Corrosion Resistance Of Aluminum Alloys Research Articles

Corrosion resistance of aluminum fluoride modified 6061 aluminum alloy

The oxide film formed naturally on the surface of aluminum alloy is easy to be damaged in marine and lake environment, resulting in corrosion and damage of aluminum alloy matrix materials. Compared with alumina, aluminum fluoride has excellent chemical stability. It is insoluble in acid, alkali and most organic solvents. In this study, polyvinylidene fluoride (PVDF) was used as the surface treatment material. A protective layer of aluminum fluoride was deposited on the surface of aluminum alloy by chemical vapor deposition. The coating enables the corrosion potential of aluminum alloy shift positively and decreases the corrosion current, indicating improved corrosion resistance of aluminum alloy.

Corrosion Behavior of AA 1100 Anodized in Gallic-Sulfuric Acid Solution

Sulfuric acid anodization is one of the common methods used to improve corrosion resistance of aluminum alloys. Organic acids can be added to the sulfuric acid electrolyte in order to improve the properties of the anodized aluminum produced. In this study, the use of gallic acid as an additive to the sulfuric acid anodization of AA1100 was explored. The effect of varying anodization current density and gallic acid concentration on the properties of anodized aluminum samples was observed using electrochemical impedance spectroscopy, linear polarization, and scanning electron microscopy. It was observed that the corrosion resistance of samples anodized in gallic-sulfuric acid solution at 10 mA·cm−2 is lower than samples anodized in sulfuric acid. It was also observed that higher anodization current density can lead to lower corrosion resistances for aluminum samples anodized in gallic-sulfuric acid solution. However, samples anodized at 5 mA·cm−2 and at a gallic acid concentration of 5 g·L−1 showed better corrosion performance than the samples anodized in sulfuric acid only. This suggests that the use of low amounts of gallic acid as an additive for sulfuric acid anodization can lead to better corrosion resistances for anodized aluminum.

Effects of anodizing surface treatment on the mechanical strength of aluminum alloy 5083 to fibre reinforced composites adhesive joints

In this study, the anodizing process based on the use of tartaric sulfuric acid solution (TSA) was carried out on metal substrate to evaluate for the first time its effect on the adhesion strength and corrosion resistance of aluminium alloy (i.e., AA5083) to fibre (i.e., basalt or glass) reinforced composite adhesive joints for nautical applications. Furthermore, some TSA anodized samples were soaked in a NaOH solution to investigate the influence of this post-immersion step on the joint performances. With the aim to improve the fibre-matrix adhesion in the composite substrate thus further increasing the overall mechanical response of the joint, glass and basalt fibres were treated with a silane coupling agent solution. The corrosion behaviour of the aluminium alloy was studied by electrochemical techniques. Samples morphology was analysed by scanning electron microscopy, while the interaction between aluminium alloy substrate and epoxy resin was studied through contact angle analysis and resin uptake tests. The effectiveness of the silane treatment was examined by means of Fourier transform infrared spectroscopy and quasi-static tensile tests carried out on dry glass and basalt fabrics. The mechanical response of the resulting joints was evaluated by means of quasi-static tensile tests in accordance to ASTM D3528 standard.

Effect of Heat Treatment and Sulfuric Acid Anodization on Corrosion Resistance of Aluminum Alloy (AA7075)

