Alloys In NaCl Solution Research Articles

Optimal corrosion resistance of cobalt-based dual-phase entropic alloys via compositional modulation of aluminum

A new category of Al-doped cobalt-based dual phase entropic alloys with high corrosion resistance properties was designed in the present work. CALPHAD (CALculation of PHAse Diagram) aided prediction was performed to facilitate the alloy design. Two groups of alloys have been extensively investigated by various techniques. One group was quenched in water from the homogenization temperature (i.e. 1200 °C) to room temperature. The other group was subsequently quenched in liquid nitrogen from room temperature. The microstructure of the proposed alloys was characterized by X-ray diffraction (XRD). Several kinds of electrochemical tests were performed to study the corrosion behaviors of the designed alloys in NaCl solution, including open circuit potential (OCP), polarization and cyclic polarization curves, electrochemical impedance spectroscopy (EIS), electrochemical noise (ECN), linear voltammetry curves and staircase voltammetry scan, and Mott–Schottky method. The obtained results show that Al has a minor influence on the corrosion property of this series alloy with a 0 to 2 at.% Al addition. All the designed alloys hold quite acceptable corrosion resistance. In addition, a mechanical property, i.e. micro-hardness, is also provided as a supplement information. This work sheds light on the correlation between computational thermodynamics and corrosion behaviors in cobalt-based dual-phase entropic alloys, as well as to provide a feasibility study on the important role of CALPHAD method for a rapid development of a new category of high performance alloys.

The effect of permanent magnet stirring on the corrosion resistance of Sn-2.0Ag-0.5Cu-2Zn solder alloys in NaCl solution

Permanent magnet stirring (PMS) is adjusted to increase the alloy corrosion resistance by modifying the crystallographic texture. According to the findings, the lamellar structure had been converted into equiaxed grains by the PMS processing. Following exposure to a 3.5 wt percent NaCl solution, the corrosion behavior of the Sn-2.0Ag-0.5Cu-2Zn alloy was examined using electrochemical methods (polarization and electrochemical impedance spectroscopy (EIS)) and surface analysis using SEM, EDX and XRD. According to the PDP curves, the PMS treatment procedure significantly reduces the values of corrosion current density (icorr) and shifts the corrosion potential (Ecorr) to more positive noble values. The Ecorr values of SAC (205)-2Zn and SAC (205)-2Zn with PMS are increased from −936.66 to −756.18 mV (vs. SCE). Also, the pitting resistance is higher in case of PMS treated alloy as indicated from cyclic polarization (CP). PMS treated alloy possess higher Erep values than Ecorr values, confirming the ability of passive film to restore itself. EIS data showed that the diameter of capacitive loop for PMS-treated SAC (205)-2Zn alloy is approximately four times as the untreated alloy indicating less corrosion rate and higher protection.

Insight into mitigation of corrosion behavior of novel chalcone derivative for AZ91 Mg alloy in saline solution: synthesis, characterization, electrochemical and adsorption studies

Magnesium is the lightest structural metallic element, and exhibited an important developmental potential due to the growing need for lightweight electronics and transportation (aerospace, automobile, etc.). A novel chalcone derivative 4-(3-(4-(4-((4-(4-(3-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acryloyl)-5-methyl-1H-1,2,3-triazol-1-yl)phenyl)sulfonyl)phenyl)-5-methyl-1H 1,2,3-triazol-1-yl)-3-oxoprop-1-en-1-yl)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (DMPO) was synthesized. The chemical structure of the newly synthesized DMPO was inferred from its spectral data (H1-NMR, C13-NMR, and FT-IR). Its structure was also affirmed by field emission scanning electron microscopy-energy dispersive X-ray (SEM-EDX), and thermal stability was studied by thermal gravimetric analysis (TGA-DTA). Then, its potency as a remarkable corrosion inhibition for AZ91 magnesium alloys in NaCl (3.5 wt%) solution was studied. Hydrogen evolution, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) investigations were utilized to assess the impact of the newly synthesized chalcone derivative DMPO on the electrochemical performance of AZ91 Mg alloy in NaCl solution (3.5 wt%). SEM-EDX was used to evaluate the surface and elemental analysis of an AZ91 Mg alloy immersed in NaCl solution (3.5 wt%) with and without DMPO inhibitor. The obtained electrochemical evaluation revealed that DMPO functions as a high-performance, environmentally friendly AZ91 Mg alloy inhibitor in NaCl (3.5%) recording inhibition efficiency 93.7% at 100 ppm. Potentiodynamic polarization experiments revealed that the corrosion was inhibited due to the adsorption of inhibited molecules which follows the Langmuir adsorptive process. The findings also affirmed the development of protective film on Mg alloy surface. In electrochemical tests, it was discovered that DMPO molecules were mixed-type corrosion inhibitors.

