Corrosion Behavior Of Aluminum Alloy Research Articles

Corrosion of aluminium alloy AA2024-Τ3 specimens subjected to different artificial ageing heat treatments

The effect of artificial-ageing on corrosion behaviour of aluminium alloy (AA)2024-T3 was investigated. The natural ageing which takes place during the aircraft's lifespan was simulated with isothermal heat-treatments at 190 °C. Electrochemical impedance spectroscopy measurements were performed in different heat-treated specimens to examine the prevailing corrosion mechanisms. Additionally, pre-corroded tensile specimens from different heat-treatment conditions were mechanically tested to assess the corrosion-induced degradation. Different forms of corrosion were revealed in the investigated ageing tempers; intense localized attack was noticed in the initial (T3) and under-aged (UA) tempers. UA condition exhibited the highest susceptibility to corrosion propagation followed by T3, according to the charge transfer resistance RCT and degradation rate of tensile elongation at fracture Af ( ≈ 0.118) and ( ≈ 0.103), respectively. Corrosion-induced degradation rates for the peak-aged (PA) and over-aged (OA) tempers ( ≈ 0.042 and 0.054, respectively) were almost one third of UA, attributed to volume fraction and size of the precipitated second-phase particles.

Experimental and theoretical study on corrosion mechanism of aluminium alloy in different corrosive solutions

A detailed comparison of the corrosion behaviour of Al–O (1 1 1) surfaces on 7A46 aluminium alloy in 1.0 M hydrochloric acid and sulfuric acid solutions was conducted using electrochemical, surface analysis, and density function theory calculations. The results show that the corrosion current density is around 80.62 μA.cm−2 in HCl solution and 104.21 μA.cm−2 in H2SO4 solution. Uncovered defects in the oxide film on the alloy surface can contribute to local erosion and degradation during the corrosion process. In addition, the amounts of charge transferred from the surface of the alloy to Cl− and O2− were 0.811 and 0.178e, respectively, suggesting the formation of an Al–O bond on the surface, which expedites the corrosion process in the HCl solution. In contrast to HCl, the O atoms on the surface of the aluminium alloy obtained 2.032 e and 1.611 e electrons from Al on the Al–O (1 1 1) surfaces and S atoms in H2SO4 solution, respectively, indicating a strong adsorption affinity for SO42−. Both Cl–Al and S–Al bonds form covalent bonds. It is worth mentioning that the resonance peaks in the HCl adsorption system was between −6 eV and 2 eV, whereas that in the H2SO4 adsorption system show a more pronounced shift to the right (−10 eV to 0 eV), suggesting heightened system activity and increased electronic interactions among the atoms in H2SO4 adsorption system. This research contributes to a comprehensive understanding of the surface corrosion behaviour of aluminium alloys, providing valuable insights for the design and application of aluminium alloys across diverse environmental contexts.

How Often Should Microbial Contamination Be Detected in Aircraft Fuel Systems? An Experimental Test of Aluminum Alloy Corrosion Induced by Sulfate-Reducing Bacteria.

Microbial contamination in aircraft fuel-containing systems poses significant threats to flight safety and operational integrity as a result of microbiologically influenced corrosion (MIC). Regular monitoring for microbial contamination in these fuel systems is essential for mitigating MIC risks. However, the frequency of monitoring remains a challenge due to the complex environmental conditions encountered in fuel systems. To investigate the impact of environmental variables such as water content, oxygen levels, and temperature on the MIC of aluminum alloy in aircraft fuel systems, orthogonal experiments with various combinations of these variables were conducted in the presence of sulfate-reducing bacteria. Among these variables, water content in the fuel oil demonstrated the most substantial influence on the corrosion rate of aluminum alloys, surpassing the effects of oxygen and temperature. Notably, the corrosion rate of aluminum alloys was the highest in an environment characterized by a 1:1 water/oil ratio, 0% oxygen, and a temperature of 35 °C. Within this challenging environment, conducive to accelerated corrosion, changes in the corrosion behavior of aluminum alloys over time were analyzed to identify the time point at which MIC intensified. Observations revealed a marked increase in the depth and width of corrosion pits, as well as in the corrosion weight-loss rate, starting from the 7th day. These findings offer valuable insights for determining the optimal frequency of microbial contamination detection in aircraft fuel systems.

