Aluminum In Alkaline Solution Research Articles

Influence of non-stationary electric current on dissolution оf metals in aqueous solutions of alkali

Non-stationary effects can be widely used as an intensifying factor in technological processes and as a tool for studying chemical systems. Studies of energy effects on structural transformations in liquid systems can make it possible to significantly intensify many chemical and metallurgical processes. We have studied the solubility of aluminum, iron and molybdenum in alkaline solutions under the influence of alternating electric current. A two-electrode cell was used. The electrodes were made from dissolved metal. The frequency of the electric current varied from 20 to 200,000 Hz. In the process of dissolving aluminum in an alkaline solution at the same current frequency and alkali concentration, the mass loss of the aluminum sample increases with increasing current strength up to 0.042-0.044 g. A further increase of current practically blocks the dissolution of aluminum - the change in mass was 0.005-0.007 g of Al. Increasing the alkali concentration to 5.7% KOH significantly reduces the dissolution of aluminum, the weight loss is 0.009 g. The entire surface of the electrodes is covered with a film after 6 hours of dissolution. An analysis of the phases on the aluminum surface showed that the film is a phase based on potassium. The thickness of the potassium film varies depending on the depth of immersion of the electrodes in the solution and on the time of the experiment. The structure and composition of potassium and aluminum compounds could not be established.

Electrochemical and computational estimations of cephalosporin drugs as eco-friendly and efficient corrosion inhibitors for aluminum in alkaline solution

In this study, the anionic state of Ceftriaxone sodium (Cefx) and Ceftazidime (Cefz) medication corrosion inhibition capabilities for Al in 0.1 M NaOH solution are explored using various electrochemical analyses. Furthermore, the morphological structure and surface chemical composition of the impact of these drugs on the Al substrate in NaOH are investigated. For the prediction and analysis of interactions between molecule structure and inhibition efficiency, quantum chemical calculations (QC), Monte Carlo simulations (MC), and molecular dynamics (MD) simulations (MD) are performed. The electrochemical findings reveal that the inhibitory effectiveness increases with increasing drug concentrations and declines with rising temperature, reaching a maximum value of 78.4% for 300 ppm Cefx while 59.5% for 300 ppm Cefz at 293 K, implying that Cefx outperforms for Cefz. In addition, the studied drugs act as cathodic inhibitors, and their adsorption is spontaneous and mixed type adsorption in its nature that obeys Freundlich isotherm for Cefz while Temkin isotherm is the best-fitted one for Cefx. Surface analysis and wettability measurements imply that Cefx and Cefz shield the Al against corrosion by surface adsorption and generating a protective hydrophobic film. Thermodynamic activation parameters in the absence and presence of 300 ppm of the studied drugs are calculated and discussed. The energies of the border molecular orbitals and computed molecular parameters for the investigated drugs revealed that anionic Cefx is more readily adsorbed on the Al surface than Cefz. This finding is validated further using MC and MD simulations. Overall, the proposed cephalosporin drugs delivered a cost-effective and facile approach for boosting the efficiency of corrosion inhibitors for Al under aggressive conditions.

Coupling of cathodic aluminum dissolution and anodic oxidation process for simultaneous removal of phosphate and ammonia in wastewaters

Removal of excessive nutrients (N and P) is one of the most concerned issues for wastewater treatment. This study presents a paired electrolytic system consisting of Al cathode and RuO2/Ti anode for the simultaneous removal of phosphate and ammonia in wastewaters. The comparative study on the dissolving behaviors of Al cathode and Al anode showed that Al cathode could achieve a continuous and stable dissolution of aluminum, thereby forming flocs and small amounts of water soluble aluminum species for decontamination. The electrogenerated OH– in the vicinity of cathode raised the local alkalinity and caused the chemical dissolution of aluminum. According to the experiment of non-electrolytic dissolution of aluminum in alkaline solution, the local pH resulting in the cathodic dissolution of Al was estimated. The paired electrolytic system showed the capability to simultaneously remove ammonia and phosphate in simulated wastewater, and the pH neutralizing effect in association with the formation of Al species could promote the electrochemical oxidation of ammonia. When the paired electrolytic system was applied to the treatment of landfill leachate, 96.9% of ammonia nitrogen, 87.4% of total phosphorous and 89.9% of COD could be eliminated after three hours of electrolysis at 80 mA/cm2. The results shown in study reveal that the dissolution process of Al cathode enables a convenient control on the dissolving-out amounts of aluminum via regulating the applied current density, and the paired electrolytic system can be developed as an energy-efficient electrochemical wastewater treating method.