This paper, studied the effect of heat treatment and anodization on corrosion resistance of aluminum alloy 7075 (AA7075), with a view to improving its corrosion resistance. Microstructure and micro hardness of the anodic film of the samples were studied with the aid of optical metallurgical microscope and automated micro hardness testing machine. Linear polarization methods were used to assess the corrosion behaviour of the alloy in 0.5M HCl. The microstructure of the annealed sample showed formation of dendrites while precipitation hardened samples in palm kernel oil and SAE 40 engine oil showed precipitates of MgZn2. The SEMS result showed pores and micro cracks on the surfaces of the anodized samples, with the as cast and anodized sample in sulfuric acid exhibiting most compact with few pores. The as cast and sulfuric acid anodized sample shows highest micro hardness value of 205.33 HV, while the least value of 150.67 HV was recorded in sample precipitation hardened in SAE 40 engine oil and anodized in sulfuric acid. Analysis of the potentiodynamic polarization data and curves showed a linear relationship (decrease in icorr, decreases the corrosion rate) between current density and the corrosion rate in all the samples. Higher polarization resistance of 15.093 Ω/cm2 was recorded by the as cast and Sulfuric acid (SA) anodized sample while the precipitation treated in SAE 40 engine oil plus SA anodized sample recorded lowest polarization resistance of 5.2311 Ω/cm2. Heat treatment alone improves corrosion resistance of AA 7075 in 0.5 M HCl solution but heat treatment plus SA anodization does not improve corrosion resistance in the same environment.

Bimodal Microstructure Obtained by Rapid Solidification to Improve the Mechanical and Corrosion Properties of Aluminum Alloys at Elevated Temperature

The demand for aluminum alloys is increasing, as are the demands for higher strength, with the aim of using lighter products for a greener environment. To achieve high-strength, corrosion-resistant aluminum alloys, the melt is rapidly solidified using the melt-spinning technique to form ribbons, which are then plastically consolidated by extrusion at elevated temperature. Different chemical compositions, based on adding the transition-metal elements Mn and Fe, were employed to remain within the limits of the standard chemical composition of the AA5083 alloy. The samples were systematically studied using light microscopy, scanning electron, and transmission microscopy with electron diffraction spectrometry for the micro-chemical analyses. Tensile tests and Vickers microhardness were applied for mechanical analyses, and corrosion tests were performed in a comparison with the standard alloy. The tensile strength was improved by 65%, the yield strength by 45% and elongation by 14%. The mechanism by which we achieved the better mechanical and corrosion properties is explained.

Protection enhancing of threaded connections of light-alloy drill pipes against contact corrosion

When using light-alloy drill pipes (LAIDP) with steel tool joints, the development of contact corrosion is observed under certain operating conditions. The value of corrosion mainly depends on the difference in electrochemical potential (ECP) of the contacting metals. One of the effective methods for increasing the corrosion resistance of aluminum alloys is the micro-arc oxidation (MAO) method. This is an electrochemical process in combination with micro-arc-discharges phenomena at the anode-electrolyte border, which allows forming ceramic coatings of aluminum oxides on the surface, including its high-toughness and wear-resistant phase - α-Al2O3 (corundum). MAO-technology is a highly efficient and environmentally friendly process. At the forming of such a coating on the threaded part and in the tool joint zone of the pipe, a barrier for contact corrosion between the steel tool joint and the surface of the aluminum pipe is created. In this work, contact corrosion on samples in a pair of 1953T1 aluminum alloy - 40KhN2MA steel in a 5% NaCl solution at 80 °C was investigated. The data obtained showed the effectiveness of using protective MAO-coating to reduce contact corrosion and increase the reliability of the tool joint threaded connection of LAIDP.

Corrosion Resistant Superhydrophobic Aluminum Alloy: A Review

Aluminum alloys are widely used in aerospace and space applications due to their high strength to weight ratio. The most prevalent method to prevent corrosion of aluminum alloys is anodic oxidation or anodization treatment. The anodized layer is porous and hence there are chances of penetration of moisture and corrosion of underlying substrate underneath the anodized layer. Surface modification of the aluminum alloy by superhydrophobic coating is a very attractive method to improve the corrosion resistance of aluminum alloys. The inspiration for the fabrication of superhydrophobic coatings is obtained from various examples in nature such as strider’s legs and lotus leaf. The fabrication of superhydrophobic coatings involves two important steps; generation of a rough surface and deposition of low surface energy material. The present paper reviews the various researches undertaken for the production of superhydrophobic surfaces on aluminum and aluminum alloys. Finally, the scope of future research activities in the fabrication of superhydrophobic coatings has been discussed in the paper.

