Corrosion Resistance Of Aluminum Research Articles

Enhancing aluminum corrosion resistance by two-step anodizing process

Two-step anodizing process can be seen as an effective way to form an adhesive and continued layer on aluminum to enhance its corrosion resistance. Anodic alumina was produced by two types of anodization process, namely single-step and two-step anodizing. We have then evaluated their protection effectiveness against aluminum corrosion in aggressive medium (NaCl 3%). In both cases, X-ray diffraction reveals an amorphous nature of porous oxide films. The electrochemical impedance spectroscopy (EIS) results revealed a strong correlation between the corrosion performance and the morphology of the development anodic films. Also, these results indicated that the morphology and the corrosion resistance of anodic film formed by two-step anodizing process are very improved if compared to single one.

Fe와 galvanic couple된 알루미늄의 내식성에 미치는 마그네슘의 영향

Effects of magnesium and pH on corrosion of aluminum galvanically coupled to iron have studied by using potentio- dynamic and static tests for polarization curves, Mott-Schottky test for analysis of semiconductor property, and GD-AES and XPS for film analysis. Pitting potential was sensitive to magnesium as an alloying element but not to pH, while passive current was sensitive to pH but not to magnesium. It was explained with, instead of point defect model (PDM), surface charge model describing that the ingression of chloride depends on the state of surface charge and passive film at film/solution interface is affected by pH. In addition, galvanic current of aluminum electrically coupled to iron was not affected by magnesium in pH 8.4, 0.2M citrate solution but was increased by magnesium at the solution of pH 9.1. The galvanic current at pH 9.1 increased with time at the initial stage and after the exposure of about 200 minute, decreased and stabilized. The behavior of the galvanic current was related with the concentration of magnesium at the surface. It agreed with the depletion of magnesium at the oxide surface by using glow discharge atomic emission spectroscopy (GD-AES). In addition, pitting potential of pure aluminum was reduced in neutral pH solution where chloride ion maybe are competitively adsorbed on pure aluminum. It was confirmed by the exponential decrease of pitting potential with log of [] around 0.025 M of [] and linear decrease of the pitting potential. From the above results, unlike magnesium, alloying elements with higher electron negativity, lowering isoelectric point (ISE), are recommended to be added to improve pitting corrosion resistance of aluminum and its alloys in neutral solutions as well as their galvanic corrosion resistance in weakly basic solutions.

Enhancing Pitting Corrosion Resistance of Aluminium by Anodizing Process

Enhancing Pitting Corrosion Resistance of Aluminium by Anodizing Process

Fabrication and Corrosion Resistance of Superhydrophobic Hydroxide Zinc Carbonate Film on Aluminum Substrates

Superhydrophobic hydroxide zinc carbonate (HZC) films were fabricated on aluminum substrate through a convenient in situ deposition process. Firstly, HZC films with different morphologies were deposited on aluminum substrates through immersing the aluminum substrates perpendicularly into aqueous solution containing zinc nitrate hexahydrate and urea. Secondly, the films were then modified with fluoroalkylsilane (FAS: CH3(CF2)6(CH2)3Si(OCH3)3) molecules by immersing in absolute ethanol solution containing FAS. The morphologies, hydrophobicity, chemical compositions, and bonding states of the films were analyzed by scanning electron microscopy (SEM), water contact angle measurement (CA), Fourier transform infrared spectrometer (FTIR), and X‐ray photoelectron spectroscopy (XPS), respectively. It was shown by surface morphological observation that HZC films displayed different microstructures such as microporous structure, rose petal‐like structure, block‐shaped structure, and pinecone‐like structure by altering the deposition condition. A highest water contact angle of 156.2° was obtained after FAS modification. Moreover, the corrosion resistance of the superhydrophobic surface on aluminum substrate was investigated using electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements’ results revealed that the superhydrophobic surface considerably improved the corrosion resistance of aluminum.