Evaluation of the Modified Extracted Lignin from Wheat Straw as Corrosion Inhibitors for Aluminum in Alkaline Solution

Evaluation of the Modified Extracted Lignin from Wheat Straw as Corrosion Inhibitors for Aluminum in Alkaline Solution

Inhibition of corrosion of aluminum in alkaline solution by a novel azo-schiff base: Experiment and theory

The inhibition effect of a Schiff base with several functional groups on the corrosion of aluminum in alkaline solution is studied by experimental techniques and density function theory (DFT) calculations. The Schiff base are characterized by 1HNMR, 13CNMR, FT-IR, and CHN elemental analysis. In addition, different electrochemical and corrosion techniques such as weight loss, tafel polarization, electrochemical impedance spectroscopy (EIS) and optical microscopy images are performed to analyze the inhibiting performances. In the Tafel measurements the cathodic Tafel slopes values incurred small changes with increasing the inhibitor concentration, which revealed that the inhibitor was adsorbed on the aluminum surface. The inhibition efficiencies are calculated from weight loss measurement and electrochemical tests. The adsorption of the inhibitor onto the aluminum surface follows the Langmuir adsorption isotherm with the free adsorption energy of −8.66 kJ mol−1. The calculated adsorption energies and the amount of charge transfer obtained by DFT calculation revealed that corrosion inhibition effectively occurs with chemisorption, where new NAl bonds are formed between of N atoms in azo (–NN–) group and Al surface atoms, which is confirmed from ab initio molecular dynamics (AIMD) simulation.

Influences of L-Cysteine/Zinc Oxide Additive on the Electrochemical Behavior of Pure Aluminum in Alkaline Solution

Severe self-corrosion is the main barrier preventing the application of aluminum as an anode material in alkaline air battery. In this work, a hybrid organic/inorganic inhibitor based on L-Cysteine/zinc oxide was tested to see if its addition to alkaline electrolyte can reduce self-corrosion of a commercial 1060 pure aluminum. Results obtained have shown that self-corrosion of pure aluminum is significantly restrained by the L-Cysteine/ZnO hybrid inhibitor without affecting its discharge performance. An interaction between ZnO and L-Cysteine leads to formation of a dense layer on pure aluminum surface. In both NaOH + ZnO and NaOH + L-Cysteine + ZnO solutions, the reaction mechanism is mainly controlled by diffusion of zincate ions. By using the L-Cysteine/ZnO hybrid inhibitor, cheap commercial 1060 pure aluminum can replace expensive 5N5 super-pure aluminum to achieve a comparable performance. This has been demonstrated in this study by comparing the battery based on commercial 1060 pure aluminum with the L-Cysteine/ZnO inhibitor and the battery made of 5N5 super-pure aluminum with 4 M NaOH solution.

Corrosion behaviour of aluminium under simulated environmental conditions of low-level waste

ABSTRACTIn Japan, low-level radioactive waste including aluminium alloys is generated from nuclear power plants. It is well known that aluminium reacts with both alkaline cement and water, generating hydrogen gas. For the safe management of radioactive waste disposal facilities, it is necessary to evaluate corrosion and hydrogen generation behaviours of aluminium corresponding to changing environmental conditions. In the present study, the corrosion behaviour of aluminium in alkaline solutions at 15 °C was evaluated.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Film dissolution kinetics of aluminium at precisely adjusted pH‐values