Technological assurance of the quality of processing of products from aluminum alloys with a complex geometric shape using magnetic abrasive processing

In the presented article, the issue of the implementation of magnetic abrasive processing is considered in order to ensure the quality of surfaces of complex shapes of parts made of corrosion-resistant aluminum alloys. The implementation was carried out through theoretical and experimental research. In a theoretical study, the features of processing corrosion-resistant aluminum alloys, existing and possible schemes for magnetic-abrasive processing of surfaces of complex geometric shapes, including a combination of various working movements of the workpiece and pole pieces, are considered. In an experimental study, the dependence of the quality of the processed surface (roughness) on the size of the working gap between the workpiece and the working pole was determined. The result of the research is the determination of the optimal treatment schemes for surfaces with a complex geometric shape, as well as the derived exponential dependence of the change in surface roughness on the size of the working gap.

Сorrosion resistance of the welded junction of aluminum alloy of the Al-Mg-Si-Cu system

The results of complex investigations of corrosion resistance of aluminum alloy of the Al-Mg-Si-Cu doping system have been presented. By the method of metallography, it has been found that under the influence of the thermal cycle of welding, the secondary phases are separated and coagulation of insoluble phases occurs. The base alloying elements form metastable phases in the process of crystallization of seams, which are evenly distributed, but differ in size and shape. In the zone of thermal influence, the decomposition of the supersaturated solid solution and the dissolution of the strengthening phases, the characteristic feature of which is the instability of decomposition within the limits of one grain, the enrichment of the boundary areas with alloying elements, and the depletion of volume, are observed. This is accompanied by the formation of thin eutectic layers along the boundaries of crystallites. The results of electrochemical investigations have shown that the potential of the weld and the high effected zone (HAZ) is more noble compared to the base metal. Taking into account a larger area of the base metal in the construction compared to the weld (the weld area does not exceed 10% of the area of the base metal), a satisfactory resistance of the weld to the continuous corrosion can be expected in general. The depth of intergranular corrosion of the weld joint of the Al-Mg-Si-Cu system alloy is (0.245-0.350) mm, which is greater than for the base metal – from 0.082 to 0.086 mm. An increasing of the depth of destruction of the grain boundaries in the weld joint confirms the fact that the near-weld zone is weakening during welding. Welding does not worsen the resistance of welds to the exfoliation corrosion compared to the base metal, which is estimated by the ball 2-3 for the base metal and the ball 1 for the weld and HAZ. The stability of the weld under conditions of a simultaneous effect of constant loading and full immersion into the corrosive medium is reduced: the time until the destruction of the base metal is from 67 to 88 hours, of the weld – from 1 to 49 hours. Since the resistance to the exfoliation corrosion of the weld is satisfactory, the performance of the welded product as a whole, under conditions of a joint effect of corrosion-aggressive medium and mechanical stress, will be determined by the stability of HAZ against pitting and intergranular corrosion.

