Aluminium In Acid Solutions Research Articles

Nature of instability in flow-driven porous anodic oxide.

Self-organized porous anodic oxide films are formed by the electrochemical oxidation of reactive metal aluminum in acidic solutions in which the oxide is soluble. Recently, viscous flow models have shown using linear stability analysis that the instability results from a trade-off between the destabilizing effect of viscous flow of oxide and the stabilizing effect of oxide formation, which provides the wavelength selection mechanism for pattern formation. Anion adsorption on surface growth sites causes nonuniform compressive stress at the oxide-solution interface, which drives the flow. This anodic instability is analogous to the classical Marangoni instability induced by surface tension gradients. In this work, nature of the instability beyond the stability threshold is determined using a weakly nonlinear analysis. For the growth of well-developed pores beyond the threshold, a subcritical nature of the instability is essential. However, our weakly nonlinear analysis shows that the solutions emerging from neutral stability are supercritical in nature at all wavenumbers for the practical range of anodizing control parameters investigated. We also determine the region where the model is Hadamard stable, a necessary condition for well-posedness.

Analysis of calcination activation modified coal gangue and its acid activation mechanism

Acid activation and utilization of coal gangue is of great significance for effective treatment of bulk solid waste in the environment. However, most gangue is quite inert and requires calcination to induce acid activation. In this paper, coal gangue was calcined, and the optimal calcination temperature for activation of the coal gangue acid was explored. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry/thermal differential analysis (TG/DTG) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the crystal structures of the gangue samples formed at different calcination temperatures, which showed that increases in the amorphous content and structural degradation of the coal gangue samples occurred during calcination. The solubility of silicon and aluminum in acid solution was demonstrated with inductively coupled plasma optical emission spectroscopy (ICP‒OES). XRD and TG/DTG were used to characterize the acid activation products formed at different calcination temperatures. The results show that with the increase of calcination temperature, the compressive strength first increases and then decreases, and reached the maximum value at 650 °C; the compressive strengths at 7 d, 28 d and 90 d were 1.32 MPa, 3.22 MPa and 5.14 MPa. At 650 °C, the kaolinite in the gangue was converted into metakaolin, the aluminum-oxygen octahedra had the hydroxyl groups removed, the silicon-oxygen tetrahedra were depolymerized, the absorption bands for Si–O, Si–O–Al and Al–O bonds were broadened, the Al2p and Si2p binding energies were reduced, the splitting were increased, and more Al dissolved in the acid solution, so it has the highest acid reactivity.

The role of the oxide layer in the corrosion of aluminium in acidic solutions

AbstractThe role of the oxide layer in the corrosion of aluminium in hydrochloric, sulphuric(VI) and orthophosphoric acid is studied at pH 1. The oxide layer is stable in hydrochloric and sulphuric acids. The corrosion rate of aluminium in these solutions is 0.2 and 0.3 mm/year, respectively. The oxide layer is unstable in orthophosphoric acid and the corrosion rate is higher, 1.75 mm/year. The corrosion process is studied using scanning electron microscopy, immersion and electrochemical techniques. The mechanism of corrosion of aluminium in the orthophosphoric acid solution is proposed. It includes the adsorption of a reaction intermediate on the surface of the corroding metal and the formation of the oxide layer at anodic potentials with respect to the open‐circuit potential. It is also explained when the inductive loop appears on the electrochemical impedance spectra of aluminium corroding in orthophosphoric acid solution. The mechanism of aluminium corrosion in hydrochloric and sulphuric acid is more complex compared to orthophosphoric acid, and is not analysed in detail.

Understanding the fast formation mechanism of hard nanoporous alumina films on aluminum in acidic solutions containing nitric acid

