In this study, the localized corrosion susceptibility of AA2050‐T84, AA2198‐T851, and AA2024‐T3 alloys was compared by immersion in three test solutions, specifically sodium chloride solution (3.5% ...NaCl), EXCO solution, according to ASTM G34‐18, and a solution for intergranular corrosion (IGC) test recommended by ASTM G110‐15 and via scanning vibrating electrode technique (SVET). The results showed higher susceptibility of AA2050‐T84 alloy to all types of corrosion tested compared to the other studied 2XXX series alloys. Corrosion penetration was deeper in the AA2050‐T84 due to its microstructural characteristics as a difference in the micrometric Cu‐Rich intermetallic particle distribution on the surface and related to the distribution of the T1 (Al 2 CuLi) phase.
•AA2198-T851 is a potential substitute for AA2524-T3 with higher pitting resistance.•AA7081-T73511 is more prone to pitting corrosion than the AA7050-T7451.•Cathodic Al7Cu2Fe particles promote ...dissolution of adjacent 7XXX matrix.
The 2XXX and 7XXX series aluminium alloys are commonly used in aircraft applications where high strength-to-weight ratios are required. The present study aims to compare the corrosion resistance of two novel alloys developed for aircraft industry (AA2198-T851 and 7081-T73511) to that presented by the alternative base alloys (AA2524-T3 and 7050-T7451, respectively). Results indicate that AA2198-T851 may show a superior corrosion performance compared to AA2524-T3, being a potential candidate for its replacement, due to best mechanical properties. In what concerns the 7081-T73511, its resistance to pitting corrosion may be lower than for the base line alloy 7050-T7451.
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•A simple one-step preparation of inhibitor-loaded mesoporous SiO2 nanocontainers was designed.•The new one-step method was efficient, energy-saving and organic solvents-free compared ...with traditional multi-step preparations.•The resultant nanocontainers had high uptake of inhibitor (∼16 wt.%) and possessed pH-responsive inhibitor release property.•The coating incorporated with the nanocontainers significantly improved the corrosion resistance of copper substrate.
We present a simple one-step method of preparing inhibitor-loaded mesoporous silica nanocontainers without extra steps such as template removal or inhibitors loading. The synthetic method is based on the high solubility of organic inhibitors in hydrophobic cores of template micelles. The resultant inhibitor (benzotriazole) and cetyltrimethyl ammonium bromide (CTAB) co-loaded silica nanocontainers had high uptake of inhibitor (∼16 wt.%) and possessed H+ ion-responsive inhibitor release property. When examined by scanning vibrating electrode technique, the coating doped with these nanocontainers exhibits effective corrosion protection property. These results suggest that the one-step synthetic method was efficient, energy-saving and organic solvents-free among others.
Microscopic aspects of electrochemical reactions in a B10 Cu-Ni alloy/2205 duplex stainless steel (DSS) galvanic couple immersed in NaCl solution were investigated by electrochemical noise (EN) ...technique, scanning kelvin probe force microscopy (SKPFM), scanning vibrating electrode technology (SVET) as well as by scanning electron microscopy (SEM) method. Wavelet analysis by EN technique and microscopic characterization showed that the galvanic corrosion process can be divided into five detail stages. SKPFM and SEM observations revealed that the B10 Cu-Ni alloy/2205 DSS is a small-scale B10/ferrite/austenitic galvanic corrosion system that reduces the resistance of 2205 DSS to pitting attack.
•Galvanic corrosion of Cu-Ni alloy/2205 DSS couple was analyzed.•Pitting corrosion was observed on the surface of cathodic 2205 DSS in the galvanic system.•The galvanic corrosion process can be divided into five stages by wavelet analysis.•More accurate corrosion mechanism can be revealed by EN analysis.
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•Propolis is an efficient green corrosion inhibitor for bronze surface.•The inhibitive effectiveness of propolis on bronze is time-dependent.•The main organic constituents of propolis ...sample were identified by HPLC-DAD.•The adsorption of propolis on bronze surface obeys Langmuir isotherm.
In the present work, the inhibitive action of natural propolis on bronze corrosion in a weakly acidic solution containing Na2SO4 and NaHCO3 at pH 5 was evaluated using multiscale electrochemical techniques, namely potentiodynamic polarization, electrochemical impedance spectroscopy and scanning vibrating electrode technique measurements. The major constituents of propolis were identified by HPLC. Surface characterization was performed by SEM-EDX and AFM analysis. Experiments were performed as a function of the propolis concentration and immersion time in the corrosive electrolyte. The obtained results showed that propolis presents good anticorrosive properties on bronze, acting as a mixed-type inhibitor, but its protective effectiveness is time-dependent. The highest inhibiting efficiency of 98.9% was obtained in the presence of 100ppm propolis, after about 12h of exposure to inhibitor-containing electrolyte through the stabilization of Cu2O on the bronze surface. The inhibitive properties of propolis on bronze corrosion are likely due to the adsorption of its main constituents (flavonoids and phenolic compounds), through the oxygen atoms in their functional groups and aromatic rings, which have been evidenced by FT-IR spectra. The adsorption of propolis on bronze was found to follow Langmuir adsorption isotherm.
Laser-cleaned surface of hot-rolled AA7024-T4 alloy exhibited higher corrosion resistance in 3.5 wt.% NaCl solution than the as-received, due to the removal of the original less protective oxide ...layer consisting of MgO and MgAl2O4 and formation of more protective oxide layer containing Al2O3 and MgO.