Effect of scandium on microstructure and corrosion resistance of Ti64 alloy in NaCl solution

Effect of scandium on microstructure and corrosion resistance of Ti64 alloy in NaCl solution

Corrosion behavior of single- and poly-crystalline dual-phase TiAl-Ti3Al alloy in NaCl solution

Corrosion behavior of single- and poly-crystalline dual-phase TiAl-Ti3Al alloy in NaCl solution

Effect of harmonic structure on the electrochemical behavior of high entropy Cantor alloy in NaCl solution

The present work discusses the effect of harmonic structure on the corrosion behavior of high entropy Cantor alloy (Fe20Cr20Mn20Ni20Co20) in freely aerated 3.5 wt% NaCl solution. A harmonic structure featuring a continuous shell region with an average grain diameter of ∼3 μm and discreet core regions with an average grain diameter of ∼25 μm is developed in the Cantor alloy. The X-ray diffraction patterns, transmission electron microscopy and selected area electron diffraction patterns confirm the presence of face-centered cubic phase indicating that no second phase formation occurs in the shell or core regions. Its electrochemical behavior has been studied and compared with a conventional Cantor alloy, harmonic-structured 304L stainless steel, and maraging steel. The studies conclude that the harmonic-structured Cantor alloy shows the highest corrosion resistance among the tested materials. A novel mechanism for the corrosion of the harmonic-structured Cantor alloy suggests that the excellent corrosion-resistive properties are attributed to the early passivation by enrichment of Cr in the oxide layer in its shell region and reversal of polarity due to the early passivation during corrosion.

Electrochemical corrosion and electrochemical migration characteristics of SAC-1Bi-xMn solder alloys in NaCl solution

The effects of Ag and Mn content were investigated from the electrochemical corrosion (ECC) and electrochemical migration (ECM) point of view in the case of SAC0307–1Bi-xMn and SAC305 lead-free solder alloys in NaCl solution. On the one hand, long-term results showed that lower silver content showed higher corrosion resistance. On the other hand, the microstructure and elemental composition of the dendrites formed after the ECM test were investigated by transmission electron microscopy (TEM) and energy dispersive X-ray spectrometer (EDS) which demonstrated that micro-alloying elements (i.e. Mn) also contributed to the ECM processes. The ECM model of Mn was also established.

Sodium dodecyl sulfate (SDS) as an effective corrosion inhibitor for Mg-8Li-3Al alloy in aqueous NaCl: A combined experimental and theoretical investigation

The corrosion inhibition behavior of Mg-8Li-3Al alloy in NaCl solution with sodium dodecyl sulfate (SDS) was investigated by hydrogen analysis, scanning electron microscopy (SEM), electrochemical test, scanning Kelvin probe force microscopy (SKPFM) and computational methods. Results showed that the corrosion resistance of Mg-8Li-3Al alloy in NaCl solution was effectively improved with SDS. The SEM and SKPFM results confirmed a dense, 200 nm-thick SDS-adsorbed layer had formed on the alloy surface. The separation energy ∆ E gap and adsorption energy E ads of SDS on the Mg surface were calculated by density functional theory and molecular dynamics simulations, respectively. And the corrosion inhibition mechanism was hypothesized and described.

Effect of grain refinement induced by wire and arc additive manufacture (WAAM) on the corrosion behaviors of AZ31 magnesium alloy in NaCl solution

Abstract Additive manufacturing (AM) of Mg alloys has become a promising strategy for producing complex structures, but the corrosion performance of AM Mg components remains unexploited. In this study, wire and arc additive manufacturing (WAAM) was employed to produce single AZ31 layer. The results revealed that the WAAM AZ31 was characterized by significant grain refinement with non-textured crystallographic orientation, similar phase composition and stabilized corrosion performance comparing to the cast AZ31. These varied corrosion behaviors were principally ascribed to the size of grain, where cast AZ31 and WAAM AZ31 were featured by micro galvanic corrosion and intergranular corrosion, respectively.

