Multi-scale study on the electrochemical behavior and corrosion mechanism of 5083 aluminum alloy with different microstructures in a NaCl environment

Ma M., Liu G., Yang Z., Zhang G.

Xia J., Zhu G., Gao X., Wang S., Chang Z., Guo N., Ding J., Zhai X., Li X.

In this paper, activation (H7 series), over-passivation (H6 series), and passivation states were presented in the electrochemical processes. 304-Cu stainless steel was treated with two electrolytes (H6, H7), and then passivated by air oxidation, citric acid pickling, or ultraviolet irradiation. The variations of voltage and surface energy described the different stages of the process, corresponding to the changes in morphology, and the evolution of the passivation film. The H6 series with flat surfaces had higher corrosion potential and pitting corrosion potential, and the corrosion current was lower. The H7 series with rough surfaces had a thicker passivation film, poorer pitting corrosion resistance, and the best general corrosion resistance. The formula derived from the Arrhenius equation illustrates the functional relationship between the surface energy and the resistance of the passivation film, and the results validated the conclusions.

Yu T., Wang S., Liu X., Liu S., Shi C., Du N.

7075 Al alloy is strengthened by ultrasonic surface rolling process (USRP), and the process parameters are changed to regulate the microstructure. The thickness, grain size and distribution of different strengthening layer are characterized in detail by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The influence of different strengthening structures on their electrochemical corrosion behavior are studied using scanning Kelvin probe (SKP) and electrochemical impedance spectroscopy (EIS). The results show that the average grain size of untreated Al alloy is 2.89 μm, the surface SKP potential is low and fluctuates greatly, and has high sensitivity to pitting corrosion. After USRP treatment, the surface roughness of 7075 Al alloy decreases, the grain size is significantly refined and shows a gradient distribution, SKP potential in the strengthening area increases and becomes more stable, the passive film on the surface thickens, the density of pits significantly decreases, and the corrosion resistance is improved. Besides, the samples with thicker plastic deformation layer and surface nanocrystallization (average size of 39.9 nm) exhibit better performance compared to other samples.

Yuan C., Li J., Zhou X.

For the AgCuOIn2O3SnO2 electrical contact composites, the interfacial bonding state and microstructure of each oxide with the silver matrix are still unknown, and in order to elucidate the interfacial state between Ag and CuO, first-principles calculations based on density-functional theory are used to establish the low-exponential surfaces of Ag and CuO, respectively, and to perform convergence tests. The computational results show that the Ag (111) surface and the CuO(100)-CuO surface are the most stable surfaces among the respective low-exponential surfaces, and thus the Ag (111) surface and the CuO(100)-CuO surface are selected to constitute the interfacial model, and the atomic structure, the adhesion work, and the interfacial energies of the interfaces are systematically analyzed. The calculation results show that the Ag (111)/CuO(100)-CuO interface has metallic properties and still has strong electrical conductivity, when the interface spacing d0 = 3.0 Å, the interfacial adsorption work is the largest, and the value of the interfacial energy is the lowest and positive, which indicates that the Ag (111)/CuO(100)-CuO interface exists stably thermodynamically, and the interfacial stability is relatively good. Moreover, the Ag/CuO interface is bonded by ionic bonding and partial covalent bonding, the interface is well bonded, and the O atoms play a more critical role in the interfacial bonding, and the accuracy of the calculated results is verified by experiments.

Pu C., Li C., Miao Y., Lu Q., Peng J., Xu Z., Zhang X., Yi J.

The electrochemical corrosion behaviour and corrosion mechanism of Sn-9Zn-xGe alloy in 3.5 wt.% NaCl solution was investigated using electrochemical techniques combined with surface characterization techniques. The results showed that the alloy corrosion was mainly affected by the rupture of passivation film and Cl- migration along grain boundaries. Trace Germanium (Ge) addition refined the microstructure and improved the corrosion potential of the alloy. Solder alloys containing 0.6 wt.% Ge formed a uniform and dense passivation film on the corrosion surfaces, which reduced the corrosion rate and increased the corrosion resistance.