Nanoporous alumina films formed on aluminum via anodization are widely used for scientific and technical purposes owing to their various advantageous properties, including excellent corrosion and wear resistance, good thermal and electrical insulation, and facile producibility at low cost. Herein, we report a novel approach to fabricate hard porous anodic alumina (PAA) films by adding an appropriate amount of nitric acid to sulfuric-, oxalic-, and phosphoric-acid solutions at critical high current densities. The effects of the nitric additives on the anodizing behavior, film growth mechanism, microstructure, chemical composition, film thickness, microhardness, and appearance of the PAA films formed from various solutions were systematically investigated. The addition of nitric acid enhanced the formation of alumina and resulted in fast growth rates of 196 μm/h and 166 μm/h for sulfuric- and oxalic-based solutions, respectively, while maintaining high hardness of approximately 380 and 430 HV0.1, respectively. The surface hardness of the films decreased to some extent with the increase in nitric acid concentration and/or film thickness owing to the strong corrosive nature of nitric acid during prolonged anodization, although nitrogen inclusion in anodic alumina films was not detected through X-ray photo-electron spectroscopy, which differs from the other acidic anions. In particular, the barrier layer thickness and pore intervals of PAA films increased with the nitric concentration in the aforementioned solutions, leading to a fast growth rate and high hardness inside the films.

Anticorrosive properties of Eucalyptus (Nilgiris) leaves extract on 2S grade aluminium in acid solutions

The study is on the application of Eucalyptus leaves extract (ELE) as anticorrosive properties for aluminium alloy in 0.5 M HCl by using potentiodynamic polarization (PDP), gravimetric weight loss, and Electrochemical impedance spectroscopic (EIS) methods. The corrosion inhibition characteristics of ELE on aluminium in HCl solution have been examined. This investigation showed the finest inhibition efficiencies of 95.0%, 92.0% and 89.3% that were obtained from weight loss, PDP and EIS at concentration of 0.5% ELE at 303 K respectively. As per Langmuir adsorption isotherm models, an extract of Eucalyptus leaves was adsorbed on the metal surface. The effect of the temperature on the corrosion behaviour with adding of the best concentration of ELE was studied in the temperature range 313–333 K. It was found that inhibition efficiency is independent of temperature. The negative Gibb's free energy and activation parameters of the ELE were recorded and the results indicated that the adsorption rates were spontaneous. The results obtained from PDP and EIS shows that the corrosion inhibition procedure is charge transfer controlled, and the ELE works as a mixed-type inhibitor. The findings of SEM (Scanning electron microscopy) and AFM (Atomic forcemicroscopy) studies support the adsorption inhibition mechanism. The results of all the experiments conduct are consistent. The functional groups of the ELE were identified using Fourier transform infrared (FTIR) spectroscopy.

Polyamides containing Oxadiazole ring moiety as corrosion inhibitor for Aluminium in acid solution.

Corrosion control of metals is an important activity of technical, economic, environmental, and aesthetical importance. The use of inhibitors is one of the best options for protecting metals and alloys against corrosion. This study involves the investigation of new and effective polymeric material for the application of corrosion inhibition on aluminium in the acid medium using chemical and electrochemical methods. Results obtained from weight loss and potentiodynamic and impedance methods confirm that polyamides containing oxadiazole rings in their backbone can act as effective corrosion inhibitors. The adsorption behaviour of this polymer on aluminium in 1N HCl was found to obey Langmuir adsorption isotherm. SEM studies confirmed the protective film formed on aluminium by the adsorption of Polyamides.

Synthesis and characterization of novel ionic liquids based on imidazolium for acid corrosion inhibition of aluminum: Experimental, spectral, and computational study

Three newly ionic liquids namely, 1-bnzyl-2-methyl-3-octyl-1H-imidazol-3-ium bromide, 1-bnzyl-3-decyl-2-methyl-1H-imidazol-3-ium bromide, and 1-bnzyl-3-dodecyl-2-methyl-1H-imidazol-3-ium bromide are synthesized and their chemical structures characterized via different spectra techniques (FT-IR, elemental analysis,and 1H NMR). The corrosion inhibition of newly ionic liquids was evaluated on aluminum alloy in 1 M HCl at varied exposure temperatures (298–318 K) and varied concentrations via various experimental and theoretical methods for example mass loss, electrochemical, spectral, and computational calculations. The results illustrate that these types of ionic liquids inhibit corrosion of aluminum in acid solution with maximum inhibition efficiency was reached 83.2 % at 298 K. The inhibition efficiency increases with the addition of zinc sulfate which has a synergistic impact which was reached to 92.7%. Also, the concentration of ionic liquids and the kind of cation have an impact on the obtained results. The existence of these inhibitors in the acidic solution improves the charge transfer resistance and lessens the double-layer capacitance. The Langmuir adsorption isotherm governs the adsorption of these inhibitors' molecules on the aluminum alloy surface, and they behave as mixed-type inhibitors. The outputs reveal that the computational calculations match the experimental data rather well.