Effects of High-Pressure Torsion on the Pitting Corrosion Resistance of Aluminum–Iron Alloys

Effects of High-Pressure Torsion on the Pitting Corrosion Resistance of Aluminum–Iron Alloys

The role of Metal-Matrix Composite development During Friction Stir Welding of Aluminum to Brass in Weld Characteristics

The present research aims to investigate the development of brass reinforced aluminum composites during dissimilar friction stir welding of brass and aluminum. Moreover, to probe the effect of such a metal matrix composite on its bed, the cross-sectional properties of joint area are studied in two aspects of corrosion behavior and hardness distribution. Microstructural investigations through optical and electron microscopy show development of lamellar composites within the top site of the stir zone and aluminum surface. The measured iso-hardness contours indicate that evolved composite structures increase the cross-sectional hardness of aluminum locally. Also, the electrochemical assessment of joint area suggests that Al/Br composite structure plays an accelerative role in deterioration of cross-sectional corrosion resistance of aluminum through obstructing passivation and forming microgalvanic cells, where cathodic brass reinforcements intensify the corrosion of anodic aluminum matrix.

Investigation on the explosive welding mechanism of corrosion-resisting aluminum and stainless steel tubes through finite element simulation and experiments

To solve the difficulty in the explosive welding of corrosion-resistant aluminum and stainless steel tubes, three technologies were proposed after investigating the forming mechanism through experiments. Then, a 3D finite element model was established for systematic simulations in the parameter determination. The results show that the transition-layer approach, the coaxial initial assembly of tubes with the top-center-point the detonation, and the systematic study by numerical modeling are the key technologies to make the explosive welding of LF6 aluminum alloy and 1Cr18Ni9Ti stainless steel tubes feasible. Numerical simulation shows that radial contraction and slope collision through continuous local plastic deformation are necessary for the good bonding of tubes. Stand-off distances between tubes (D 1 and D 2) and explosives amount (R) have effect on the plastic deformation, moving velocity, and bonding of tubes. D 1 of 1 mm, D 2 of 2 mm, and R of 2/3 are suitable for the explosive welding of LF6-L2-1Cr18Ni9Ti three-layer tubes. The plastic strain and moving velocity of the flyer tubes increase with the increase of stand-off distance. More explosives (R>2/3) result in the asymmetrical distribution of plastic strain and non-bonding at the end of detonation on the tubes.

Improved corrosion and wear resistance of Mg alloys via laser surface modification of Al on AZ31B

A highly intense laser beam from a continuous wave diode-pumped ytterbium laser source was used to synthesize a corrosion and wear resistant aluminum coating rich in Al 12Mg 17 intermetallic phase by direct melting of aluminum precursor powders on AZ31B Mg alloy substrates. The coating composition and microstructure were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and high resolution energy diffraction spectroscopy in a transmission electron microscope. From X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy diffraction spectroscopy analysis it was confirmed that laser processing resulted in uniform distribution of a highly corrosion resistance Al 12Mg 17 intermetallic phase within the coating. The effect of this type of coating on the corrosion and wear resistance of the Mg alloy is investigated in the current study. Under the set of laser processing parameters employed in the current work, no significant change in microstructural and phase evolution and thereby corrosion and wear performance was observed for the laser processed samples. In general improved corrosion resistance was observed for the laser processed samples as compared to the untreated AZ31B. Also, as the precipitation of an intermetallic phase is expected to strain harden the matrix, an improvement in dry sliding wear was observed for the laser processed samples.

The effect of extrusion speed on the structure and corrosion properties of aged and non-aged 6063 aluminum alloy

Extrusion is used in processing of Al alloy for consolidation, redistribution of reinforcements, and shape forming. The important parameter that controls the extrusion process is extrusion rate, which is a function of extrusion equipment and parameters. Homogenized AA6063 alloy billets were extruded at different ram speeds related to extrusion speed (3, 6, 10 mm s −1) and then aged at 185 °C for 6 h. The extruded samples were studied for their corrosion, microstructure, and mechanical properties. The effects of extrusion speed and aging on the corrosion behavior of AA6063 were investigated using dynamic polarization and impedance techniques in 0.5 M NaCl aqueous solution. The surface structures were then characterized by means of surface profilometer. The electrochemical measurements showed that the decreasing ram speed for the aged sample improved the corrosion resistance. In addition, the aging improved the corrosion resistance of aluminum in 0.5 NaCl environments.