Effect of combined microbial and stress corrosion on 7075 aluminum alloy in high salinity environment

The study investigates the impact of the combination of Gram-positive bacteria Bacillus subtilis (B. subtilis) and tensile stress on the surface corrosion of 7075 aluminum alloy (AA7075) in a high-salt solution environment. The change in PH value caused by the growth curve of bacteria was analyzed for corrosion factors. Scanning electron microscopy (SEM) and ultra-depth 3D microscopy (DOF) were used to compare the surface morphology, elements and corrosion of the samples. The presence of a biofilm reduces the corrosion rate by 0.005 ± 0.0004 mm/y and the application of a constant load results in an increase in the corrosion rate to 0.26 ± 0.013 mm/y. The applied stress leads to the disruption of both the biofilm and oxide film on the metal surface, causing a significant reduction in the impedance isolation effect, and resulting in an expansion of the average diameter and depth of the corrosion pit by 372.21 and 29.5 µm, respectively. In electrochemical impedance testing, there is an approximately 7.01×103 Ω increase in impedance value when exposed to B. subtilis environment; conversely, under stress conditions, there is a decrease by 4.02×103 Ω with B. subtilis present. The corrosion current density has increased fourfold to reach 9.15×10−6 (uA/cm2). This suggests that the combination of bacterial and stress can have a complex and detrimental impact on the corrosion behavior of aluminum alloys in high-salt environments.

Improvement of corrosion resistance of 7075 aluminum alloy by ceria coating modified by zinc oxide nanoparticles

Purpose This paper aims to investigate the corrosion resistance of two types of coatings – one is ceria sol coating and the other is ceria sol coating modified by ZnO nanoparticles on 7075 aluminum alloy in 3.5% NaCl solution. Design/methodology/approach Aluminum alloys were dipped into ceria sol and ceria sol modified by ZnO nanoparticles separately and removed after 10 min from the solutions and dried at 110°C for 30 min and heated at 500 °C for 30 min to form the coatings. The coatings have been characterized by using field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The EIS tests were performed in a corrosive solution of 3.5% NaCl. Findings The results showed that the coating of ceria sol modified by ZnO nanoparticles has higher corrosion resistance than the ceria sol coating and the bare sample. Also, the best efficiency is related to aluminum sample immersion after 1 h in NaCl corrosive solution for coating modified by ZnO nanoparticles. Originality/value In this research, the modification of ceria sol coating by ZnO nanoparticles had an effect on improving the corrosion behavior of aluminum alloy. It is also understood that modification of coatings is an effective parameter on corrosion resistance.

New insight into the role of Cu addition on surface nanocrystallization and corrosion behavior of aluminum alloy

Realization of surface-reinforced aluminum alloys with excellent corrosion resistance remains a major topic. Herein, a novel method based on combination of electron beam evaporation plating and surface alloying was proposed. Results revealed that the current density is one order of magnitude less than that of the substrate and that the impedance value is doubled. The nanometer-scale refinement of the grains and the homogenous dispersion of nanocrystallization Al2Cu in the modified layer of aluminum alloy contributed to the enhancement of corrosion resistance. This study is expected to provide a new sight for the development of Cu-reinforced high-performance aluminum alloys.

Corrosion Modeling of Aluminum Alloys: A Brief Review

AbstractCorrosion remains a critical concern in various industries, particularly in applications involving aluminum alloys due to their widespread usage as light structural materials. This work provides a comprehensive overview of the recent advances in modeling techniques for better understanding the corrosion behavior of aluminum alloys. The present study encompasses the state‐of‐the‐art of computational approaches, highlighting their strengths and limitations. Special attention is given to transport models, galvanic couples, localized corrosion, and the incorporation of different factors, such as pH variations, electrolyte thicknesses and dynamic electrolytes into corrosion models. Furthermore, the review delves into both bulk and atmospheric corrosion models. On the other hand, this work also emphasizes a clear differentiation between models designed for bare aluminum alloys and those tailored for coated ones. Additionally, it addresses certain challenges associated with the experimental validation of such models. This review concludes with perspectives on both sophisticated transport models to bridge the gap between industrial and academic investigations, as well as the integration of machine learning and artificial intelligence techniques in corrosion modeling, offering promising directions for future research in this field.