Trizma as an Efficient Inhibitor for the Corrosion of Aluminium in Acid Solutions Containing Chloride Ions

Trizma as an Efficient Inhibitor for the Corrosion of Aluminium in Acid Solutions Containing Chloride Ions

Ashwagandha Extract as Green Sustainable Corrosion Inhibitor for Aluminum in Acidic Solutions

In this study, the employment of Ashwagandha extract (AE) as a green sustainable corrosion inhibitor for aluminum in one molar hydrochloric acid solutions was examined utilizing “mass loss (ML), electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) measurements”. The surface examination was analyzed utilizing atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) analysis. The effect of temperature on corrosion demeanor with adding a different dose of AE was investigated within the temperature varieties of 25-45 ºC by ML strategy. The curves of polarization reveal that AE is considered as a mixed sort inhibitor. The performance of inhibition rises with raising the AE concentration and diminished with the temperature ascending. The adsorption of the inhibitor on aluminum surface complies with the Langmuir’s adsorption isotherm and is considered as physisorption. The outcomes attained from chemical and electrochemical methods are in good accord.

Citrate and Polyvinylpyrrolidone Stabilized Silver Nanoparticles as Selective Colorimetric Sensor for Aluminum (III) Ions in Real Water Samples.

The use of silver nanoparticles stabilized with citrate and polyvinylpyrrolidone as a sensor for aluminum ions determination is proposed in this paper. These non-functionalized and specific nanoparticles provide a highly selective and sensitive detection system for aluminum in acidic solutions. The synthesized nanoparticles were characterized by transmission electron microscopy. Surface plasmon band deconvolution analysis was applied to study the interaction between silver nanoparticles and aluminum ions in solution. The interaction band in the UV-visible region was used as an analytical signal for quantitation purposes. The proposed detection system offers an effective AND wide linearity range (0.1–103 nM), specificity for Al(III) in THE presence of other metallic ions in solution, as well as high sensitivity (limit of detection = 40.5 nM). The proposed silver-nanoparticles-based sensor WAS successfully used for detecting Al(III) in real water samples.

Chromoleana odorata and Hevea brasilensis as a Green Corrosion Inhibitor for Aluminium in Acid Solution

Chromoleana odorata and Hevea brasilensis as a Green Corrosion Inhibitor for Aluminium in Acid Solution

Synthesis of baicalin derivatives as eco-friendly green corrosion inhibitors for aluminum in hydrochloric acid solution

Three baicalin derivatives named methyl ester of baicalin (BM), ethyl ester of baicalin (BE), and n-propyl ester of baicalin (BP) were synthesized in the laboratory using the traditional Chinese medicinal herb Scutellaria baicalensis Georgi as raw material. The inhibition effect of the as-synthesized baicalin derivatives was investigated as eco-friendly green inhibitors on the corrosion of aluminum in 1.0M HCl solution by weight loss and various electrochemical techniques. Results show that the baicalin derivatives exhibit excellent performance as inhibitors for aluminum corrosion. The synthesized baicalin derivatives suppress both the anodic and cathodic process and the compounds behave as mixed-type corrosion inhibitors for aluminum in HCl solution. Also, results obtained indicate that compound BM is the best inhibitor and the effectiveness of these inhibitors decreases in the order of BM>BE>BP. The maximum inhibition efficiency obtained at 25°C using BM=0.9 g/l was ∼95%. The interpretation of the inhibition due to adsorption of the compounds on the aluminum surface is according to Langmuir adsorption isotherm. The free energy of adsorption for inhibition process was determined on the basis of Langmuir adsorption isotherm. Surface analyses were performed to establish the mechanism of corrosion inhibition of aluminum in acidic solution. The formation of the adsorbed baicalin-Al3+ complex on the metal surface led to slow down the corrosion rate of aluminum and improvement of the inhibition process.

