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•Al graded Mg-Al thin films were synthesized via combinatorial magnetron sputtering.•Al graded Mg-Al thin films were analyzed via in-situ electrochemistry.•The Mg-Al solid solution ...corrosion resistance increases with the Al concentration.•Exceeding cAl ∼ 4 wt% causes a distinct anodic current density decrease.•Exceeding cAl ∼ 4 wt% causes a predominant cathodic partial reaction on the surface.
The effect of varying Al concentrations on the electrochemical corrosion resistance of binary Mg-Al solid solutions thin films under alkaline immersion conditions was investigated via a combination of in-situ flow-cell, scanning vibrating electrode technique and microscopy analysis. These spatially resolving characterization techniques are employed along the Al concentration gradient of the combinatorically grown thin films enabling efficient screening of the Al concentration dependent electrochemical corrosion behaviour. The analysis revealed an increasing corrosion resistance with increasing Al concentration, as a consequence of Al induced hydroxide reinforcement. Specifically, the addition of >4 wt.% Al decreases the corrosion current density in the range of 70–90 % compared to pure Mg.
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•An eco-friendly drug losartan potassium (LP) is developed as a superior mixed-type inhibitor for steel corrosion.•The multi-anchored film of LP is formed on steel ...substrate.•Theoretical modelling provides deep insights into the inhibition performance of LP.
The present study aimed to find a suitable alternative for traditional and hazardous corrosion inhibitors. A green antihypertensive drug-Losartan potassium (LP) with superior corrosion protection ability was developed for the first time. Gravimetric method, potentiodynamic polarization, AC impedance, and scanning vibrating electrode technique (SVET) were combined to evaluate the corresponding inhibition performance towards Q235 steel in HCl medium. The results indicated that LP exhibited superior mixed-type corrosion protection to steel at different temperatures owing to the formation of compact and ordered LP-adsorption film on steel surface. Specifically, the inhibition performance values increased to 88.9%, 91.8%, and 92.0% for 5 mM LP at 298, 308, and 318 K, respectively. Meanwhile, N-Fe bond from X-ray photoelectronic spectroscopy (XPS) implied multiple anchoring interaction between steel and LP with nitrogen atoms as active sites. Based on DFT calculation and molecular dynamics (MD) simulation, the obtained low energy gap (ΔE) and high Ebinding values as well as radial distribution function (RDF) analysis represented strong chemisorption of LP on Fe substrate, which theoretically explained the favorable inhibition effectiveness of LP compound at molecular or atomic level.
•Sealing ability of different sol-gel coatings for the PEO layer on AA2024.•Electrochemical evaluation of the duplex coatings via SVET and EIS techniques.•The crucial role of compactness, ...hydrophobicity, and impregnation for the sol-gel sealing.•PSG-ZT illustrated the best sol-gel sealing for the PEO layer.•Insufficient sealing and hydrophilic properties of the PSG-AP for the PEO coating.
Owing to the inherent porosity of the coatings produced through the PEO process, the application of sol-gel coatings as a post-treatment has drawn immense attention thanks to their eco-friendly and reliable protective characteristics. Various parameters affect their performance, and the type of sol-gel precursors plays a significant role. In this study, various sol-gel precursors were used to prepare four types of PEO/sol-gel coating systems followed by an investigation of their sealing ability and corrosion resistance properties on AA2024 alloy. The corrosion prevention performance of the coatings was studied by electrochemical impedance spectroscopy (EIS) along with Scanning Vibrating Electrode Technique (SVET) analyzes. Some chemical characterization tests, such as Fourier Transform Infrared Spectroscopy (FT-IR) and rheology measurement, affirmed the influence of the sol-gel chemical composition on its compactness and the network viscosity. The distinctive sealing ability of different sol-gel coatings for the defects and pore filling of the PEO layer was visualized by Scanning Electron Microscope (SEM). To this end, different sol-gel formulations and various sol-gel network properties accordingly caused dissimilar sealing features for the PEO pores and, subsequently, the corrosion resistance of the duplex PEO/sol-gel coating is widely dependent on the used sol-gel precursors.