Effect of Cr addition on corrosion behavior of cupronickel alloy in 3.5 wt% NaCl solution

Cupronickel alloys have a variety of applications in marine engineering due to their good mechanical and corrosion properties. In this work, the effect of Cr on the corrosion behavior of Cu–10Ni–1.6Fe–0.5Mn alloy in 3.5 wt% NaCl solution was investigated through electrochemical and surface characterization. The results indicate that Cu–10Ni–1.6Fe–0.5Mn–0.3Cr alloy has better corrosion resistance performance compared to Cu–10Ni–1.6Fe–0.5Mn alloy in NaCl solution. The addition of Cr reduces the corrosion current density of cupronickel alloys from 7.82 μA/cm2 to 7.10 μA/cm2. The better corrosion resistance performance of the Cu–10Ni–1.6Fe–0.5Mn–0.3Cr alloy could be mainly attributed to the incorporation of Cr3+ ions in Cu2O lattice during corrosion. The corrosion product film of Cu–10Ni–1.6Fe–0.5Mn–0.3Cr alloy mainly contains the compounds including Cu2O, NiO, γ-FeOOH, Cr2O3, and Cu2(OH)3Cl. The formation of Cr2O3 can further enhance the stability of corrosion film and improve the corrosion properties of the alloy.

The effect of Mn addition on corrosion behaviour of equiatomic CoCrFeNi high entropy alloys in NaCl solution

ABSTRACT The corrosion behaviour of equiatomic CoCrFeNi and CoCrFeNiMn high entropy alloys manufactured by the vacuum arc melting were studied in 3.5 wt-% NaCl solution. And the reasons for the differences in corrosion resistance were investigated in terms of microstructure, electrochemical behaviour and oxide film. The results show that the two alloys exhibit different corrosion characteristics, with CoCrFeNi alloy displaying typical passivation characteristics and CoCrFeNiMn alloy exhibiting activation behaviour. The CoCrFeNi HEA with compact and protective passive film has lower corrosion current density, larger film resistance and polarisation resistance, meaning a lower corrosion rate and superior corrosion resistance compared with those of CoCrFeNiMn alloy. Moreover, CoCrFeNiMn alloy forms a discontinuous and loose corrosion product film with higher Mn content and lower contents of Cr, Fe and Co compared to the matrix, which decreases its protection performance. The addition of Mn changes the electrochemical behaviour, and higher Mn oxides/hydroxides within oxide film are unfavourable to forming a stable passive film.

The Corrosion Behavior of Al-Cu-Li Alloy in NaCl Solution

Al-Cu-Li alloys are widely used in aerospace due to their excellent mechanical properties. However, the surface of Al-Cu-Li alloy components is prone to localized corrosion, when it serves in humid environments such as the ocean, due to the action of moisture in the air and Cl− in the atmosphere. Therefore, it is significant to study the corrosion performance of typical third-generation Al-Cu-Li alloys in a marine environment. The corrosion tests of the experimental materials are carried out in different concentrations of NaCl solution, and their morphology and maximum corrosion depth are characterized to evaluate their corrosion resistance at a particular time. The corrosion behavior of the third generation typical Al-Cu-Li alloys (2A97-T3, 2A97-T6, 2060-T8, and 2099-T83) and high-strength Al alloy 2024-T4 in solution containing Cl− is investigated using correlative immersion testing. The results show that 2A97-T3 possesses the best corrosion resistance performance of all under the same concentration of NaCl solution and soaking time. The corrosion resistance performance of 2024-T4 is respectively stronger than that of 2060-T8 and 2099-T83, but weaker than that of 2A97 (T3, T6). The corrosion morphologies of 2060-T8 and 2099-T83 are characterized by deep pits and large areas of exfoliation corrosion, while the corrosion morphology of 2099-T83 is the worst, indicating that its corrosion resistance is the weakest of all. The local corrosion preferentially occurred in the boundary region between intermetallic compounds or precipitates and alloy matrix in NaCl solution, and the lithium is selectively dissolved during the dissolution process, which brings about the enrichment of copper-containing residues. Subsequently, the copper-rich residue serves as the cathodic relative to the Al matrix, which leads to the anodic dissolution of the peripheral Al matrix occurs.