Corrosion Behavior of Aluminum Alloys in Different Alkaline Environments: Effect of Alloying Elements and Anodization Treatments

Aluminum alloys are extensively used to manufacture mechanical components. However, when exposed to alkaline environments, like lubricants, refrigerants, or detergents, they can be corroded, reducing their durability. For this reason, the aim of this study is to investigate the influence of aggressive alkaline solutions (i.e., pH and presence of chlorides) on the corrosion resistance of three aluminum alloys (AA 5083-H111, AA 6082-T6, and AA 7075-T6) with and without anodizing treatments. Open circuit potential (EOCP) and anodic polarization measurements were carried out and typical corrosion parameters such as corrosion current density (icor) and corrosion rate (CR) were determined. Morphology of the corrosion attack and samples microstructure were investigated by scanning electron microscope. Results show that corrosion behavior of the three investigated alloys is influenced by (i) the aggressiveness of the testing environments; (ii) the thickness of the anodizing treatment; (iii) the alloy chemical composition; (iv) the distribution of intermetallic phases in the aluminum matrix. Moreover, three galvanic series have been built also testing other metallic alloys commonly used in mechanical applications, i.e., carbon steel (C40), stainless-steel (AISI 304), and Cu-based alloys (Cu-Ni alloy and CW 617 N, respectively). Results clearly indicate that galvanic series play a fundamental role when it is necessary to select an alloy for a specific environment, highlighting the thermodynamic conditions for corrosion occurrence. On the other hand, kinetic measurements and microstructural studies carried out on the three aluminum alloys stress the importance of the surface treatments and relevant thickness as well as the effect of metal exposure. Future work will involve the study of other surface treatments on aluminum alloys and the evaluation of their corrosion behavior in acidic environments.

Effects of Surfactants on the Corrosion Behavior of Aluminum Alloy in Graphene Nanofluid

In this study, the corrosion behavior of aluminum alloy was investigated in graphene nanoplatelet (GNP) nanofluids prepared with different surfactants. The surfactants include sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), Tween 80, and Gum Arabic (GA). The corrosion properties of the alloy in the different GNP nanofluids were evaluated using potentiodynamic polarization tests at room temperature. The surface morphology of the aluminum alloy was analyzed using a scanning electron microscope coupled with an electron dispersive spectroscopy detector. The experimental results revealed that the addition of surfactants improves the resistance of the aluminum alloy to corrosion in the nanofluid. This was attributed to the adsorption of surfactants on the surface of the alloy to form a protective film layer, which reduces moisture permeability and enhances corrosion inhibition. The addition of GA was found to exhibit the highest inhibition efficiency. This was followed by Tween 80, SDS, and SDBS, which contributes the least inhibition. XRD post-corrosion analysis also reveals the presence of aluminum oxide and aluminum hydroxide phases on the surface of electrodes immersed in all the different GNP nanofluids.

Effect of laser shock peening on the dissolution of precipitates and pitting corrosion of AA6061-T6 with different original surface roughness

The effect of laser shock peening (LSP) on the electrochemical corrosion behavior of AA6061-T6 with different original surface roughness in the 3.5 wt% NaCl solution was investigated by surface morphology measurement, microstructural characterization, and electrochemical corrosion testing. The results show that LSP improves passivation current density by 76.6%− 78.2% and polarization resistance by 287.2%− 288.9%, but does not change the influence law of the surface roughness on the corrosion behavior of aluminum alloy. LSP promoted the complete dissolution of nano-sized Al8Fe2Si particles, generation of ultrafine grains, and local dissolution of micron-sized Al8Fe2Si particles, contributing to the improved corrosion resistance.

Long-time irradiation effect on corrosion behavior of aluminum alloy in pool water of low-power research reactor

This study conducted an evaluation of the corrosion behavior of an aluminum alloy utilized in the Isfahan Miniature Neutron Source Reactor (MNSR). The component analyzed, dry channel (DC), had been exposed to radiation for 12 years in a water environment within the reactor pool since its installation. To determine the effect of radiation on the corrosion of the LT-21 aluminum alloy used in the DC, different parts of the pipe were sampled and various tests were performed. These tests included mechanical strengths (impact, and micro-hardening), XRD, TEM, SEM–EDS, and potentiodynamic polarization (PDP). The parameters measured included corrosion potential, corrosion rate, changes in microscopic structure, and mechanical properties of the aluminum alloy along the entire length of the DC. The neutron and gamma dose distribution along the height of the DC, which was 540 cm, was calculated to determine the correlation between the dose distribution and observed corrosion. The study found that the corrosion mechanisms were complex and resulted from the simultaneous presence of the DC in the pool water and radiation from the reactor core. The observed results are presented and discussed in this study.