Preface

The 9th International Conference on Materials Science (ICMS2020) was held at the National University of Mongolia from September 10 to 13, 2020 in Ulaanbaatar. Unfortunately, the global pandemic had a bad effect on the event. Therefore, some of the participants could not attend the conference in person. A significant part of the participants (more than 50 people) were accommodated in the hall and more than 25 people participated in absentia. Since at this time it is difficult to predict the end of the pandemic, and the termination of the exchange and discussion of scientific results may negatively affect the research of many scientific groups, it was decided to hold this traditional conference using video presentations. Participants from Russia presented their reports and presentations in electronic form (video reports and posters) and were demonstrated at section meetings. In total - about 80 participants.Organisers were some known scientific organizations:National University of Mongolia, Ulaanbaatar, Mongolia, National University of Mongolia, Mongolia, Inner Mongolian Normal University, China, Institute of Physical Materials Science, Siberian Branch of the Russian Academy of Sciences, Russia, Mongolian Academy of Sciences, Mongolia, German-Mongolian Institute for Resources and Technology and Erdenet Mining Corporation SOE, Mongolia.Scientific committee was consisted of famous scientists:Prof. J.Davaasambuu (National University of Mongolia)Prof. U.Pietsch (University of Siegen, Germany)Prof. G.Eckold (University of Goettingen, Germany)Prof. O.Tegus (Inner Mongolian Normal University, China)Dr. A.Nomoev (IPMS SB RUS, Russia)Prof. S.Gorfman (Tel Aviv University, Israel)Prof. S.Bardakhanov (Buryat State University, Russia)Prof. P.Daniel (Le-Mans University, France)Prof. B.Battsengel (GMIT, Mongolia)Dr. B.B.Damdinov (SFU, Krasnoyarsk, Russia)Acad. O.Penyazkov (A.V.Lykov Institute, Belarus)Acad. D.Sangaa (Mongolian Academy of Sciences)Acad. J.Temuujin (Mongolian Academy of Sciences)Dr. V.Koledov (IRE, RAS, Russia)Dr. P.Altantsog (Mongolian Academy of SciencesAll materials were reviewed by the editors: Dr. N. Tuvjargal and Prof. J.Davaasambuu from Department of Physics, Faculty of Arts and Sciences, National University of Mongolia.The conference consisted of plenary presentations for 30 minutes and session reports for 15 minutes. There were 35 oral reports and 29 posters in total. The organizers have provided 5 minutes for questions that can be asked in person or via the Internet.The objectives of the conference were to bring together scientists working in the field of materials science from around the world, to exchange ideas, recent research results in this area and to offer a platform for the initiation of scientific cooperation between Mongolian and foreign scientists. The conference was focused on the structures, properties and applications of new materials as well as their characterization techniques.Topics were: Materials science, Condensed matter physics, Computational methods, Experimental methods and instrumentation, Laser spectroscopy.At the conference, nanotechnology-related studies related to quantum effects, such as carrier tunneling, controlled changes in the structure of energy bands, quantization of energy spectra of charge carriers and spin phenomena, and the study of new physical features of semiconductor nanostructures, were discussed. The topic were a description of the transport properties of various ion-exchange membranes, crystallization of supercooled liquids and amorphous solids, increase the corrosion resistance of aluminum alloys, obtaining nanoscale metal and alloy powders. Numerical simulation of phonon crystals with time-dependent properties of a periodic structure, computer simulation by the molecular dynamics method, the processes of structure formation of nanoclusters of an alloy of silver and copper were presented.The organizers and participants of ICMS 2020 noted the high scientific level of the presented reports.

Galvanic Corrosion Behavior between Aluminum and Iron in Chloride Solutions at Near-Neutral pH and Corrosion Prevention By Anodizing

