Corrosion Protection Of AA2024-T3 Research Articles

Combined influence of Ce(III) and iodide ions for corrosion protection of AA 2024-T3 in acidic to neutral chloride-rich environments: Electrochemical and surface characterization studies

It has been reported that trivalent cerium salts are effective inhibitors for corrosion of AA2024-T3 in neutral to alkaline corrosive environments, but poor in acidic environments. In this study, work was done for extending corrosion resistance provided by Ce(NO3)3 to acidic pHs as low as 2.5 through the addition of iodide ions. To this end, potentiodynamic polarization was used to ascertain the optimum Ce(III) concentration for the inhibition of AA2024-T3 corrosion in 3.5%NaCl solution. This optimum concentration is found to be in a range between 0.1 and 0.3 mmol/L Ce(III). This optimum concentration also gives a maximum width of the passive region under the pitting potential (Epit). Based on this optimization, further work was performed as a function of pH without and in the presence of 0.01 mol/L KI at five pH values (2.5, 4, 5, 7, and 8). Without iodide the best inhibition provided by the Ce(III) cation is at pH = 7 but active corrosion is observed at pH = 2.5 with an estimated inhibitor efficiency (−37.6%). The addition of iodide ions (I–) reverses the poor corrosion resistance whereby the inhibitor efficiency becomes 47.7%. Moreover, at pH = 4 the efficiency is also increased from 54.0% to 81.0% with iodide addition providing a significant improvement over Ce(III) cations alone under acidic conditions. There is a synergistic effect between I– anion and Ce(III) cation, which is determined to be 2.4 and 2.1 at pH = 2.5 and 4.0, respectively. At pH=5 and 7 there is virtually no change in inhibition but at pH = 8 the inhibition falls away due to a considerable amount of cerium precipitating out of solution as cerium carbonate. The protective film formed on sites in the aluminium alloy surface at different pH values was examined by both scanning electron microscopy with energy dispersive X-ray analysis and X-ray photoelectron spectroscopy to determine the role of these ions as a function of pH in surface inhibition. It is proposed that at pH = 2.5 protection is provided by a bilayer adsorption of iodide with “capping” cerium ions, but at pH = 4 protection occurs through precipitate formation on active cathodes thereby shutting down the oxygen reduction reaction.

Corrosion Protection of AA2024-T3 by Cerium Malate and Cerium Malate-Doped Sol–Gel Coatings

Cerium malate (CeMal) was tested as a corrosion inhibitor for AA2024-T3 in this work. Corrosion inhibition on bare AA2024-T3 indicated that the inhibiting effect was a result of the synergistic effect of cerium cations and maleic anions. The corrosion of AA2024-T3 was stagnated by greatly reducing the corrosion current when CeMal was present in NaCl solutions. CeMal was adsorbed on the surface of AA2024-T3 forming a protective film in the initial stage. Then, cerium cations transformed to cerium oxide/hydroxides, precipitating on the cathode sites to inhibit the further corrosion. The electrochemical impedance spectra results of the sol–gel coatings proved that CeMal was an effective corrosion inhibitor in the sol–gel coatings to provide corrosion protection for AA2024-T3.

Corrosion protection of AA2024-T3 by sol-gel film modified with graphene oxide

Graphene oxide (GO) was introduced into sol-gel systems to enhance the corrosion protective properties of the obtained film on AA2024-T3 aluminum alloy. The characterization of morphology, microstructure and component of the films indicated that GO covalently reacted with silanol groups from hydrolyzed 3-glycidoxypropyl-trimethoxysilane (GPTMS) monomer, forming silane functionalized GO (SGO) by COSi covalent bonds. Corrosion protective properties of the films were evaluated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and immersion tests studies. The results showed that the addition of GO improved the corrosion protective properties of sol-gel film distinctly by providing the good barrier property of layered GO and enhancing the cross-linking density of the film. The significant improvement of GO on sol-gel film mainly focused on the resistance and capacitance of film itself. The optimal concentration of GO addition was 0.5 mg mL−1, at which the film was uniform and showed good corrosion protective properties in 0.05 M NaCl aqueous solution. The corrosion current density of the sol-gel film with 0.5 mg mL−1 GO was one order magnitude smaller than that of sol-gel film without GO. The protection efficiency of the film was up to 99.45%.

Corrosion protection of AA2024-T3 by LDH conversion films. Analysis of SVET results

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.

The role of Ce(III)-enriched zeolites on the corrosion protection of AA2024-T3

The present work demonstrates that the addition of Ce-enriched zeolite microparticles to hybrid sol–gel formulation confers protection to the coating. After two weeks of immersion the integrity of sol–gel film remains unchanged. These properties are due to the fact that the Ce(III) loaded zeolite microparticles are released in response to the adsorption of ionic species involved in the corrosion process of AA2024-T3 substrate. Zeolite adsorption of Cu2+ cations from intermetallic dissolution and Cl− anions from the solution is shown to take place, enhancing the protective properties of the coating. The microparticles and coatings characterization were carried out by SEM/EDS and the protection properties of the modified coatings were assessed using EIS and localised electrochemical impedance spectroscopy (LEIS) measurements.

Corrosion protection of aluminium alloy 2024-T3 in 0.05 M NaCl by cerium cinnamate

The corrosion protection of AA 2024-T3 in 0.05 M NaCl by cerium cinnamate has been studied. Polarization measurements demonstrate that cerium cinnamate is markedly effective for suppressing anodic process of the alloy corrosion during the initial 72 h of immersion. The protection mechanism during the immersion period appears to involve two stages: the deposition of cerium cinnamate, and then hydrolysis of cerium ions forming a cerium oxide/hydroxide, prevailing over the foregoing deposition. This study also elucidates the inhibition effect of cerium cinnamate on the early corrosion attack occurred from the second phase particles by X-ray photoelectron spectroscopy and electron-probe microanalysis.

Corrosion protection of AA2024-T3 using rare earth diphenyl phosphates

Existing corrosion protection technologies for aluminium alloys utilising chromates are environmentally damaging and extremely toxic. This paper presents a preliminary investigation into rare earth diphenyl phosphates as new environmentally benign corrosion inhibitors. Full immersion weight loss experiments, cyclic potentiodynamic polarisation measurements and Raman spectroscopy were used in this study. Results show cerium diphenyl phosphate (Ce(dpp) 3) acts as a cathodic inhibitor, decreasing cathodic current density and E corr by passivating cathodic intermetallic particles on the alloy surface. Mischmetal diphenyl phosphate (Mm(dpp) 3) acts a mixed inhibitor, shifting E corr to more noble values, decreasing cathodic current density, increasing the breakdown potential and suppressing pitting.

Corrosion Protection of AA2024-T3 by Metavanadates and Vanadium-Based Conversion Coatings

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Corrosion protection of AA 2024-T3 by bis-[3-(triethoxysilyl)propyl]tetrasulfide in sodium chloride solution.: Part 2: mechanism for corrosion protection

The corrosion protection of AA 2024-T3 by films of bis-[3-(triethoxysilyl)propyl]tetrasulfide (bis-sulfur silane) was studied in a neutral 0.6 M NaCl solution using potential transient, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results showed that a highly crosslinked or dense interfacial layer that developed between the silane film and the aluminum oxide is the major contribution to the corrosion protection of AA 2024-T3. The formation of this interfacial layer heavily restricts pit growth underneath via retarding the transport of corrosion products, as well as effectively blocks a number of cathodic sites available for cathodic reactions.