Corrosion behavior of 7B04 aluminum alloy under the synergistic effect of Lacticaseibacillus paracasei and Acinetobacter lwoffi

Microbially influenced corrosion (MIC) is a multifaceted phenomenon that is influenced by the synergistic activity of various bacterial species that thrive within biofilms. The present study aims to investigate the impact of interspecies relationships on the corrosion behavior of aluminum alloy (Al alloy). To achieve this, cultures of Lacticaseibacillus paracasei (L. paracasei) and Acinetobacter lwoffi (A. lwoffi) were mixed and analyzed. The electrochemical experimental findings indicated that the 7B04 Al alloy exhibited the lowest Rct value and the highest corrosion current density when immersed in the mixed system. The utilization of surface analysis techniques, such as scanning electron microscopy and stereomicroscope, had led to the discovery of a significant number of corrosion pits in the mixed system. This finding suggested that the corrosion phenomenon was more severe than previously anticipated. The growth curve analysis revealed a synergistic interaction among the mixed bacterial species. The co-cultivation of A. lwoffi and L. paracasei resulted in increased growth activity of L. paracasei in comparison to its growth in a single system. The occurrence of dominant colonies and the development of biofilms were identified as the primary factors contributing to localized corrosion. Furthermore, the combined action of the two bacterial strains exhibited a synergistic effect that exacerbated the corrosion process.

Studies on the corrosion behavior of aluminum alloy in solid/molten salt hydrate phase change material based on fractal theory

The corrosion behavior of Al7075 in the solid and molten states of phase change material were investigated based on fractal theory in conjunction with electrochemical impedance spectroscopy. Results indicated that the surface texture parameters were properly used to describe the corrosion degree as well as identify the different pitting stages. Pitting conformed with Weibull distribution. The statistical parameters Skewness and Kurtosis had a good linear relation with fractal dimension (Ds). Additionally, there was linear relationship between Ds and DEIS based on EIS spectra, due to the fractal geometry of Al7075 electrodes that induced time-constant dispersion and resulted in CPE behaviors.

Development of Reliable Accelerated Corrosion Tests for Aluminum Alloys Used in the Aerospace Industry

Aluminum alloys are not immune to corrosion which can take the form of localized corrosion. Thus, the assessment of the corrosion behavior of aluminum alloys under atmospheric conditions is a major topic for the aerospace industry. One major difficulty in this task is the lack of robust and reliable accelerated corrosion test(s) in this field. Indeed, several tests as the neutral salt spray test (ASTM B117) are used to assess the general corrosion resistance of aluminum, but these tests were not developed specifically for the aerospace industry and are not representative of service conditions. The aim of the present study was to compare the results of various accelerated corrosion test conditions (ASTM B117, VDA 233-102, Volvo STD 423-0014) with newly developed test conditions. Hence, different accelerated corrosion tests were designed by varying several parameters in the Volvo STD 423-0014 such as the salt concentration, time of wetness, and relative humidity. The results obtained on eight aluminum alloys (2xxx, 7xxx, and Al-Li alloys) were then compared to marine exposures. From the results, one test provides the same type of corrosion attacks on the different alloys under atmospheric exposures in the marine site and a good acceleration factor.

Electrochemical corrosion behavior of 6061 Al alloy under high rotating speed submerged friction stir processing

In this study, we report the high rotating speed submerged friction stir processing (HRS-SFSP) designed to modify 6061 Al alloy to improve its corrosion resistance in saltwater. The effect of this processing technology on the microstructure and corrosion behavior of aluminum alloy was studied. The results show that the grain size of Al alloy after HRS-SFSP was refined from 50.8 µm is refined to 3.21 µm. In addition, compared with the low rotation speed (1800 r/min), a higher proportion of high-angle grain boundaries (77.1 %) formed when the rotation speed was 3600 r/min, which effectively reduced the defect density. At the same time, recrystallization in a large area lowered the energy storage in the grain, which further alleviates the corrosion. In addition, the second phase dominated by Mg2Si was fine and uniformly distributed, which also reduced the galvanic corrosion tendency. Therefore, high corrosion resistance was obtained using HRS-SFSP. On the other hand, continuously increasing the rotation speed coarsened the grains and the second phase,which decreased the corrosion resistance.