High toxicity is the main reason to limit the application of traditional corrosion inhibitors. Herein, the development of a green and high-efficiency alternative to displace traditional and hazardous ...corrosion inhibitor is an urgent task. Cauliflower extract (CFE) has the potential ability to solve this problem because it comes from nature and also contains plenty of heterocyclic organics. Therefore, CFE, as an eco-friendly corrosion inhibitor, was prepared for the first time via a simple and green extraction method. The typical electrochemistry and scanning vibrating electrode technology (SVET) tests prove that CFE can effectively inhibit the copper corrosion in 0.5 M H2SO4. What's more, this inhibition effect is still strong when prolonging the immersion time, and the highest inhibition efficiency reaches up to 99% at 48 h. Based on the surface composition analysis result, it can be obtained that CFE protective film is formed on the copper substrate, and thereby significantly block the active corrosion sites of copper. Furthermore, the parallel adsorption state and high Ebinding value from MD simulation imply the powerful interaction between CFE molecules and Cu, which is crucial evidence to explain the inhibition effect of CFE for copper at the molecular level.
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•A green cauliflower extract (CFE) as corrosion inhibitor was prepared via a green and simple extraction method.•The high and sustainable anti-corrosion ability of CFE for copper was achieved.•Strong adsorption happened between CFE molecules and copper surface.•The anti-corrosion mechanism of copper with CFE was explained in detail.
In this work, a polyethyleneimine-grafted graphene oxide (PEI-GO) hybrid material was prepared as an effective filler to improve the anticorrosion performance of waterborne epoxy coating. The ...successful covalent reaction between PEI and GO was confirmed by FTIR, Raman, XPS, XRD and TGA measurement. The epoxy coating filled with modified and unmodified graphene oxide was characterized by SEM and Raman spectroscopy. The results showed that PEI-GO was uniformly dispersed in the epoxy matrix. It was found that the PEI-GO hybrid materials displayed considerable superiorities in improving corrosion resistance of epoxy coating by EIS and SVET. Besides, the optimal content (0.25 wt%) of PEI-GO was obtained through experimental results. Moreover, the desirable anticorrosive property of PEI-GO/EP composite coating is proposed to be mainly attributed to the role of PEI, which fully stimulated the barrier properties of graphene oxide by improving its dispersion in the epoxy coating and also enhanced the crosslink density of epoxy resin by increasing the surface activity of the graphene oxide to the epoxy groups.
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•Polyethylenimine (PEI) was grafted on graphene oxide (GO) surface.•The PEI-GO hybrid improved the compatibility between GO and epoxy resin (EP).•The PEI-GO/EP composite coating had longer service life and better anti-corrosion property.•The presence of PEI-GO hybrid increased the density of epoxy coating and suppressed the corrosion of metal substrate.
The influence of variations in pH and time on the bimetallic corrosion of π-Al8Mg3FeSi6 phase and pure aluminum in acidic, neutral and basic solutions has been evaluated by potentiodynamic ...polarization and scanning vibrating electrode technique (SVET) in combination with Energy dispersive X-ray spectroscopy (EDX). The bimetallic corrosion of π-Al8Mg3FeSi6/Al couple was found to depend on time and pH. Polarization tests show that at pH 2 (acidic) and pH 6 (near-neutral), the π- phase functions as the anode while Al functioned as the cathode, whereas the opposite was observed at pH 13 (basic). SVET scans show that in pH 2 and 13 solutions, cathodic fluxes emerge from π- phase, and the anodic fluxes develop from Al. Whereas in pH 6 solution, self-dissolution of π- phase occurs and both cathodic anodic processes develop on the π- phase with no conspicuous electrochemical activity on Al. The rigor of the bimetallic coupling of π- phase and Al was more pronounced at pH 2 and 13 and the order of the intensity of the galvanic effect is pH 13 > pH 2 > pH 6. EDX surface analysis indicates preferential discharge of more electropositive elements in π-Al8Mg3FeSi6 phase in solution. In acidic and neutral environments selective dissolution of Mg/Al in π- phase the occurs, in near neutral solutions selective dissolution of Mg occurs, in alkaline environments selective dissolution of Al occurs; these lead to the enrichment of more noble elements which have a direct impact on the galvanic polarity of the π-Al8Mg3FeSi6 in the long term.