Jin H., Sui Y., Yu X., Feng J., Jiang Y., Wang Q., Sun W.

In this paper, a quantitative method to evaluate the degree of differences in corrosive behavior of different crystallographic-oriented planes of Al and Al alloys in 3.5 wt% NaCl solution is provided. The corrosion potential Ucorr, corrosion current density Icorr and electrochemical corrosion rate of (1 0 0), (1 1 0) and (1 1 1) ideal surfaces and corresponding surfaces with vacancy and chloride ion adsorption considerations in single-crystal aluminum were derived by first principles calculation. The results show that the corrosion potential and corrosive current density increases in the order of U(110)corr

Nkoua C., Esvan J., Tribollet B., Basseguy R., Blanc C.

A combined electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) approach showed that the corrosion behaviour of 5083 Al alloy was controlled by Mg dissolution at the Mg-rich intermetallic coarse particles (IMCs) that were defects of the passive film. It was thus shown that microstructures with high amount of Mg-rich IMCs were less resistant to corrosion. EIS experimental data were well superimposed with fitted ones calculated using a model proposed in the literature for pure magnesium. The model allowed to plot the resistivity profiles of the passive films, which highlighted their double-layer structure evidenced by XPS.

Xie T., Yang Y., Wang J., Ying T., Xu Z., Zeng X.

The adsorption energy of F, H on the titanium surface with 46 doping elements was calculated in the first-principles approach. Compared with Ti in fuel cell environment, the adsorption energy would decrease with the doping of C, N, etc., while increasing with Be, Mg, etc. doping. The increase of adsorption energy will improve corrosion resistance, and testified by the previous research, so as to provide guidance for the design of corrosion-resistant Ti alloy bipolar plates.

Aydın F.

The necessity to reduce fuel consumption and gas emissions has revealed the need to use materials with high specific strength. Aluminium (Al) matrix composites are widely used in aerospace, automotive and defence industries due to their low density, high strength and good wear resistance. Knowing the effect of reinforcement materials on the corrosion performance of Al matrix composites is essential for estimating service life. This review focuses on the recent corrosion studies of Al matrix composites. Researchers have performed different corrosion tests such as potentiodynamic, electrochemical impedance spectroscopy, immersion and salt spray to explore the corrosion rate. The effect of the reinforcement type and content on the corrosion performance of the Al matrix composites is reviewed. This review also explains the reasons for the increase/decrease in corrosion resistance and damage mechanisms.

Wang R., Zhu Q., Zuo Y., Cheng L., Wang J.

Amrhar O., Lee H., Lgaz H., Berisha A., Ebenso E.E., Cho Y.

Metal oxides are gaining momentum rapidly for application in water pollutant remediation. In this study, the adsorption proprieties of two anionic dyes, i.e., acid yellow 36 (AY36) and acid orange 6 (AO6) on the (1 1 0) surface of rutile titanium dioxide (TiO2) in an aqueous medium were investigated using computational methods. The density functional theory (DFT) was used to determine the reactivity of organic molecules by calculating the frontier molecular orbital energies, energy gap (ΔEgap), chemical hardness (η), chemical softness (σ), electronegativity (χ), chemical potential (μ), electrophilicity (ω), the fraction of electrons transferred (ΔN), back-donation energy (ΔEback-donation), Mulliken charge, and Fukui indices. The obtained results showed that the AY36 molecule is more reactive than the AO6 molecule and may have a good adsorption capability compared to the AO6 dye. The most favorable adsorption configurations of AY36 and AO6 molecules were investigated using molecular dynamics (MD) simulation. The calculated interaction energies by MD simulation showed that the TiO2 (1 1 0) surface has a high sensitivity to interact with the two anionic dyes, with more affinity toward the AY36 molecule. Furthermore, to get deep insights into the chemistry of interactions between the anionic dyes and the TiO2 (1 1 0) surface, the self-consistent charge density functional tight-binding (SCC-DFTB) method was carried out. Results showed that anionic dyes adsorbed on the TiO2 (1 1 0) surface by forming covalent bonds between oxygen atoms of the sulfonic group and Ti atoms. Theoretical insights from this work would serve as a guide for researchers to explore the application of oxides in water pollutant remediation.