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•Laser cleaning removed the original oxide layer comprising of MgO+MgAl2O4.•Laser cleaning induced a formation of oxide layer consisting of Al2O3+MgO.•Laser-cleaned surface exhibited higher corrosion resistance than the as-received.•Newly formed oxide film by laser cleaning offered better protection against corrosion.
Laser cleaning has been considered as a promising technique for the preparation of aluminium alloy surfaces prior to joining and welding and has been practically used in the automotive industry. The process is based on laser ablation to remove surface contaminations and aluminium oxides. However the change of surface chemistry and oxide status may affect corrosion behaviour of aluminium alloys. Until now, no work has been reported on the corrosion characteristics of laser cleaned metallic surfaces. In this study, we investigated the corrosion behaviour of laser-cleaned AA7024-T4 aluminium alloy using potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The results showed that the laser-cleaned surface exhibited higher corrosion resistance in 3.5 wt.% NaCl solution than as-received hot-rolled alloy, with significant increase in impedance and decrease in capacitance, while SVET revealed that the active anodic points appeared on the as-received surface were not presented on the laser-cleaned surfaces. Such corrosion behaviours were correlated to the change of surface oxide status measured by glow discharge optical emission spectrometry (GDOES) and X-ray photoelectron spectroscopy (XPS). It was suggested that the removal of the original less protective oxide layer consisting of MgO and MgAl2O4 on the as-received surfaces and the newly formed more protective oxide layer containing mainly Al2O3 and MgO by laser cleaning were responsible for the improvement of the corrosion performance.
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•Reactive sputtering was shown advantageous for producing Nb2O5 thin film.•Nb2O5 coating improved the corrosion resistance of the 2524-T3 alloy.•Nb2O5 coating improved the wear ...resistance of the 2524-T3 alloy.
This study focuses on the surface modification of 2524-T3 Al alloy substrates, highly prospective in aeronautical sector, by niobium oxide films employing reactive sputtering technique. A set of Nb2O5 thin films was obtained and characterized by various techniques including AFM, SEM, EDX, FTIR and XPS. After the morphological and structural characterization of the thin films, electrochemical and micro-abrasive wear tests were performed. The results of FTIR are not conclusive regarding the possible valences in the chemical structure of the thin film, such as Nb2O5 or NbO2, whereas XPS results only indicate the presence of Nb2O5. The EIS spectra indicate that both the bare alloy and the Nb2O5 covered material were suffering pitting corrosion, although the obtained parameters indicate that the coating is expected to increase the corrosion resistance of the material, reducing the severity of the pitting attack. Localised tests demonstrated that Nb2O5 coating was able to delay the onset of corrosion process and significantly improve corrosion resistance of alloy 2524-T3 Al alloy. The 2524-T3 Al alloy containing the Nb2O5 coating presented greater wear resistance than bare material, with reduction in the wear rate, under a mixed wear mode by rolling and scratching in both materials.
The inherent porous structure of PEO coatings is regarded as a drawback for long-term protection. In this investigation, the presence of pores and defects in the PEO coating was exploited as ...reservoirs for corrosion inhibitors to generate self-healing properties on AA2024. Smart coating systems were fabricated on the PEO layer in which 8-hydroxyquinoline (8-HQ) and benzotriazole (BTA) were employed as corrosion inhibitive layers followed by a sol-gel sealing. The protective performance relies on the mechanical interlocking between the sol-gel coating and the sublayer plus the sealing ability of the sol-gel in the presence of the intermediate layer.
•The synergistic inhibitive behavior in 0.1 M NaCl was found for 8-HQ and BTA with a ratio of 7/3.•The impregnation of the PEO layer by inhibitors reduced its porosity.•The optimal concentration to form the inhibitive layer was 5 g/L.•Mechanical interlocking and self-healing properties in the PEO/intermediate/sol-gel coating system were evidenced.•High corrosion protection performance was obtained for the optimized system till five weeks of immersion in 0.1 M NaCl.
•SVET shows the galvanic corrosion for an aluminium/copper model in NaCl solutions.•SVET depicts the inhibitive actions of benzotriazole and cerium chloride.•Benzotriazole rapidly reacts with copper ...surfaces, but inhibition is non-persistent.•Cerium ions react with the hydroxyl ions, blocking the copper surface after 46h.•A synergistic inhibitive effect is achieved by combining benzotriazole and cerium salt.
An aluminium/copper galvanic coupling model suitable for Scanning Vibrating Electrode Technique (SVET) analysis was elaborated with the aim of simulating a galvanic couple characteristic of AA 2024. The inhibitive effects brought by benzotriazole (BTA) and cerium chloride (CeCl3) on the Al/Cu model were evaluated, separately and combined, in neutral aerated sodium chloride solutions. A positive synergistic effect was revealed yielding permanent corrosion protection for 46h of immersion. Complementary techniques such as UV spectrophotometry and ToF-SIMS were employed, respectively, to investigate the decomposition of BTA molecules and to confirm the chemical composition of a combined BTA-based/Cerium-based layer.
In this work the protective effect of layered double hydroxide (LDH) films directly grown on the surface of 2024-T3 aluminium alloy is investigated using electrochemical impedance spectroscopy (EIS) ...and the scanning vibrating electrode technique (SVET). The SVET results focused on the localised nature of the corrosion process and are in agreement with the global response measured by EIS. Furthermore, the evolution of active corrosion protection rendered by LDH films is surveyed at microscale for the first time for long immersion periods in NaCl solution and in the presence of induced defects. The quantitative information provided by SVET is discussed and a parameter to describe the degree of corrosion localisation is introduced based on LDH systems.
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