUTHOR]

• Novel cerium tri(bis(2-ethylhexyl)phosphate) corrosion inhibition additive. • High compatibility with epoxy coatings. • Increased corrosion resistance of coated steel panels. • Corrosion healing in defects. • Synergistic cathodic and anodic corrosion inhibitors. In this work cerium tri(bis(2-ethylhexyl)phosphate) (Ce(DEHP) 3) particles were used as anti-corrosion pigments in epoxy coatings applied on steel coupons. The composition of the corrosion inhibitor was designed to introduce pH-stimulated corrosion healing in the coating. Electrochemical Impedance measurements demonstrated very high compatibility between the inhibitor and the coating, and effective and stable corrosion protection. Localized electrochemical measurements carried out using the Scanning Vibrating Electrode Technique and Localised Electrochemical Impedance revealed efficient corrosion inhibition of steel exposed in artificially damaged coatings. [ABSTRACT FROM AUTHOR]