Electrochemical properties and dissolved behavior of laser solid formed Ti6Al4V alloy in NaCl solution with different current densities

The hybrid manufacturing process of additive manufacturing (AM) and electrochemical machining (ECM) is a new approach to advanced manufacturing technology. The feasibility of using ECM to machine an as-deposited Ti6Al4V alloy fabricated by the laser solid forming (LSF) method of AM was investigated in 15 wt.% NaCl solution. As the machining current density increased, the material removal rate increased linearly, and the current efficiency dropped from 140% to 93%. The current efficiency over 100% at low current densities was attributed to the electrochemical reactions of atoms in lower valence states. The microdissolved grooves, resulting from selective preferential dissolution of the α phase, were shallowed when machined at a higher current density (>3 A cm −2 ) and are attributed to the weakening of the galvanic effect at higher machining voltages. Additionally, the dissolved surface topography exhibited the worst waviness at the delimited current density of 10 A cm −2 , and the surface waviness decreased rapidly as the current density increased in the positive delimited range. Considering the machining efficiency and the surface quality of ECM, the as-deposited Ti6Al4V machined at a current density of 40 A cm −2 will be the preferred ECM current parameter.

Corrosion and passivation behavior of 6082‐T6 aluminum alloy in NaCl solution

AbstractThe corrosion and passivation behaviors of 6082‐T6 aluminum alloy in 1.5 wt% NaCl solution with natural aeration were investigated by segmented electrochemical measurement combined with scanning electron microscope, transmission electron microscope, and X‐ray diffractometer. The results showed that the active Mg dissolved from Mg2Si promoted the development of intergranular corrosion (IGC) and that local dissolutions of the matrix around the Si and AlFeMnSi particles are the initial sites for pitting corrosion. The passivation overlying the IGC crack is interacted by the cations in the layer and the ions, resulting in the intergranular cracking of the passive film. The cracks near the secondary phase meet the cracks developing along the grain boundary, resulting in the failure of the passive film in the form of networks.

Effect of pH on corrosion behavior of Al-Mg-Si alloy in NaCl solution

Effect of pH on corrosion behavior of Al-Mg-Si alloy in NaCl solution

Inhibition of hydrogen absorption due to wear between Ni–Ti superelastic alloys in NaCl solution by H2O2 addition

• Ni–Ti superelastic alloy absorbs hydrogen due to wear in NaCl solutions without marked corrosion. • The amount of hydrogen absorbed in NaCl solutions is almost as much as that in purified water. • The hydrogen absorption due to wear is inhibited by adding a small amount of H 2 O 2 into solutions. The inhibition of hydrogen absorption due to wear between Ni–Ti superelastic alloys in 0.15 M NaCl solution has been attempted by adding H 2 O 2 . For comparison with previous results in purified water, the present wear test has been conducted under the same conditions as in the previous test except for the test solutions. The amounts of wear loss and hydrogen absorbed during the wear test in the NaCl solution without H 2 O 2 are almost as much as those in water, suggesting hydrogen embrittlement. Upon the addition of 0.01 M H 2 O 2 into the NaCl solution, the corrosion potential during the wear test shifts in the noble direction; the amount of absorbed hydrogen substantially decreases. The present results indicate that the addition of a small amount of H 2 O 2 into solutions is effective for the inhibition of hydrogen absorption due to wear.

A stearic acid/polypyrrole-based superhydrophobic coating on squeeze-cast Mg-Sr-Y-Ca-Zn alloys for improved salt-water corrosion

A polypyrrole (PPy) and stearic acid (SA)-based superhydrophobic coating was developed to improve the corrosion behavior of squeeze cast Mg-1.0 wt% Sr-1.0 wt% Y-0.6 wt% Ca-0.5 wt% Zn alloy in NaCl solution. The structure and morphology of the coating were analyzed using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), three-dimensional optical surface profilometer, glancing angle X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy (XPS) reveals variable coating thickness ranging from ~25–120 μm (depending on Mg alloy pretreatment with/without NaOH prior to coating) comprised of primarily Mg, C, O, Cl, and Zr species ascribed to a mixed composition of PPy, Mg(OH)2, and low amount of ZrO2 with mud-crack features and petal-like clusters. Although SA/PPy-based superhydrophobic coating (contact angle of static water droplets ~1640) can improve the corrosion resistance of bare Mg alloy drastically owing to the presence of thin air cushion between NaCl solution and Mg alloy surface preventing saltwater infiltration and advancement of Cl−-ions towards reactive Mg surface, however, the surface pretreatment in NaOH salt bath before superhydrophobic surface treatment has a profound effect on the interphase, bonding, and stability of the coating with Mg and associated corrosion phenomena. The Mg alloy without NaOH pretreatment (NPT) demonstrated excellent instantaneous corrosion resistance in 0.1 M NaCl confirmed by potentiodynamic polarization, polarization resistance (RP), and coating resistance (Rcoat) measured by electrochemical impedance spectroscopy (EIS). On the contrary, NaOH pretreated Mg alloys (1MPT, 5MPT) exhibited excellent corrosion protection ability (up to ~4-5 h) during long-term EIS study owing to the presence of Mg(OH)2 thick film deposited during pretreatment acting as a protective barrier preventing PPy degradation and Mg2+-ion diffusion to the outward surface. Overall, SA/PPy-based superhydrophobic coating juxtaposed with/or without surface pretreatment can shed new insight into the corrosion phenomena of squeeze cast Mg alloy in NaCl solution.

