Alloys In NaCl Solution Research Articles

Improving environmental adaptability and long-term corrosion resistance of Mg alloys by pyrazole ionic liquids: Experimental and theoretical studies

The influence of pyrazolium ionic liquid 1-n-butyl-2-decylpyrazole bistrifluoromethanesulfonimide ([BDePz][NTf2]) on the corrosion behavior of AZ91D magnesium alloys in NaCl solution with three different concentrations and ASTM D1384-87 corrosive solution was explored by electrochemical measurements and SEM, AFM. Results revealed that as the concentration of Cl− increases, the corrosion inhibition performance of magnesium alloy inhibitor is slightly lower, but still good. The maximum corrosion inhibition efficiency is 90.4% in 0.05 wt% NaCl and 82.0% in ASTM D1384-87 corrosive solution. After soaking in the inhibitor-ethanol solution, the surface of the magnesium alloy is still relatively smooth after soaking in the four corrosion solutions for 7 d. The possible inhibition mechanism is proposed according to the XPS and XRD results as well as the molecular dynamics simulations and quantum chemical calculations.

Performance of different microstructure on electrochemical behaviors of laser solid formed Ti–6Al–4V alloy in NaCl solution

The effect of different heat treatment on electrochemical behavior of laser solid formed Ti–6Al–4V alloy in 15 wt% NaCl solution was systematically investigated. Microstructure characteristics including phase volume fractions and elemental segregation after different heat treatment and the electrochemical anodic behaviors related to the polarization tests and passivation process were analyzed. The electrochemical results show that the annealed sample has slightly better corrosion resistance owing to more uniform element distribution compared with solution treatment and aging samples. Different EIS results and defect concentrations between the passivation films formed on the two samples found that element distribution has significant effect on stability of the passivation films.

Autocatality effect of AlCl3 applications on the oxidation process of amorphous Al87Ni8Y5 alloy in 0.5 M aqueous NaCl solution

Investigation of corrosion resistance of amorphous metal alloy ( AMA ) from aluminum is carried out in 0.5 M aqueous solutions of NaCl. Cl- ions penetrate the oxide layer through pores or defects and can colloidally disperse the oxide film and increase its permeability . The Al 87 Ni 8 Y 5 were obtained by melt spinning technique in helium atmosphere onto a copper wheel with a circumferential speed of about 30 m/sec (cooling rate = 10 6 К/sec). The method of voltammetry in the potential-dynamic mode showed that the introduction of AlCl 3 (7.4·10 -3 mol/l) in the system of origin reduces the first maximum, which is responsible for the adsorption of Н + on the AMА electrode. A potentiostatic ivestigates of the behavior of Al 87 Ni 8 Y 5 in 0.5 M aqueous NaCl solution with additional elements AlCl 3 indicates the autocatalytic properties of a low concentration of AlCl 3 (2·10 -7 mol/l), which contributes to the dissolution of the surface. The kinetics of establishing the stationary potential in 0.5 M aqueous NaCl solution and with AlCl 3 applications were chronopotentiometrically investigated. The presence of AlCl 3 ions in the background electrolyte during chronopotentiometry of AMA Al 87 Ni 8 Y 5 in 0.5 M aqueous sodium chloride solution reduces the position of the potential dependence. To independently confirm the influence of Al 3+ and Cl - ions on the processes of formation of protective layers on the surface of Al 87 Ni 8 Y 5 in 0.5 M aqueous NaCl solution using a electron microscope. Micrographs of the alloy surface were taken after VA removal in NaCl background solution 1M application of AlCl 3 , the surface of the alloy in NaCl solution is covered with a thin layer of oxides and hydroxides of aluminum, and due to the sweep potentials in the range of -1000 ÷ +300 mV in the presence of AlCl 3 a multilayer coating is formed. Keywords: amorphous metallic alloys, passivation layers, corrosion resistance.