The joints between steels and aluminum alloys are expected to be used as multi-material structures due to their low cost, high stiffness, and high corrosion resistance. When aluminum alloys are connected to steels, galvanic corrosion is expected to occur because the corrosion potentials of aluminum alloys are lower than those of iron and steels. In the case of the galvanic corrosion in chloride solutions at near-neutral pH, the anodic reaction on aluminum alloys are oxide film formation and/or pitting. For pure Al and aluminum alloys, the generation of localized corrosion is evaluated by the critical potential for localized corrosion, such as pitting potential. In this study, the electrode potential under galvanic coupling and pitting potential were compared. Surface modification is effective methods for improvement on corrosion resistance of aluminum alloys. However, there is little research related to the galvanic corrosion between steels and aluminum alloys. In this research, the galvanic corrosion behavior of pure aluminum coupled to pure iron in chloride containing near-neutral pH solutions and the effect of anodizing on galvanic corrosion were investigated.Pure iron and pure aluminum were prepared as specimens in this research. The specimen surface of aluminum was polished down to 0.25 µm with a diamond paste. The iron surface was also polished down to 1 µm with a diamond paste. Diluted synthetic seawater (200 mg/L Cl-, pH 8.2) was used as the electrolyte for electrochemical measurements. The electrode area was ca. 10 mm2. Ag/AgCl (3.33 M KCl) was used as the reference electrode. Galvanic currents and electrode potentials were measured. The distance between iron and aluminum electrodes was kept at 10 mm. A zero resistance ammeter was used to measure the galvanic currents. The electrode potential of pure aluminum was also measured. Additionally, anodizing in sulfuric acid was conducted to pure aluminum in various voltages and times. Galvanic current measurements were carried out between these anodized specimens and pure iron to evaluate the effect of anodizing on galvanic corrosion prevention.The galvanic currents and electrode potentials of pure aluminum coupled to pure iron were measured. The galvanic currents were anodic currents. The oscillations of galvanic currents and electrode potentials were generated during the measurements. Filiform corrosion was observed on pure aluminum after the measurements. The generation of filiform corrosion was caused by higher electrode potentials of pure aluminum coupled to pure iron compared with the initiate potential for filiform corrosion.The time variation of galvanic currents and electrode potentials of anodized aluminum coupled to pure iron were also measured in the diluted synthetic seawater (pH 8.2). Pure aluminum specimens were anodized at 4, 8 and 16 V at 18 s. The oscillations were observed in the galvanic currents of anodized aluminum (4 and 8V); however, no oscillation was measured on the specimen anodized at 16 V. After the measurements, pitting was observed on anodized aluminum (4 and 8V). However, no pitting was observed on the specimen anodized at 16 V. The thickness of anodic oxide film was measured. It was confirmed that the thickness of the oxide film increased with anodizing voltage. Consequently, it was indicated that the galvanic corrosion resistance of pure aluminum for galvanic corrosion was enhanced by the increase of the thickness of the oxide film.

Investigation of Metal Cation Effects on Corrosion Behavior of Aluminum Alloys