Influence of Metal Cations on Corrosion Behavior of Aluminum Alloy 2024-T3 in Model Freshwater

The influence of metal cations on corrosion behavior of aluminum alloy (AA2024-T3) in model freshwater was examined by immersion experiments, surface analysis, and electrochemical measurements. After long-time immersion, the corrosion rate of AA2024-T3 decreased as the corrosion indicator Y increased, and the corrosion rate of the alloy was reduced by Zn2+. The specimen immersed in Zn2+ containing solution showed less corrosion products which were observed by scanning electron microscopy (SEM). The results of X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) showed that Zn2+ attaches to aluminum alloys and forms protective layers. Electrochemical impedance spectroscopy (EIS) results suggested that Zn2+ reduced the area of defects in the passive film.

Experimental study of corrosion behavior on 7005 aluminum alloy under acidic 3.5 wt% NaCl environment

AbstractThe corrosion failure behavior of 7005 aluminum alloy is a critical issue in the durability studies of vessels operating. In this study, the corrosion behavior of aluminum alloy 7005‐T4 in 3.5 wt% NaCl solution with pH 2, pH 4, and pH 6 was investigated by surface observation, electrochemical, and mechanical testing. The experiment results that the corrosion susceptibility is more at a solution of pH 2 compared with that at pH 4 and pH 6. The maximum depth and width of corrosion pits increase linearly with aggravation of corrosion. In addition, the probability distribution of the corrosion pit depth in each corrosion environment, which generally follows a Lognormal distribution, is statistically analyzed. The tendency of stress−strain curves at the elastic−plastic transition stage indicated that corrosion has an effect on mechanical performance, and revealed that corrosion promotes the advance of the plastic deformation stage. Fractography indicated the presence of a quasi‐cleavage zone beneath the corrosion layer. The results provide theoretical guidance for safe service and design guidelines for 7005 aluminum alloy.

Corrosion behavior of aluminum alloy in simulated nuclear accident environments regarding the chemical effects in GSI-191

Long-term aluminum (Al) corrosion tests were designed to investigate the condition that would generate severe Al corrosion and precipitation. Buffer agents of sodium tetraborate (NaTB), trisodium phosphate (TSP) and sodium hydroxide (NaOH) were adopted. The insulation materials, fiberglass and calcium silicate (Ca-sil), were examined to explore their effects on Al corrosion. The results show that significant precipitates were formed in both NaTB/TSP-buffered solutions at high pH. The precipitates formed in NaTB solution raise more concerns on chemical effects in GSI-191. A passivation layer formed on the surfaces of coupon in solution with the presence of insulations could effectively mitigate Al corrosion. The Fe-enriched intermetallic particles (IPs) embedded in coupon appeared to serve as seeds to readily induce precipitation via providing extra area for heterogeneous Al hydroxide precipitation. X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses indicate that the precipitates are mainly boehmite (γ-AlOOH) and no direct evidence confirms the presence of sodium aluminum silicate or calcium phosphate.

Application of X-Ray Computed Tomography to Assess the Effect of Elevated Temperature on Atmospheric Corrosion of Aluminum Alloy 6063 in Contact with FeCl3 Droplets

The atmospheric corrosion behavior of aluminum alloy 6063-T5 with exposure to FeCl3 containing droplet deposits to simulate direct contact with steel corrosion product droplets has been investigated. Experiments were performed at 50°C and compared to room temperature exposure conditions to assess the behavior of aluminum heatsink materials. The evolution of corrosion sites, penetration rates, and corrosion product chemistry was analyzed using x-ray computed tomography, Raman spectroscopy, and electron microscopy techniques. The measured corrosion rates were lower when the temperature was raised, even when exposed to multiple wet-dry periods. The lower corrosion rates were attributed to a reduced propensity to form iron oxyhydroxides/oxides at the aluminum surface, which were present after room temperature exposure. The results are discussed in light of the galvanic corrosion behavior of aluminum alloy in contact with liquid steel corrosion products.

Effect of pH and Concentration on Electrochemical Corrosion Behavior of Aluminum Al-7075 T6 Alloy in NaCl Aqueous Environment

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl− and OH−) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.