The role of trace Ag in controlling the precipitation and stress corrosion properties of aluminium alloy 7N01

The effect of trace Ag on the early precipitation and the resistance to stress corrosion cracking (SCC) of peak-aged 7N01 alloy (Al-4.5Zn-1.55Mg-0.12Cu) were investigated. A characterization method known as three-dimensional atom probe (3DAP) was used in this research to investigate the precipitation behaviors of the alloy. When 0.12 wt % Ag is present in the alloy, the solid solubility of the alloy increases after the solid-solution treatment at 485 °C and quenching in water. In the early stage when the alloy is aged at 120 °C, Ag atoms will enrich around the clusters (GPI zones and GPII zones) giving rise to more nucleation sites for them. As the ageing time goes on, these clusters will transform into high-density η′ phase and then the hardness and mechanical strength of the alloy will increase. Three kinds of precipitates with different sizes in the alloy after peaking ageing were found by high resolution transmission electron microscopy (HRTEM). The results obtained from the high angle annular dark field of scanning transmission electron microscope (HAADF-STEM) show that Ag atoms are distributed around η′ phase in the matrix and η phase in the grain boundaries, which significantly increases the corrosion resistance of the alloy in NaCl solution after peak ageing. The results from the slow strain rate test (SSRT) and the observation of fracture morphologies show that for the alloy with trace Ag addition and after peak ageing, the resistance to SCC is improved, as well as the size and the distribution distance of the precipitate (MgZn2) in the grain boundaries increase.

Effect of Applied Cathodic Potential on Friction and Wear Behavior of CoCrMo Alloy in NaCl Solution

Most of the reported work on the effect of applied potential on tribocorrosion or corrosive wear of metallic alloys in a corrosive environment were conducted at anodic potentials. Limited tests have been conducted at cathodic potentials for comparison purposes or to derive the pure mechanical wear component in tribocorrosion. This work investigated the effect of cathodic potential on the friction and wear behaviour of an important biomedical alloy, CoCrMo, sliding against an Al2O3 slider in 0.9% NaCl solution at 37 °C. High friction was found at cathodic potentials close to the open circuit potential, where mechanical wear played a predominant role in material removal. At potentials more cathodic than the hydrogen charging potential, low friction and low wear were observed. The coefficient of friction (COF) and total material loss decreased with increasing cathodic potential, such that at −1000 mV (saturated calomel electrode, SCE), extremely low COF values, as low as 0.02, and negligible material loss were obtained. Such reductions in friction and wear at increasing cathodic potentials were accompanied with the formation of parallel lines in the sliding track and were gradually diminished with increasing applied contact load. It is believed that hydrogen charging and hydrogen segregated layer formation at the surface are responsible for such a phenomenon. It can also be concluded that it is difficult to derive the pure mechanical wear component in tribocorrosion by simply conducting a test at an arbitrary cathodic potential.

Inhibitive effect of sodium carbonate on corrosion of AZ31 magnesium alloy in NaCl solution

Magnesium is the world’s lightest structural metal, with a significant growth potential in view of the accelerating demand for light-weighting portable devices and transportation (aerospace, automotive), amongst other. The effect of carbonate ions on corrosion protection of AZ31 magnesium alloy was studied in 0.1 M NaCl solution saturated in Mg(OH)2 using Electrochemical Impedance Spectroscopy (EIS), potentiodynamic polarization measurements, hydrogen evolution tests and SEM-EDX analysis. X-ray Photoelectron Spectroscopy (XPS) was used in order to investigate the top-surface composition. The inhibitive effect of CO32− ions on corrosion of AZ31 magnesium alloy was highlighted and the underlying mechanisms discussed.