Introduction Due to excellent mechanical property and corrosion resistance, aluminum alloys are widely used in airplanes, automobiles, and kitchen utensils. The corrosion resistance of aluminum alloys relies on highly protective and reformative passive films. However, the passive films are destroyed in presence of chloride ions, and the corrosion rate of aluminum alloys depends on the concentration of chloride ions 1 - 3. A few studies have shown the corrosion behavior of aluminum alloys in freshwater; however, the corrosion rates of aluminum alloys were changed in freshwater which sampled different place 4. Because freshwater also contains some metal cations in dilute concentration. The authors expected that the metal cations changed the corrosion rate of aluminum alloy in freshwater. The authors have been investigated the corrosion of A3003 aluminum alloy in freshwater focused on the effects of metal cations5 - 8. The corrosion rate of A3003 aluminum alloy is changed with metal cations in model freshwater despites the concentration of chloride ions, dissolved oxygen and pH are the same. The researches also clarified that Zn2+ is the best metal cation to inhibit the freshwater corrosion of A3003 among the metal cations used6, 7. An Auger spectroscope was used to investigate the corrosion morphology and composition of corrosion products of A3003 formed in model freshwater with different Zn2+ concentration8. From the cross-sectional AES point analysis, it has been clarified that the corrosion products have multi-layer structure.However, it is not fully elucidated the role of the metal cations on the corrosion behavior of aluminum alloys. The purpose of this study is to investigate the effects of metal cations on corrosion behavior of aluminum alloys in aqueous environment. Experimental Sheets of aluminum alloys (A7075, A6061and A2024) were used as the specimens. The sheets were cut into 7 7 mm for immersion corrosion tests, and 10 10 mm for electrochemical measurements. The specimens were grounded with SiC abrasive paper. Before the tests, specimens were cleaned in highly purified water and in ethanol using ultrasonic bath.Model solutions of 1 molm-3 NaCl (NaS), 0.5 molm-3 MgCl2 (MgS), and 0.5 molm-3 ZnCl2 (ZnS) were used in this experiment. The pH of the model solutions was maintained at around neutral.Electrochemical tests were carried out in a three-electrode cell using a potentiostat. An 4 cm2 Pt plate and an Ag/AgCl-saturated KCl electrode were used as the counter and the reference electrodes. Before the measurements, the specimens were immersed in the solutions for 3.6 ks (1 h) at 298 K. Electrochemical impedance spectroscopy (EIS) tests were carried out in the frequency range from 1 mHz to 10 kHz, and the modulation amplitude of the applied sinusoidal wave was 10 mV.Specimens were immersed in the model freshwater for 2.59 Ms (30 d) and 0.6 Ms (7 d) at 25 ºC. The mass of a specimen was measured before and after the test. Surface analysis were carried out by scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS). Results From the immersion tests, the mass of specimens increased after immersion in the solutions and corrosion behavior of aluminum alloys was changed with the metal cations present in the solutions. Independent of used alloy, SEM images clearly showed the deposited corrosion products on the surface. Uniform deposition of corrosion products was observed on the specimen immersed in ZnS as compared to the NaS and MgS. EDS results demonstrated the presence of zinc-related products on the specimen immersed in ZnS XPS results suggested that zinc ions were incorporated in the oxide films of aluminum alloy and increased the corrosion resistance property of the oxide films. EIS results showed the highest impedance in ZnS as compared to the other solutions. References 1) T. H. Nguyen and R. T. Foley, Journal of the Electrochemical Society, 127, 2563-2566 (1980).2) R. T. Foley, Corrosion, 42, 277-288 (1986).3) B. Zaid, D. Saidi, A. Benzaid, and S. Hadji, Corrosion Science, 50, 1841-1847 (2008).4) Editorial board of Japan Aluminium Association: "Aluminum Handbook. Tokyo", Japan Aluminium Association, (2007), p 73.5) K. Otani, M. Sakairi, T. Kikuchi, and A. Kaneko, Zairyo-to-Kankyo, 59, 330-331(2010).6) M. Sakairi, K. Otani, A. Kaneko, Y. Seki, and D. Nagasawa, Surface and Interface Analysis, 45, 1517-1521 (2013).7) K. Otani, M. Sakairi, R. Sasaki, A. Kaneko, Y. Seki and D. Nagasawa, Journal of Solid State Electrochemistry, 18, 325-332 (2014).8) K. Otani, Md. Saiful Islam, M. Sakairi, and A. Kaneko, Surface and Interface Analysis, 51, 1207-1213 (2019).