SEM-EDS characterization of natural products on corrosion inhibition of Al-Mg-Si alloy

The corrosion resistance of aluminum and its alloys is the subject of tremendous technological importance due to their increased industrial applications. The corrosion protections and the mechanism of corrosion inhibitions of natural products for an Al-Mg-Si alloy in seawater were investigated at room temperature. The surface morphology was studied by means of macro scale electrochemical techniques and localized microscopic methods, i.e., Scanning electron microscope (SEM) with associated elemental analysis by energy dispersive spectrometer (EDS). SEM examinations provided morphological characterization of the surface of Al-Mg-Si alloy sample before and after immersion in seawater; meanwhile surface analytical techniques by the EDS allowed us to investigate detail the chemical composition of aluminum oxide layers. The experiments were performed with Al-Mg-Si alloy, immersed in a 5 L beaker containing seawater with and without the natural products for 60 days at room temperature. The SEM results indicate that the natural products (natural honey, vanillin, and tapioca starch) absolutely inhibited the corrosion products on the specimen surfaces. They also protected the passive film from dissolution in seawater. The EDS spectrums were determined that carbonaceous, carbonyl, methoxy and hydroxyl groups as functional groups of natural products in inhibition mechanism.

Al 5052 합금의 저입열 Pulse MIG 최적 현장 용접조건 산정에 관한 실험적 연구

The weight reduction of the transportations has become an important technical subject Al and Al alloys, especially Al 5052 alloys have been being applied as door materials for automobile. One of the most widely known car weight-reduction methods is to use light and corrosion-resistant aluminum alloys. However, because of high electrical and thermal conductivity and a low melting point, it is difficult to obtain good weld quality when working with the aluminum alloys. Also, Pulse MIG welding is the typical aluminum welding process, but it is difficult to apply to the thin plate, because of melt-through and humping-bead. In order to enhance weld quality, welding parameters should be considered in optimizing the welding process. In this experiment, Al 5052 sheets were used as specimens, and these materials were welded by adopting new Cold Metal Transfer (CMT) pulse process. The proper welding conditions such as welding current, welding speed, torch angle <TEX>$50^{\circ}$</TEX> and gap 0~1mm are determined by tensile test and bead shape. Through this study, range of welding current are confirmed from 100A to 120A. And, the range of welding speed is confirmed from 1.2m/min to 1.5m/min.

ChemInform Abstract: Improvement in the Corrosion Resistance of Alumina in Caustic Alkaline Solutions Obtained by Dispersing Ceria-Doped Tetragonal Zirconia Particles

ChemInform Abstract: Improvement in the Corrosion Resistance of Alumina in Caustic Alkaline Solutions Obtained by Dispersing Ceria-Doped Tetragonal Zirconia Particles

FATIGUE PROPERTIES OF ALUMINUM ALLOY (A6061-T6) WITH ULTRASONIC NANO-CRYSTAL SURFACE MODIFICATION

The corrosion resistance of aluminum can be improved by adding alloy elements or using a surface heat treatment process. The machine quality can be confirmed by analyzing the surface roughness, the surface hardness and the residual stress. In this paper, the fatigue characteristics of A6061-T6 aluminum specimens were obtained and compared with those of the treated specimens with the UNSM (Ultrasonic Nano-Crystal Surface Modification) technology and the untreated ones by using a multi-spindle rotating bending fatigue testing machine. The fatigue crack initiation and fatigue lives of the treated specimens with the UNSM technology was delayed and extended by the UNSM effects that are the increase of surface hardness, and the reduction of the surface roughness.

Role of nanostructure in pitting of Al–Cu–Mg alloys

Aluminium alloys possess a unique combination of strength and low density, which historically have made these alloys ideal for many structural applications. However, addition of alloying elements in appreciable concentrations, in particular Cu and Mg, make Al-alloys inherently susceptible to localised corrosion. In this work, we adopt a bottom-up approach in an attempt to quantify the critical microstructural feature size (viz. precipitate size) that is capable of triggering a cascade of pitting events and eventual degradation of corrosion resistance. This is accomplished by exploiting the well characterised hardening response in a model alloy, Al–1.1Cu–1.7Mg (at.%), for which pitting resistance of the alloy was tracked with aging time and hence microstructural evolution. Corrosion performance and microstructural characterisation were carried out using a combination of electrochemical testing, coupled with high-resolution scanning transmission electron microscopy (HRSTEM) and atom probe tomography (APT). Results indicate, at least for this particular alloy, that second phase features below a critical width of approximately 3 nm can be tolerated from a corrosion perspective. This study has potentially wide consequences in the understanding of aluminium alloy corrosion initiation and the development of highly corrosion resistant aluminium alloys.