Improvement of Corrosion Resistance of the AZ91 Magnesium Alloys with Sputtered Aluminum Layer Using Interdiffusion Treatment, Anodic Oxidation Treatment and Sealing Process

Magnesium alloys have low corrosion resistance due to their high chemical activity. Therefore, it is necessary to improve their corrosion resistance to use in corrosive environments. In the present study, we aimed to improve the corrosion resistance of AZ91 magnesium alloy in NaCl solution, using aluminum sputtering deposition, anodic oxidation treatment and sealing process were examined. To evaluate the corrosion rate, electrochemical experiments were carried out. In the case of just aluminum sputtering deposition, corrosion resistance was not improved due to small defects in the sputtering deposition. However, corrosion resistance was improved by sputtering deposition followed by interdiffusion treatment at 553 K for more than 3 hours. Corrosion resistance was further improved by anodic oxidation treatment and sealing process after the interdiffusion treatment. With this series of treatments, the corrosion rate of the samples was reduced to 1/360 compared to that of AZ91 base metal. The results show that the interdiffusion treatment, anodic oxidation treatment and sealing process after sputtering deposition are significantly effective to improve corrosion resistance of AZ91 magnesium alloy.

Effect of Zn addition on the corrosion behaviours of as-cast BCC Mg-11Li based alloys in NaCl solution

Effect of Zn on the corrosion behaviours of Mg-11Li-xZn (x = 0, 1, 3, 6; termed as L11, LZ111, LZ113, LZ116) alloys in 0.1 M NaCl solution has been investigated. The results reveal that corrosion resistance of four alloys increases following the order LZ116 < LZ113 ≈ L11 < LZ111. Besides, filiform-like corrosion occurs at early corrosion stage for the four alloys, while additional pitting corrosion preferentially emerges in the L11, LZ113 and LZ116 alloys with immersion time. The small alloying Zn can reduce corrosion rate of Mg-11Li alloys, and excess Zn will accelerate the corrosion due to the existence of micro-galvanic effect between second phase and matrix. Regarding of the surface film, double layers of considerable thick outer layer and inner layer can be observed on the top of L11 and LZ111. Nevertheless, small alloying Zn is prone to modify the surface film and contributes to the high corrosion resistance of LZ111 alloy, while high Zn concentration results in the rapid corrosion damage of surface films on the LZ113 and LZ116 alloys and further elevate corrosion rate.

The Anisotropic Electrochemical Machinability of Laser Cladding Deposited Ti6Al4V Alloy in NaCl Solution

The hybrid manufacturing method of laser cladding deposition (LCD) additive manufacturing and electrochemical machining (ECM) is a promising approach to advanced manufacturing technology for difficult machined materials. The anisotropic electrochemical performance of LCD-produced Ti6Al4V alloy was studied in 15 wt.% NaCl solution by polarization curve measurements and ECM tests. The horizontal-plane (X0Y plane) exhibits a more stable passive film in both static electrolyte and low current density ECM processes than the vertical-plane (X0Z plane). Additionally, the horizontal-plane exhibits a higher material removal rate and more consistent dissolved surface roughness in comparison with the vertical-plane during the high current density ECM process. The microstructure of the LCD-produced Ti6Al4V alloy on the horizontal-plane consisted of equiaxed-like prior-β grains and slightly finer α-laths but was composed by columnar prior-β grains and coarser α-laths on the vertical-plane. These differences in the microstructural characteristics produce the distinctions observed in the electrochemical dissolution behavior and electrochemical machinability on the horizontal- and vertical-planes.