Investigation on corrosion behaviour of aluminium 6061-T6 alloy in acidic, alkaline and salt medium

Aluminium 6061 is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements. T6 temper 6061 has an ultimate tensile strength of at least 290 MPa (42,000 psi) and yield strength of at least 240 MPa (35,000 psi). More typical values are 310 MPa (45 ksi) and 270 MPa (39 ksi), respectively. Corrosion acts on a continuous basis and it is a tedious issue to normalize it or to eradicate it. Hardened aluminium alloy containing Magnesium and Silicon as its major alloying elements. This research work deals with investigating the corrosion behaviour of this Aluminium 6061-T6 reaction in the acidic alkaline and in the salt medium. By analyzing the comparative results it will clarify that the Aluminium 6061 T6 alloy has higher corrosion rate in alkaline solution than in the acidic solution. The corrosion resistance of aluminium alloy is higher in solutions of acids and salts containing sulfate and nitrate ions than in chloride ions.

Increasing the corrosion resistance of aluminum alloys when modified

The corrosion properties of aluminum alloys of AI-Mg, AI-Mg-Sc and Al-Ѕi systems before and after modification were studied. Tests were made for intergranular, layered corrosion and corrosion cracking of AMg6, AL4 alloys. The results showed the modification efficiency of aluminum alloys AL4 by silicon carbide. In order to stabilize the structure, increase the corrosion resistance and the performance properties of aluminum alloys, experiments were conducted on the treatment of liquid melts with nanosized compositions based on silicon carbide. The research materials were foundry and deformed aluminum alloys of AI-ЅI, AI-Mg-Ѕс, AI-Mg systems. Promising directions of modification of aluminum alloys in the world are conducted in the field of application of powder modifiers. The use of such modifiers facilitates the technological process, is environmentally safe, leads to a uniform distribution of the introduced nanocompositions over the crosssection of the casting, which increases the strength, plastic properties of the alloys and their stability. Іndustrial enterprises of Ukraine apply modification of foundry aluminum alloys with sodium salts. To increase the complex of physical and mechanical properties and to achieve the required technological characteristics, including weldability, a complex modifier was used to provide grinding of the structure of aluminum alloys Processing of aluminum melts was performed by a nanosized tablet modifier based on silicon carbide using the developed technology. A modifier with a particle size of up to 100 nm was obtained by the method of plasma chemical synthesis. The initial and modified alloys were tested for general intercrystalline and stratification corrosion by standard methods. In modified alloys found intercrystalline corrosion. Corrosion cracking did not even occur after 55 days of testing

Precipitation hardening and intergranular corrosion behavior of novel Al–Mg–Zn(-Cu) alloys

High-performance aluminum alloys are desired for applications that require lightweight materials, but it is challenging to overcome the tradeoff between their strength and intergranular corrosion resistance. To overcome this tradeoff, we have prepared novel Al–Mg–Zn (-Cu) alloys with highly Zn content combined with Cu addition. The alloys with a (Zn + Cu)/Mg ratio below 1.5 are different from traditional 2000, 5000 and 7000 series aluminium alloys. The results show that the number density and lattice spacing of intragranular precipitates increase, while the precipitate sizes decreases with the increase of (Zn + Cu)/Mg ratio, which is the reason for the increase of the alloy strength. Meanwhile, the intergranular corrosion resistance of the alloys is also enhanced by decreasing the potential between grain boundary precipitates and the Al matrix, especially in alloys with high (Zn + Cu)/Mg ratios. These results provide a new method for obtaining high-strength and corrosion-resistant aluminum alloys.

Effect of different laser energy densities on the corrosion resistance of aluminum alloys

Purpose Laser cleaning, as a new type of cleaning technology, has the advantages of environment-friendliness, better selectivity, better controllability and higher efficiency compared to traditional chemical cleaning or grinding. This paper aims to use ultra-fast surface laser cleaning equipment built in laboratory to study the influence of different energy density (7.6, 11.5 and 15.3 J/cm2) on corrosion resistance of the aluminum alloy A7N01P-T4, a high-speed train body material. Design/methodology/approach SEM, white light interferometer, EDS and XPS were used to analyze the surface morphology, roughness, element content and oxide layer composition of aluminum alloy before and after cleaning. The corrosion resistance was studied by electrochemical experiments and exfoliation corrosion experiments. Findings The results showed that new oxide scale was formed on the surface after laser cleaning. The changes of surface roughness and chemical composition of oxide scale made a significant influence on corrosion behaviors. Better corrosion resistance was obtained with the energy density increased, and at the energy density of 11.5 J/cm2, aluminum alloy exhibited the best corrosion resistance. Research limitations/implications The paper only studies specific aluminum alloys and is not universal. Laser cleaning equipment is set up for the laboratory and has not yet been put into industrial production. Practical implications This paper indicated that ultra-fast laser processing was a new direction for the development of industrial equipment surface cleaning and carried out ultra-fast laser of aluminum alloy surface cleaning had certain research significance for its corrosion resistance. Social implications Compared with the conventional cleaning methods such as air abrasives grinding or chemical cleaning, laser cleaning has advantages of environment-friendliness, better selectivity, better controllability and higher efficiency. Laser cleaning can not only protect the environment, but also improve cleaning efficiency. Originality/value Changes in the surface of aluminum alloys after ultra-fast surface laser treatment were found, and the mechanism of changes in aluminum alloy corrosion properties was clarified.