The inhibition behavior of novel ionic liquids for magnesium alloy in NaCl solution: Experimental and theoretical investigation

Three pyrazolium ionic liquids 1-n-butyl-2-hexylpyrazole bis(trifluoromethylsulfonyl)amide ([BHPz][NTf2]), 1-n-butyl-2-octylpyrazole bis(trifluoromethylsulfonyl)amide ([BOPz][NTf2]), and 1-n-butyl-2-decylpyrazole bis(trifluoromethylsulfonyl)amide ([BDePz][NTf2]) are firstly synthesized and their corrosion inhibition for AZ91D magnesium alloys in 0.05 wt% NaCl solution is investigated. The highest inhibition efficiency is 90.0% under optimal test conditions. The inhibition performance is measured by electrochemical tests, and follows the Langmuir adsorption model. The surface morphology is determined by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which testifies the formation of protective films on Mg alloy surface. The possible inhibited mechanism is proposed according to X-ray photoelectron spectroscopy (XPS) analysis and the density functional theory (DFT) calculation.

H2 generation kinetics/thermodynamics and hydrolysis mechanism of high-performance La-doped Mg-Ni alloys in NaCl solution—A large-scale and quick strategy to get hydrogen

In this work, La-doped Mg-Ni multiphase alloys were prepared by resistance melting furnace (RMF) and then modified by high-energy ball milling (HEBM). The hydrolysis H2 generation kinetics/thermodynamics of prepared alloys in NaCl solutions have been investigated with the help of nonlinear and linear fitting by Avrami-Erofeev and Arrhenius equations. Combining the microstructure information before and after hydrolysis and thermodynamics fitting results, the hydrolysis H2 generation mechanism based on nucleation & growth has been elaborated. The final H2 generation capacities of 0La, 5La, 10La and 15 La alloys are 677, 653, 641 and 770 mL·g − 1 H2 in 240 min at 291 K, respectively. While, the final H2 generation capacities of HEBM 0La, 5La, 10La and 15 La alloys are 632, 824, 611 and 653 mL·g − 1 H2 in 20 min at 291 K, respectively. The as-cast 15La alloy and HEMB 5La alloy present the best H2 production rates and final H2 production capacities, especially the HEBM 5La can rapidly achieve high H2 generation capacity (670 and 824 mL·g − 1 H2) at low temperature (291 K) within short time (5 and 20 min). The difference between the H2 generation capacities is mainly originated from the initial nucleation rate of Mg(OH)2 and the subsequent processes affected by the microstructures and phase compositions of the hydrolysis alloys. Relative low initial nucleation rate and fully growth of Mg(OH)2 nucleus are the premise of high H2 generation capacity due to the hydrolysis H2 generation process consisted by the nucleation, growth and contacting of Mg(OH)2 nucleus. To utilization H2 by designing solid state H2 generators using optimized Mg-based alloys is expected to be a feasible H2 generation strategy at the moment.

Hyperbranched molecules having multiple functional groups as effective corrosion inhibitors for Al alloys in aqueous NaCl

Hyperbranched molecules are a kind of promising materials due to their unique structures. In this work, two hyperbranched molecules (GON and GOH) are used as effective inhibitors for Al alloys in NaCl solution. Their inhibitive performances are evaluated by electrochemical measurements and surface characterization. The results indicate that inhibition performances of GON and GOH are closely related to the concentrations, influenced by the combination of steric hindrance and bonding effects. At relatively low concentrations (0.03–0.10 mM), GON displays a more pronounced ability to inhibit corrosion than GOH, owing to more anchoring functional groups. Oppositely, GOH has good inhibition performance at higher concentrations (0.50–1.00 mM). The interaction between the Al electrode and GOH results in the formation of a more condenser protective film than GON at high concentrations. In addition, the adsorption mechanism of two hyperbranched molecules is revealed by theoretical calculations.