Nanostructured Porous Aluminum Oxide: Production, Properties

The results of an investigation into the production of porous aluminum oxide, which is a typical self-organized material, by anodic oxidation of aluminum in acid solutions are presented. The functional dependences of the impact of the formation conditions on the structural parameters of porous anodic aluminum oxide, including pore diameter and oxide-cell size, are studied.

Alternating Current Phosphoric Acid Etching of Aluminium

Alkaline etching is a common pretreatment process for aluminium alloys before anodising or application of organic coating. Removal of the mill-finish surface layer is performed by a simple dipping process, which also gives the matt finish normally required for aesthetic appearance before conventional anodising. Major disadvantage of alkaline treatment is the surface enrichment of the alloying and trace elements more noble than the aluminium substrate by dealloying. This may reduce corrosion resistance and deteriorate the optical properties of the surface. The purpose of this work is to investigate fluoride-free acid etching for aluminium alloys as an alternative to alkaline etching to prevent or reduce heavy metal enrichment, while achieving matt appearance. Alternating current is applied to increase the rate of etching as the dissolution rate of aluminium in acid solutions is slower than in alkaline solutions. The principle is based on anodic oxidation of the heavy metal components, as well as aluminium, during the anodic cycle and removal of the corrosion products and concentration gradients by hydrogen evolution during the cathodic cycle. The materials used for this study were hot-rolled aluminium alloy AA3105 (Si 0.3%, Fe 0.6%, Cu 0.1%, Mn 0.7%, Mg 0.3%) and extrusion AA6060 (Si 0.4%, Fe 0.2%, Cu 0.01%, Mn 0.02%, Mg 0.5%). Phosphoric acid was used as the etching electrolyte. Consumption of aluminium was calculated from weight loss. Appearance was analysed visually and by gloss measurements. SEM was used to study surface microstructure and morphology. Aluminium oxidation rate increased with increasing temperature, current density, electrolyte concentration and etching time. Intermetallic Al-Mn-Fe-Si particles were selectively and rapidly removed by 1 min etching at 80⁰C. In contrast, particles were exposed and remained on the surface by alkaline etching. Matt appearance without visible defects was achieved after 10 min etching at 80⁰C. Presence of phosphorus in thin oxide film formed was determined by glow discharge optical emission spectroscopy (GD-OES). Advantages foreseen of acid-based AC pretreatment over alkaline dip processes in practice are suitability for in-line coil processing, superfluity of the desmutting step, low gloss achievable with reduced metal loss, improved corrosion resistance and adhesion properties. Acknowledgements This work was supported by Hydro Aluminium and The Research Council of Norway.

The Effect of Inhibitor on the Corrosion of Aluminium in Acidic Solutions

The Effect of Inhibitor on the Corrosion of Aluminium in Acidic Solutions

Organic corrosion inhibitors for aluminium and its alloys in acid solutions: a review

Corrosion inhibition of aluminium in acidic solutions using different organic compounds.

Nionic Effect on the Acidic Corrosion of Aluminum and its Inhibition by Lupine Extract

Corrosion behavior of aluminum in 0.1 M HCl, 0.1 M HClO 4 and 0.05 M H 2SO 4 solutions was studied using potentiodynamic polariz ation and electrochemical impedance spectroscopy (EIS) techniques. The results showed that the rate of corrosion of aluminum was arranged in the order: HCl > HClO 4 > H 2SO 4. Lupine extract is an effective green inhibitor for the corrosion of alum inum in acidic solutions. The inhibition efficiency of the extract was found to i ncrease with increasing the concentration of the extract. The obtained results showed that the lupine extract is effective in the order HClO 4 > HCl > H 2SO 4. Theoretical fitting of the corrosion data to the Kinetic-thermodynamic model was tested to clari fy the nature of adsorption.