This work focuses on the corrosion of aluminium in alkaline solution particularly at pH 11.0. The pH value plays a key role in corrosion processes. In a certain pH range, either the metal dissolves or protective films may be formed. For performing electrochemical measurements at a precisely adjusted pH value a setup, the so called ‘impedance titrator’ is used, that allows adjusting and controlling of pH value very precisely, while characterising the film properties. Electrochemical impedance spectroscopy is performed to investigate the formation of corrosion products. By keeping the pH at a constant value and simultaneously offering the system a constant hydroxide concentration, film formation takes place under defined conditions and a full kinetic characterisation becomes possible. This special system is required as the behaviour of aluminium in alkaline solution is quite complex and a various number of competing reactions like oxide film formation and dissolution occur.

Corrosion inhibition performance of different bark extracts on aluminium in alkaline solution

The present work shows the effect of stem bark extracts of three trees namely Moringa oleifera (MO), Terminalia arjuna (TA) and Mangifera indica (MI) on the corrosion behaviour of Aluminium Alloy (AA) in 1M NaOH. The inhibition performance was studied by using gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. Among these extracts, MO exhibited the maximum inhibition efficiency η (%) of 85.3% at 0.6g/L at 303K. Polarization measurement showed that all the examined extracts are of mixed-type inhibitors. Langmuir’s adsorption isotherm was found to be best fit. Morphology of the surface was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) which confirmed the existence of a protective film of inhibitor molecule on AA surface.

Aromatic Carboxylic Acids as Corrosion Inhibitors for Aluminium in Alkaline Solution

Aromatic Carboxylic Acids as Corrosion Inhibitors for Aluminium in Alkaline Solution

Coupled Tensile Stress Increases and Topography Evolution during Aluminum Corrosion

Embrittlement of high-strength Al alloys resulting from water exposures thought to be caused by absorption of hydrogen produced by corrosion.1 Studies of Al dissolution processes indicate that corrosion itself produces large concentrations of subsurface hydrogen and defects, which may be relevant to degradation mechanisms. Hebert and coworkers detected extensive subsurface hydride formation during alkaline corrosion of Al, suggesting high hydrogen concentrations near the corroding surface.2 Studies of alkaline aluminum dissolution by electron microscopy and positron annihilation spectroscopy reveal large numbers of subsurface nanoscale voids which suggest condensation of near-surface vacancies produced during dissolution.3 Measurements of stress changes accompanying corrosion can detect defect formation, along with other microstructural changes relevant to degradation. Here we report in situ stress measurements during corrosion of 99.998% purity aluminum in alkaline solutions. The experiments utilized a new technique, phase-shifting curvature interferometry, the high curvature resolution of which enables measurement of corrosion-induced stress on bulk aluminum sheet and foils, and extension of the period of stress measurement to tens of minutes in order to capture the full evolution of stress transients during dissolution.4 Topographic changes were characterized quantitatively by Fourier transform analysis of scanning electron microscope (SEM) images, to identify length scales of the ridge-scallop surface pattern produced by dissolution. Stress measurements during dissolution in NaOH solutions revealed large reproducible tensile force increases (in-plane stress integrated through thickness) that scale directly with the sample yield stress. This is apparently the first indication of near-surface plastic deformation directly induced by corrosion. The force increases to a steady state reached after around 10 min. Close agreement of force transients for as-received and electropolished sheet samples demonstrate that stress is not influenced by near-surface microstructure. Steady-state force levels are found to increase with NaOH concentration. The force transients can be interpreted in terms of growth of a surface-adjacent plastic layer, within which the metal is at the yield stress. The thickness of this plastic layer can be approximated as the ratio of the measured force per sample width to the yield stress. Tensile force within the plastic layer is proposed to originate from the lattice contraction due to metal vacancies injected by dissolution.5 According to this mechanism, plastic layer growth should be governed by vacancy diffusion. Using a one-dimensional model for vacancy diffusion, closely comparable independent estimates of the vacancy diffusivity values are obtained from the measured steady-state force and time. These estimates are on the same magnitude as the vacancy diffusivity extrapolated from high-temperature measurements, 4 x 10-16 m2/s. Thus, the force measurements seem to be quantitatively consistent with the introduction of tensile stress by continuous vacancy formation at the dissolving surface. Vacancy injection can be rationalized by the high surface overpotential present during alkaline Al dissolution. SEM images reveal the expected surface pattern of concave scallops surrounded by convex ridges. The characteristic scallop width increases to a steady-state during dissolution, following nearly the same trajectory as that of the measured tensile force. Indeed, a universal scaling factor of 120 MPa was found to relate force to scallop diameter, implying that the plastic layer thickness and mean scallop radius remain nearly the same during dissolution. Since nearly all the hydride particles and voids observed to form during dissolution are located at ridges,2,3 we propose that diffusing hydrogen and vacancies aggregate on ridges to produce immobile hydride particles and voids, that are then removed by metal dissolution. The scaling of force to scallop diameter implies that length scale for diffusion toward the sample bulk, governing the injection rate of hydrogen and vacancies, must remain comparable to the length scale for lateral diffusion to ridges, which controls the removal rate. The present results suggest strong enhancement of diffusion by vacancies near corroding surfaces, which may be relevant to crack propagation processes. ACKNOWLEDGMENT This work was supported by the National Science Foundation through NSF-CMMI-100748. REFERENCES 1. J. R. Scully, G. A Young, S. W. Smith, in Gaseous Embrittlement of Materials in Energy Technologies, p. 707, R. P. Gangloff and B. P. Somerday, Eds.., Woodhead, Oxford (2012). 2. S. Adhikari, J. J. Lee, K. R. Hebert, J. Electrochem. Soc., 155, C16 (2008). 3. S. Adhikari, K. R. Hebert, L. S. Chumbley, H. Chen, Y. C. Jean, A. C. Geiculescu, Electrochim. Acta, 55, 6093 (2010). 4. O. O. Capraz, P. Shrotriya, K. R. Hebert, J. Electrochem. Soc., 160, D501 (2013). 5. H. K. Birnbaum et al., J. Alloys Compd., 253-254, 260 (1997).