Effect of Low energy laser shock peening on plastic deformation, wettability and corrosion resistance of aluminum alloy 7075 T651

AA 7075 T651 alloys are often used in a variety of applications such as gears, shafts, chassis in automobile industries, missiles and extension tubes of rifles in defense and marine components, where wear and corrosion resistance is indispensable. It entails the enhancement in surface characteristics such as hardness, wear resistance and resistance to the corrosion emanate from high concentration of chlorides. This article is devoted to analyze the corrosion behavior of AA 7075 T651 alloy in 3.5 % NaCl solution subjected to the surface modification by low energy (200 mJ, 300 mJ and 400 mJ) pulsed Laser Shock Peening (LSP). Among the unpeened and peened specimens the specimen peened with pulse energy of 400 mJ exhibited the highest Ecorr value of −1200 V and lowest Icorr value of 0.0221 mA/cm2 in the potentiodynamic polarization test. The electro chemical impedance spectroscopy revealed a superior resistance to the localized corrosion. Further, the investigations on the variations in microstructure, plastic strain, dislocation density and Wettability due to LSP are carried out using Transmission Electron Microscope, Scanning Electron Microscope, X-ray diffraction (XRD) and Goniometry instrument. Besides the reduction in the grain size and 31 % increment in the micro strain, a transformation from hydrophilic to hydrophobic nature is observed in the specimen peened with 400 mJ LSP.

Comparative study of corrosions of aluminum alloys 2024 and 6101 at various pH values

The corrosion behaviors of aluminum alloys 2024 and 6101 were studied in a medium with different pH values. The selected pH values were 2, 4, 6, 9, 11 and 13. Weight-loss tests were performed to assess the corrosion rate at these pH values, and analysis of electrochemical properties was conducted for the corrosion at pH = 4 and 11 in particular. The results showed that the corrosion rates of the aluminum alloys increased with the increase of the acidity or alkalinity of the corrosive medium. The corrosion resistance of aluminum alloy 6101 was better than that of aluminum alloy 2024 under neutral and acidic conditions; however, corrosion resistance of aluminum alloy 2024 was superior to that of aluminum alloy 6101 under alkaline conditions. The corrosion of aluminum alloy 6101 was very severe in a highly alkaline medium, and the corrosion rate reached an average value of 29.96 mm/year in an environment of pH = 13, with a large number of corrosion pits on the surface of the corroded sample.

Electrochemical Investigation of the Effect of Process Parameters on the Corrosion Behavior of Aluminum-Cladded Pressure Vessel Steel Using a Friction Stir Diffusion Cladding Process

Surface cladding and coatings are commonly used to protect structures against corrosion in corrosive environments. In this paper, electrochemical properties of friction stir diffusion cladded ASTM A516-70 with corrosion-resistant aluminum alloy grade 5052 are studied. The effect of process parameters, tool rotational and traverse speeds on the corrosion behavior of produced cladded steels was comparatively assessed. Electrochemical analyses revealed that the cladded steel sample provided good corrosion protection performance in comparison with the un-cladded steel substrate following an immersion test of up to 21 days in 3.5% NaCl medium. Increasing the tool traverse speed was found to negatively affect the corrosion resistance. Optimum parameters for the selected cladding system were found to be a 500 rpm tool rotational speed, and a 50 mm/min tool traverse speed for protection against general corrosion. Meanwhile, higher traverse speed demonstrated stable passivation behavior and, therefore, lower propensity for pitting localized corrosion. Post characterization of the exposed area indicated that tool shoulder marks were favorable spots for the accumulation of corrosion products.

Microstructure, synergistic mechanism and corrosion behavior of tin oxide conversion film modified by chitosan on aluminum alloy surface

In this paper, a chitosan‑tin oxide composite film (CTOF) composed of clusters of micro-flowers was prepared on aluminum alloy to improve corrosion protection in the 0.1 M H2SO4 and 0.001 M NaF acidic solution by the hydrothermal method. The surface morphology of the film was analyzed by scanning electron microscopy (SEM). The structure and ingredient of the film were research by using X-Ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). The method we used is very simple, convenient and pollution-free. The film shows good protective efficiency as high as 99.998% in solution of 0.1 M H2SO4 and 0.001 M NaF which indicates that the films can improve corrosion resistance of aluminum alloy under acidic solution.