Orange peel extracts as biodegradable corrosion inhibitor for magnesium alloy in NaCl solution: Experimental and theoretical studies

Performance of orange peel extracts (OPE) to retard the magnesium alloys corrosion is thoroughly evaluated by Electrochemical impedance spectra (EIS) and potentiodynamic polarization curves. OPE would be an effective inhibitor with the efficiency of 85.7% at very low concentration of 0.030 g L −1. The inhibition effect of selected three pure components including in OPE is much inferior or comparable with that of OPE, whereas the cost of pure compounds is too expensive to be afforded. The protective self-assembly film would be formed on the magnesium surface by immersion in OPE. Structure characterization is performed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffractometer (XRD). The adsorption of OPE on magnesium surface follows the Langmuir adsorption rule with both chemical and physical interactions. The interaction between three selected pure compounds and magnesium alloys is further calculated by density functional theory (DFT). Moreover, the possible inhibition mechanism is constructed on the basis of above results along with the FTIR measurements. The low cost and green inhibitor is explored in this work, which would replace the expensive inhibitors with the similar or better performance.

Enhancement of Anticorrosion Properties of Epoxy Based Primer Coating by Bis[[3,4-Dihydroxyphenylmethylene] carbonothioicdihydrazide] on AA2024-T3 Alloy

A corrosion inhibitor bis[[3,4-dihydroxyphenylmethylene]carbonothioicdihydrazide] (DCT) was synthesized and used to improve the corrosion resistance of an epoxy based primer coating on AA2024-T3 alloy in NaCl solution. The ability of DCT to inhibit the corrosion was evaluated by electrochemical studies. The compound exhibited an inhibition efficiency of 99%. The surfaces of the corroded specimens were characterized by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The anticorrosion nature of the substrate coated with a commercial epoxy-based primer doped with DCT was evaluated by electrochemical impedance spectroscopy and a salt spray test. The results established not only the ability of DCT to improve the anticorrosion property of the epoxy based primer coating on AA2024-T3 alloy but also a sustained corrosion protection (1000 h) of the alloy.

Effect of Solution Temperature on the Corrosion Behavior of 6061-T6 Aluminum Alloy in NaCl Solution

The influence of solution temperature on the corrosion behavior of 6061-T6 aluminum alloy in 3.5% NaCl solution was studied by electrochemical tests, weight loss method, and surface morphology analysis. The results show that the samples treated at different solution temperatures have different corrosion resistance. The anticorrosion resistance of aluminum alloys decreases first and then increases as the solution temperature increases. At 535 °C, the sample has the optimal corrosion resistance, with a slight corrosion degree, while the alloy sample treated at 555 °C shows the most severe degree of corrosion, with a large number of different sized pits and some ulcerous corrosion pits, as well the apparent intergranular corrosion. The corrosion behavior of different solid aluminum alloy samples is closely related to the microstructure. The Mg2Si precipitates act as the anode phase to protect the substrate, and a decrease in the amount of AlFeSi precipitates reduces the number of micro-galvanic corrosion cells, and the severe segregation of AlFeSi precipitates accelerates the corrosion.

A self-curing konjac glucomannan/CaCO3 coating for corrosion protection of AA5052 aluminum alloy in NaCl solution

A composite coating containing konjac glucomannan (KGM) and CaCO3 was fabricated on AA5052 alloy through a self-curing process, and its surface morphology and component were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The effect of Ca(OH)2 content on the protective property of the composite coating for aluminum alloy in 3.5 wt% NaCl solution was evaluated by electrochemical impedance spectroscopy measurements. Moreover, the inhibitory performance of the coating on the pitting corrosion of metal was examined by potentiodynamic polarization curves and atomic force microscopy (AFM). The images of scanning electron microscope show the composite coating with a thickness of 50 μm has well-defined branch-shaped structure. The FT-IR spectra confirm the successful fabrication of the polymer coating through the formation of CaCO3. The results of electrochemical impedance spectroscopy suggest that the resistance of the aluminum alloy sample coated with such protective layer is improved by six orders of magnitude, compared with the bare metal. After 60 d of immersion, the polarization curve data and AFM analysis show the pitting corrosion occurring on AA5052 surface is prevented due to the barrier property of coating.