Aluminum Corrosion Mitigation in Alkaline Electrolytes By Hybrid Inorganic/Organic Inhibitor System for Power Sources Applications

The changing and expanding needs in the energy market, ranging from power grid energy storage system to portable power sources have necessitated the development of efficient, inexpensive, and high performance battery systems to better deal with the challenges posed by the nascent green economy and non-oil based transport system. One of the promising avenues for achieving these goals is the development of aluminum battery systems based on aluminum and aluminum alloys as anodes. The main advantages presented by this system are rather low equivalent weight of the aluminum, its high natural abundance in the Earth’s crust, its low price, and its safety characteristics; also, it is substantial that aluminum and its byproducts are non-toxic and environmentally friendly. Using aluminum for these applications requires overcoming various obstacles when using different electrolyte solutions. When using aluminum in alkaline based systems the corrosion rate is very high therefore, blemishes its use in alkaline based batteries. High parasitic corrosion rate impairs the functionality of the battery due to capacity lost, dangerous hydrogen generation and significantly shorten its shelf life. Although aluminum alloys can reduce parasitic corrosion, they are frequently complex and rather expensive materials. A promising solution to the undesired corrosion is to use inhibitors which mitigate self-corrosion. Different types of inhibitors are available for use at this time, but none of them mitigate the corrosion of aluminum in alkaline solution to the extent of commercialization of a battery system. In this work, an investigation was performed on the effect of a hybrid organic\\inorganic inhibitor, poly(ethylene glycol) di-acid (PEG di-acid) and zinc oxide (ZnO), in a 5M KOH solution. The inhibitors behavior on a pure aluminum was studied electrochemically, microscopically, crystallographically, and element analysis tests were performed. Moreover, the performance of aluminum air cells with alkaline solutions utilizing the hybrid inhibition approach was evaluated by galvanostatic measurements (discharge). The results of our study clearly showed that there is a distinct and strong relation between the mitigation of the corrosion to the presence and concentration of both PEG di-acid and ZnO in the solution.  It was found that with the use of hybrid inhibition approach more than one order of magnitude redaction in corrosion currents and double the capacity of aluminum-air battery were achieved. Figure 1