Role of Oxide Stress in the Initiation of Pores during Anodic Oxidation of Aluminum in Acid Solutions

Porous anodic oxide films are produced when reactive metals such as Al and Ti are electrochemically oxidized in baths that dissolve the oxide. Much research in porous oxide based devices has been stimulated by the self-organized hexagonally ordered pore arrays found for certain anodizing conditions.1 However, the process of pore formation and self-ordering is not yet understood. Morphology evolution accompanying pore initiation has been characterized during, for example, constant current anodizing of Al in 0.4 M H3PO4.2 A morphological instability of the initially planar barrier oxide occurs at 10-20 nm thickness, resulting in a disordered pattern of small pores spaced at about 20 nm. The barrier oxide thickness then continues to increase up to about 150 nm, at which the self-ordered pattern of pores spaced at 230 nm initiates. The initial instability at 10-20 nm is apparently controlled by the interplay of dissolution and electrical migration.3 A tracer study recently found evidence that plastic flow of oxide is involved in the transition to the self-ordered pore pattern.4 It had been previously shown that stress builds up at a constant rate during the regime of barrier oxide growth, suggesting elastic loading of the anodic film.5,6 The rationale for the transition from elastic to plastic oxide behavior are yet unclear.The present work related the evolution of the stress distribution in the barrier oxide layer to the initiation of the self-organized pore array. Al samples were anodized at constant current density in 0.4 M H3PO4. Through-thickness profiles of the in-plane stress in the oxide were revealed for the first time, by in situ monitoring of stress change during open circuit dissolution following anodizing.7 Oxide morphology evolution during anodizing was statistically characterized by Fourier transformation of SEM images.SEM images showed that the morphological instability initiated at an oxide thickness of 20 nm, and produced a stable surface roughness pattern with a length scale of 20 nm. Prior to the instability, stress measurements showed that compressive stress in the oxide was evenly dispersed through the oxide thickness. However, after the instability, the stress profile became concentrated within a layer of about 20 nm thickness adjacent to the oxide-solution interface. At greater depths, the oxide was stress-free, revealing that the compressive stress is generated by absorption of oxygen ions (and possibly phosphate ions) at the solution interface. With increasing barrier oxide thickness, the stress level within the stress-accumulating layer became increasingly compressive. This behavior continued until the moment of self-ordered pore initiation, when both the barrier layer thickness and the integrated oxide stress rapidly decreased to steady-state values. Both the morphology change and stress transient can be attributed to the relaxation of elastic stress due to the onset of plastic flow. Therefore, the stress measurements reveal that key role of oxide flow in pore initiation, in agreement with the aforementioned tracer study.4 The present experiments suggest that the self-ordered pore array initiates due to plastic yielding of the oxide. The compressive stress buildup to the yield stress is possible because of the initial morphological instability, which seems to establish a layer of constant thickness within which compressive stress accumulates during barrier oxide growth. Without this layer, stress would be dispersed through the thickness of the growing film, and the stress level would not change during as the barrier oxide thickness increased. The reason for localized stress accumulation will be explored using a mathematical model for stress evolution during barrier oxide growth.8 AcknowledgmentSupport was provided by the National Science Foundation CMMI-100748.

Factors affecting the corrosion behaviour of aluminium in acid solutions. II. Inorganic additives as corrosion inhibitors for Al in HCl solutions

CrO42−, WO42− and HPO42− ions affect on the corrosion behaviour of Al in 2M HCl. The inhibition efficiencies of the additives depend on their type and increase with increasing concentration. Oxide film destruction and/or repair follow a direct logarithmic law. The inhibitive action of these anions is discussed in terms of competitive adsorption with Cl− ions on the electrode surface followed by a reduction mechanism to form metal oxides. The calculated values of ΔG°ads of the inhibition process reveal a physical adsorption of the inhibitors. The inhibition efficiency is found to decrease in the order: CrO42−>WO42−>HPO42−.

Solanum surrattence as Potential Corrosion Inhibitor

Developping chip and ecofriendlly corrosion inhibitors can replace toxic chemicals which are currently used in industries. Plant extract of Solanum surrattence in acetone, petroleum ether, and methanol has been tasted using mass loss and thermometric measurements for corrosion of aluminium in acid solutions. The plant extract of Solanum surrattence is a good corrosion inhibitor for aluminium. The inhibition efficiency depends upon the concentration of inhibitors, it inhibits the metal of 97.60% at its maximum value. This inhibitor shows efficiency at 25°C. At higher temperature the inhibition efficiency decreases. These types of inhibitors can be used to replace the toxic chemicals which are currently used in industries. We find out cheap and ecofriendlly corrosion inhibitors which can be used by acid, petrochemical, and chemical industries.