Insight into inhibition behavior of novel ionic liquids for magnesium alloy in NaCl solution: Experimental and theoretical investigation

Three ionic liquids, decyl triphenyl phosphonium bis(trifluoromethylsulfonyl)amide ([DTP][NTf2]), tetradecyl triphenyl phosphonium bis(trifluoromethylsulfonyl)amide ([TTP][NTf2]), and octadecyl triphenyl phosphonium bis(trifluoromethylsulfonyl)amide ([OTP][NTf2]), are firstly synthesized and their corrosion inhibition for AZ31B magnesium alloys in 0.05 wt.% NaCl solution is measured by electrochemical tests. The surface morphology is determined by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which testifies the formation of protective films on Mg alloy surface. The inhibition mechanism is further elucidated by X-ray photoelectron spectroscopy (XPS), first principle calculation along with molecular dynamics (MD). Possible inhibited mechanism is proposed finally. The highest inhibition efficiency is 91.9% by addition of 0.30 mM [OTP][NTf2] in corrosive media.

Corrosion behaviour of AA2024 aluminium alloy in different tempers in NaCl solution and with the CeCl3 corrosion inhibitor

AbstractThe paper analyses the corrosion behaviour of naturally and artificially aged AA2024 alloy in NaCl solution and in the presence of an environment‐friendly corrosion inhibitor, CeCl3. On the basis of the values of polarisation resistance and corrosion current density, the corrosion resistance of the protective inhibitor film is established as well as the general corrosion resistance of this aluminium alloy. Resistance to pit formation is determined based on the difference in pitting and corrosion potentials while resistance to pit growth is determined based on the amount of charge consumed during pit growth. A scanning electron microscope is used to examine the morphology of the pits formed during the pitting corrosion testing, as well as to determine the cerium content on intermetallic particles and the matrix AA2024 alloy. The corrosion behaviour of AA2024 alloy is investigated after different test periods in NaCl solution and in the same solution with the CeCl3 inhibitor. The corrosion resistance of both tempers of AA2024 alloy is more than one order of magnitude higher in the presence of CeCl3. An explanation of the observed differences in the corrosion behaviour of the naturally and artificially aged AA2024 alloy is proposed. Different corrosion behaviour of the alloy after different test periods is also explained.

Isothermal hydrogen production behavior and kinetics of bulk eutectic Mg–Ni-based alloys in NaCl solution

To seek bulk Mg-based alloys with excellence H2 production properties, smelted eutectic Mg–Ni-based alloys are successfully prepared by metallurgical method. The phase compositions and microstructures are tested by X-ray diffraction (XRD) and scanning electron microscope (SEM). The isothermal H2 production curves of prepared alloys in 3.5 wt% NaCl solution are collected at different temperatures by drainage method. H2 production kinetics and thermodynamics are investigated in combination with the microstructures results and fitting results of hydrolysis curves by Avrami-Erofeev equation and Arrhenius equation. The production capacity for Mg-23.5 wt%Ni (Mg23.5Ni) eutectic alloy is 706 mL g−1 with 0.92 conversion yield at 303 K. When 10 wt% La added, the production capacity and yield of Mg-23.5 wt%Ni-10 wt%La (Mg23.5Ni10La) are 679 mL g−1 and 0.98, respectively. The initial rate and final capacity for H2 production of experimental Mg–Ni-based eutectic alloys improve gradually with the rising reaction temperature. The hydrolysis apparent activation energies for Mg23.5Ni and Mg23.5Ni10La alloys are 40.56 kJ/mol and 31.72 kJ/mol, respectively. The refined lamellar microstructure and the introduced La2Mg17 active phase strongly promote the H2 production process of Mg23.5Ni10La alloy. The reported results provide promising way to synthesize bulk Mg-based H2 production alloys with high yield and rapid rate by controlling the microstructure and hydrolysis reaction.