Electro-corrosion machining of aluminum in alkaline solution and passivated mechanism

Aluminum mandrel was electrolyzed in 1 mol/L sodium hydroxide solution using the electrolytic corrosion device. The relationship between voltage and current was got by changing the voltage (4-28 V). The surface of aluminum was absolutely passivated when the voltage was higher than 28 V. Activation energy was obtained from data fitted by changing the electrolyte temperature (20-35 ℃). Images of surface passivation samples and non-passivated sample were got from SEM. Non-passivated and passivated samples were analyzed and characterized by XRD. The main component of surface passivation layer was bayerite. Surface reaction process and passivated mechanism were inferred from the main component of passivation product.

Electrochemical Behaviors of Different Gradesof Pure Aluminum in Alkaline Solution

Effects of impurity (Fe, Si, Cu), temperature and Na2SnO3 on anodic behaviors of various grades of pure aluminum namely Al-1(99.999%),Al-2(99.99%),Al-3(99.82%) and Al-4(99.5%) in 4mol/L KOH solution have been examined by studying corrosion rate, polarization , open circuit potential (OCP, or Eocp), discharge performance and transfer resistance values (Rt) of EIS. The results indicate that aluminum has higher activation and more severe corrosion with the temperature increase. When impurities (Fe, Si, Cu) content increases, aluminum has higher corrosion and achieving stationary open current potential (OCP) needs longer time. However, Al-3 has lower polarization and higher current density(400mA/cm2,at 1.224V) than others at 50 °C. Meanwhile, for Al-3, the stationary OCP is about 120 mV more negative at 50 °C than at 25 °C. In order to achieve the stationary OCPs and avoid the appearance of tin oxidation peak, 20min is suitable soaking time for Al in 5mmol/LNa2SnO3 +4mol/LKOH solution. The optimal electrochemical behaviors of Al including corrosion-resistance, activation , OCP and shorter delay time of electrode potential, have been achieved by adding 5mmol/L SnO32+ into 4mol/LKOH solution.

A thermodynamic model for silica and aluminum in alkaline solutions with high ionic strength at elevated temperatures up to 100  C: Applications to zeolites

In this study, a thermodynamic model for silica and aluminum in high ionic strength solutions at elevated temperatures up to 100 °C is constructed. Pitzer equations are utilized for the thermodynamic model construction. This model is valid up to ionic strengths of ~24 molal (m) in NaOH solutions with silicate concentrations up to ~1.5 m. The speciation of silica (including monomers and polymers) and aluminum at elevated temperatures is taken into account. Also, the equilibrium constants for silicic acid and its polymer species (H4SiO4, H5Si2O7- , H4Si2O72-, and H5Si3O73-) at elevated temperatures up to 100 °C, are obtained based on theoretical calculations. Using this thermodynamic model, thermodynamic properties, including equilibrium constants, and respective reaction enthalpies are obtained for sodium silicates, zeolite A, and the amorphous form of zeolite A, based on solubility experiments at elevated temperatures. The equilibrium constants for zeolite A and amorphous precursor of zeolite A regarding the following reactions up to 100 °C,

Piper longum extract as green corrosion inhibitor for aluminium in NaOH solution

The inhibiting action of Piper longum seed extracts was investigated as the corrosion inhibitors of aluminium in 1M NaOH solution using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) methods, and weight loss measurements. The results revealed that P. longum extract was an effective inhibitor, and the inhibition efficiencies obtained from polarization and weight loss experiments were in good agreement. Using the potentiodynamic polarization technique, the extract was proving to have a mixed-type character for aluminium in alkaline solution by suppressing both anodic and cathodic reactions on the metal surface. The adsorption isotherm model was determined according to fitted results obtained from the weight loss experiments performed on the aluminium specimen in 1M NaOH solution at 308K. Thermodynamic parameters such as activation energy and free energy of adsorption were calculated and given in kJmg−1.