Aluminium corrosion inhibition using benzene‐1,2,4,5‐tetracarboxylic dianhydride (PMDH)

PurposeThe purpose of this paper is to study the inhibitory activity of benzene‐1,2,4,5‐tetracarboxylic dianhydride (PMDH) on aluminium corrosion in hydrochloric acid 1 M HCl.Design/methodology/approachThe inhibitive effect of PMDH towards the corrosion of aluminium in 1 M HCl solution is studied by means of electrochemical impedance spectroscopy, polarization curves (LSV) and scanning electron microscopic techniques. The effect of inhibitor concentration and temperature against inhibitor action is investigated.FindingsIn the presence of inhibitor (PMDH), the corrosion resistance of aluminium is improved and the corrosion rate and corrosion current are reduced, therefore the inhibition efficiency and polarization resistance are increased. With increasing temperature and decreasing inhibitor concentrations, the rate of aluminium corrosion increased. The surfactant acts as mixed type inhibitor and obeys a Langmuir isotherm.Originality/valueThe results shown in this paper are an insight to the understanding of the corrosion resistance and electrochemical behaviour of aluminium for future industrial applications and development.

Oxidative post-treatments for enhanced corrosion resistance of aluminium electrodeposited from ionic liquids

In this paper we report the results of a study on the corrosion properties of carbon steel (UNI Fe360B) coated with a thin aluminium layer electrodeposited from ionic liquids and subsequently post-treated in an oxidizing environment. Two different types of treatments were investigated: thermal oxidation in air and electrochemical anodization. We found that heat treatments provided only a modest improvement of the anticorrosion properties while the electrochemical treatment produced a significant improvement.

Study on Technological Process of Cerium-Based Conversion Coating on Aluminum

The Cerium-based conversion coating is formed on the industrial aluminum(1060) by using chemical immersion. The microstructures of the conversion coating have been examined by scanning electron microscopy(SEM). The electrochemical measurement result shows that the corrosion resistance of aluminum is significantly improved after the conversion coating was formed. The result of X-ray photoelectron spectroscopy (XPS) shows that the cerium conversion coating mainly consisted of oxide of aluminum, CeO2 and TiO2. The formation mechanism of the Cerium-based conversion coating is investigated.

New Application of the “Underwater Super-Hydrophobic” Surface in the Corrosion Protection

“Underwater super-hydrophobic” surface applied in the corrosion protection was prepared by melting myristic acid (CH3(CH2)12COOH) adsorbed onto the anodized aluminum. The static contact angle for seawater on the surface was measured to be 154°. The surface structure and composition were then characterized by means of scanning electron microscopy (SEM) with energy dispersive X-ray spectrum (EDX) and atomic force microscope (AFM). The electrochemical measurements showed that the super-hydrophobic surface significantly improved the corrosion resistance of aluminum in sterile seawater.

Super-hydrophobic surface treatment as corrosion protection for aluminum in seawater

“Underwater super-hydrophobic” surface applied in the corrosion protection was prepared by melting myristic acid (CH 3(CH 2) 12COOH) adsorbed onto the anodized aluminum. The static contact angle for seawater on the surface was measured to be 154°. The surface structure and composition were then characterized by means of scanning electron microscopy (SEM) with energy dispersive X-ray spectrum (EDS) and atomic force microscope (AFM). The electrochemical measurements showed that the super-hydrophobic surface significantly improved the corrosion resistance of aluminum in sterile seawater. In addition, the mechanism of the underwater super-hydrophobic surface applied in the corrosion resistance was discussed using a schematic.

Deposition of nanostructured crystalline and corrosion resistant alumina film on bell metal at low temperature by rf magnetron sputtering

Aluminium oxide films deposited by rf magnetron sputtering for protective coatings have been investigated. The alumina films are found to exhibit grainy surface microstructure. The grain size, structure and density depend on different system parameters such as argon and/or oxygen flow rate and applied rf power etc. The effect of transition of the discharge from metallic to reactive mode on the surface characteristics of the alumina film is studied. X-ray diffractometry reveals that in poisoned mode of sputtering and under optimized power and pressure, crystalline alumina film can be grown. Different system conditions are optimized for corrosion resistant aluminium oxide films with good adhesion properties. Nanostructured alumina film is obtained at lower pressure (8 × 10 −4 to 9 × 10 −4 Torr) by rf reactive magnetron sputtering.