Electrochemical Behavior of Conventional and Rheo-High-Pressure Die Cast Low Silicon Aluminum Alloys in NaCl Solutions

The electrochemical behavior of a low silicon aluminum alloy cast by the conventional and rheo-high-pressure die cast processes is evaluated using polarization test and electrochemical impedance spectroscopy in 0.01 M, 0.05 M, 0.1 M, and 0.6 M sodium chloride solutions. Compared to the conventional high-pressure die cast process, rheocasting introduces some alterations in the microstructure including the presence of aluminum grains with different sizes, formed at different solidification stages. According to the results of the anodic polarization test, conventional cast and rheocast samples show similar breakdown potentials. However, the rheocast samples present enhanced oxygen reduction kinetics compared to the conventional cast sample. Based on scanning electron microscopy examinations, localized microgalvanic corrosion is the main corrosion mechanism for both alloys and it initiates at the interface of aluminum with iron-rich intermetallic particles which are located inside the eutectic regions. The corrosion further develops into the eutectic area. Although the rate of the cathodic reaction can be influenced by the semisolid microstructure, according to the results of anodic polarization and electrochemical impedance spectroscopy tests, the corrosion behavior is not meaningfully affected by the casting process.

Resistance to Pit Formation and Pit Growth for Different Tempers of AA2024 Aluminium Alloy in Presence of Benzotriazole

The paper analyses the corrosion behaviour of both naturally and artificially aged AA2024 aluminium alloy in NaCl solution in the presence of the corrosion inhibitor benzotriazole (BTA). The differences between these two aging tempers in terms of resistance to general corrosion are explained as well as the differences in terms of pit formation and pit growth. Based on the values of the polarisation resistance and the corrosion current density, the general corrosion resistance of the alloy is determined in the absence and in the presence of BTA. The resistance to pit formation and pit growth is determined on the basis of the polarisation measurements results. Scanning electron microscopy confirmed the expected differences in the appearance and size of the pits formed in naturally aged and artificially aged alloy. In the presence of the corrosion inhibitor BTA, for both aging tempers of the alloy, the corrosion resistance is significantly higher compared to the resistance in the solution without the inhibitor. The value of the polarisation resistance for both aging tempers increases over time. However, at the same time, the value of the constant phase element increases as well. An explanation for this phenomenon is provided. The calculated average value of the thickness of the adsorbed inhibitor layer on the surface of the aluminium alloy is in accordance with the inhibitor protective ability for both aging tempers.

Catalytic effect of EG and MoS 2 on hydrolysis hydrogen generation behavior of high‐energy ball‐milled Mg‐10wt.%Ni alloys in NaCl solution—A powerful strategy for superior hydrogen generation performance

In this study, the metallurgical melting Mg-10wt.%Ni (Mg10Ni) alloy is firstly modified by high-energy ball milling (HEBM) and then surface catalysts expanded graphite (EG) or MoS2 or EG-MoS2 are introduced to prepare Mg10Ni-M (M = EG, MoS2, and EG-MoS2) composites. The effects of surface catalysts on hydrolysis hydrogen generation of HEBM Mg10Ni alloy are comprehensively investigated. Their kinetics, rate-limiting steps, and apparent activation energies are investigated by fitting the hydrolysis curves at different temperatures. The results indicate that the total hydrogen generation capacities of prepared Mg10Ni-M (M = EG, MoS2, and EG-MoS2) composites are 200, 170, 674, and 720 mL·g−1 within 1 minute at 291 K. The capacity and yield of Mg10Ni are 500 mL·g−1 and 56% within 15 minutes. The surface catalysts EG or MoS2 or EG-MoS2 can distinctly elevate the initial H2 produce rate and promote the complete hydrolysis process. The highest capacity and generation yield within 15 minutes are 740.8 mL·g−1 and 91% obtained by HEBM Mg10Ni-EG-MoS2 composite at 291 K. The surface catalysis can promote high generation yield of Mg10Ni alloy in a short time.

Formation of a Convex Structure During the Counter-Rotating Electrochemical Machining of TC4 Titanium Alloy in NaCl Solution

Formation of a Convex Structure During the Counter-Rotating Electrochemical Machining of TC4 Titanium Alloy in NaCl Solution