Modeling electrochemical and metal-phase processes during alkaline aluminum corrosion

In stress corrosion cracking, the chemical pathways are not yet well-understood by which corrosion produces metal-phase defects responsible for degradation. Open-circuit dissolution of aluminum in alkaline solutions was investigated using a modeling approach, focusing on both electrochemical reactions and metal-phase processes. Pathways were identified leading to corrosion-induced tensile stress and formation of hydride, both of which can influence metal degradation processes. The model was based on the formation of vacancy–hydrogen defects during metal dissolution, and their subsequent aggregation in the metal to form hydride. Calculations successfully explained several transient measurements reported during dissolution, namely formation of subsurface voids and hydride, as well as open-circuit potential and stress.

Electro- and Electroless Deposition of Ni/SiC and Co/SiC Composite Coatings on Aluminum

Aluminum and its alloys characterize usually poor superficial properties. To improve hardness and wear resistance, aluminum base materials are covered by protective layers. Deposition of metallic coatings on aluminum is accompanied by some difficulties due to tenacious oxide layer present on the substrate surface. Hence, some additional stages are needed to assure good adhesion of the coating to the substrate. In many cases, electrodeposition and electroless methods are competitive for providing deposits with ceramic particles uniformly incorporated within the metal layer. The most extensive studies were carried out on deposition of Ni/SiC composites, but no attempts on Co/SiC coatings deposition on aluminum have been performed. Experiments presented were conducted to develop simply methods for deposition of Ni/SiC and Co/SiC composite coatings on aluminum substrate. The consecutive stages of the hydrometallurgical route were: zincating of aluminum in alkaline solutions, electroless nickel (cobalt) deposition and electrodeposition or electroless deposition of the composite coating. The influence of deposition time and composition of the baths on thickness and composition of the deposits was studied. Microstructure and microhardness of as-plated individual layers were also determined.

The effects of Phyllanthus amarus extract on corrosion and kinetics of corrosion process of aluminum in alkaline solution

The effect of the extract of Phyllanthus amarus leaves on the corrosion of aluminum in 2 M NaOH solution was studied using chemical technique. The extract acts as corrosion inhibitor, with 76% efficiency at the highest concentration in the alkaline environment and the inhibition efficiency increased with increasing concentration of the extract. The adsorption of the inhibitor on aluminum surface was in accordance with the Langmuir adsorption isotherm. A zero-order kinetics relationship with respect to aluminum was obtained with and without the extract from the kinetics treatment of the data.

Potential of aqueous extract of Hibiscus sabdariffa leaves for inhibiting the corrosion of aluminum in alkaline solutions

Chemical (HE and WL) and electrochemical (PDP and EIS) measurements were applied to evaluate the potential of aqueous extract of Hibiscus sabdariffa leaves (AEHSL) for inhibiting the corrosion of Al in 0.5 M NaOH. It was found that the inhibition efficiency increases with the increase of AEHSL concentration. Electrochemical measurements revealed that AEHSL acts as a mixed-type inhibitor with inhibition category that belongs to geometric blocking. Adsorption of inhibitor species was found to follow Langmuir and Dubinin–Radushkevich isotherm models and the ability of AEHSL species to be adsorbed physically on the Al surface was illustrated by Dubinin–Radushkevich isotherm parameters. The data obtained from chemical and electrochemical measurements are in reasonably good agreement. Physical adsorption mechanism of AEHSl species on Al surface in 0.5 M NaOH becomes clear cut by following the trend of inhibitor adsorption with solution temperature. Good correlation between AEHSL water-soluble constituents and the suggested physical adsorption mechanism was obtained. Moreover, at a certain concentration of AEHSL (1.00 g L−1), the Al surface coverage increases with the increase of NaOH concentration up to 0.5 M after which limited decrease was obtained with further increase in NaOH concentration.