•Cu2O under AM1.5 illumination can promote the corrosion of Cu matrix.•The photoinduced corrosion of Cu aroused by Cu2O is detected by SVET.•A method for in-situ determining the photoinduced current ...is proposed.
The electrochemical associated with photoelectrochemical behaviors of Cu electrodeposited with Cu2O layer were investigated in this work. The corrosion of Cu was promoted due to the enhanced anodic and cathodic processes under AM 1.5illumination compared with that in the darkness, especially for the anodic process. The photoinduced corrosion of Cu by Cu2O was detected by Scanning Vibrating Electro Technique (SVET). The effect of Cu2O on the promotion of Cu corrosion under illumination can be ascribed to the narrowed depletion layer in Cu2O under illumination, which facilitates the separation of hole-electron pairs. The resultant holes give rise to the oxidation of the Cu matrix and lead to a promoted corrosion consequently. Besides, a method for in-situ determining the photoinduced current of a semiconductor material is proposed.
•Corrosion of Q235 carbon steel in 1 M HCl solution is inhibited significantly by NCDs (p-CDs and o-CDs).•The inhibition efficiency is strongly dependent on the concentration of NCDs.•The adsorption ...of NCDs involves both chemisorption and physisorption.
Nitrogen doped carbon dots (NCDs) were synthesized and used for inhibiting the corrosion of Q235 carbon steel in hydrochloric acid (HCl) solution. Inhibition effectiveness in short- and long-term immersion was examined using electrochemical measurements, weight loss and surface analysis. Results revealed the inhibition efficiency was improved significantly after adding NCDs and strongly dependent on the concentration of NCDs. SVET results showed that the sample immersed in HCl solution with NCDs showed lower anodic current density mapping than that in blank HCl solution. According to the data extracted from the Langmuir adsorption, the absorption of NCDs involved both chemisorption and physisorption.
•Microstructure and electrochemical activities of dissimilar AA2050 and AA7050 aluminum alloys.•The friction stir welding (FSW) of the dissimilar alloys affected the microstructure and the ...electrochemical behavior of the different regions investigated.•Galvanic interactions between the coupled welded zones were visualized by SVET and SIET analyses.•Spatially-resolved images of anodic and cathodic sites associated to corrosive attack, evolution of hydrogen and local pH changes were obtained and studied.
In this work, the effects of friction stir welding (FSW) on the microstructure and electrochemical activities of dissimilar AA2050 and AA7050 aluminum alloys have been investigated. Local electrochemical tests supported by surface analytical characterization were used to study the local electrochemical activities developed along the weld zones of the dissimilar alloys. The investigation was carried out on the cross-section of the welded Al alloys. The results showed that the friction stir welding (FSW) of the dissimilar alloys affected the microstructure and the electrochemical behavior of the different regions (HAZ, TMAZ, SZ) formed by the welding process. Scanning vibrating electrode technique (SVET) and micropotentiometry by using an ion-selective microelectrode showed that TMAZ was the zone with the highest electrochemical activity. This zone corresponded to the transition region between the two welded alloys. The high electrochemical activity observed in this region was associated with the effect of welding on the microstructure and, also, with the galvanic coupling between the two alloys, where the alloy AA7050 acted as an anode and the AA2050 as a cathode. Preferential corrosion attack on the AA7050 alloy was also evident.
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