Ji Y., Hu Q., Xia D., Luo J.

The corrosion characteristics of passive films on 1060, 2024 and 5083 aluminum alloys formed in citric acid solution are studied in Cl–-containing solutions by combining scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The passive film on 1060 pure Al exhibits the best corrosion resistance while the presence of alloying elements (Cu and Mg) in the passive films reduce the corrosion resistance of the passive films on 2024 and 5083 Al alloys. According to first-principles calculations, Cu/Mg doping γ-Al2O3 surfaces are looser and more reactive than pure γ-Al2O3 (110) surface, and Cl adsorption behavior is changed in Cu/Mg doping γ-Al2O3 surfaces. This illuminates the difference of corrosion resistances of 1060, 2024 and 5083 aluminum alloys from the aspects of the passive film structure and interaction of chlorine ions with the passive films.

Xia D., Ji Y., Zhang R., Mao Y., Behnamian Y., Hu W., Birbilis N.

Localized corrosion of the aluminium alloy AA5083-H111 in a simulated dynamic seawater/air interfacial zone and a full seawater immersion zone was investigated with electrochemical impedance spectroscopy and electrochemical noise. Al-Fe/Ti intermetallic particles (IMPs) on localized corrosion were examined with focused ion beam, transmission electron microscopy and energy dispersive x-ray spectroscopy. As compared with the full immersion zone, the interfacial zone showed higher oxide film resistance and charge transfer resistance, which was attributed to the high oxygen flux in that zone. Localized corrosion arose from IMPs that posessed an Al-Fe phase and a Ti enriched phase.

Guo X., Zhou J., Zhang Y., Zhang X., Ren J., Lu X.

In this paper, the adsorption behavior of Na atom on T-carbon (111) surface is investigated in detail by first principles calculations. The adsorption of Na atom on the T-carbon (111) surface is a chemical adsorption with excellent stability. The minor opening of the bandgap is present. The charges transfer from Na atom to C atom, which leads to a transition of the bonding properties from covalence to ionicity. For the H-site adsorption system, the adsorption energy is the lowest, indicating that the system is the most stable. At the same time, C-Na has the lowest bond population, indicating its strong ionic property. Additionally, the dielectric loss of the adsorbed system reduces, especially for the H-site adsorption, which is conducive to the improvement of the service life in electron material devices. In absorption spectrum, the peak values decrease and shift to the lower energy direction, resulting in the appearance of redshift phenomenon. The reflection peak and energy loss values are greatly reduced, in which the trend is most obvious for the H-site adsorption. The above analysis results provide a theoretical basis for the application of photosensitive devices and open a window on the design and control the micro-nano devices.

Dun-Bo T., Hong Z., Cui-Hong H., Yu-Rong X., Zhen L., Ri-Qiang Z., Xiao C.

Abstract Electrochemical corrosion behavior of Sn-containing Al–Zn–Mg aluminum alloy has been studied in detail. The localized corrosion behaviors were studied by electrochemical impedance spectroscopy (EIS) analysis, and the potentiodynamic polarization measurements. The grain structure, grain-boundary microstructure, grain-boundary microchemistry, pitting and intergranular corrosion morphology were characterized and observed using SEM, EDS, TEM, SAED and HRTEM analyses. Based on these tests, the effects of grain-boundary on the corrosion resistance in our Sn-containing Al–Zn–Mg alloys before/after bake hardening were analyzed systematically. Finally, the relationship between chemical composition, microstructure evolution and corrosion behaviour was revealed. The results indicate that the bake hardening process improves the corrosion resistance compared to the pre-aging state. The grain size has little effect on the electrochemical corrosion bahavior.