Aluminium In Acid Solutions Research Articles

Factors affecting the corrosion behaviour of aluminium in acid solutions. I. Nitrogen and/or sulphur-containing organic compounds as corrosion inhibitors for Al in HCl solutions

The corrosion behaviour of Al in 2M HCl solution in the absence and presence of phenylhydrazine, urea, thiourea, N-allylthiourea, and thiosemicarbazide is investigated using different chemical and electrochemical techniques. The inhibition efficiencies of these compounds increase with increasing their concentration and molecular weights. The inhibitive action of these compounds is discussed in terms of blocking the electrode surface by adsorption of the inhibitor molecules according to Langmuir isotherm. The thermodynamic parameters Kads and ΔGads° are calculated and discussed. The values of ΔGads° reveal strong physisorption of the inhibitors on the metal surface.

Corrosion Inhibition of Aluminium in Acid Media By Citrullus Colocynthis Extract

Inhibition of corrosion of aluminium in acid solution by methanol extract of Citrullus colocynthis plant has been studied using mass loss and thermometric measurements. It has been found that the plant extract act as a good corrosion inhibitor for aluminium in all concentrations of sulphuric and hydrochloric acid solution. The inhibition action depends on the concentration of acid and inhibitor. Results for mass loss and thermometric measurement indicate that inhibition efficiency increase with increasing inhibitor concentration. The inhibition action of the plant extract is discussed in view of Langmuir adsorption isotherm. It has been observed that the adsorption of the extract on aluminium surface is a spontaneous process. The plant extract provides a good protection to aluminium against corrosion.

Corrosion inhibition of aluminium in acid solutions by some imidazoline derivatives

2-Pentadecyl-1,3-imidazoline (PDI), 2-Undecyl-1,3-imidazoline (UDI), 2-Heptadecyl-1,3-imidazoline (HDI), 2-Nonyl-1,3-imidazoline (NI) were synthesized and characterized by FT-IR and NMR Studies. The corrosion inhibition properties of these compounds on aluminium in 1 M HCl and 0.5 M H2SO4 were investigated by weight loss, potentiodynamic polarization, electrochemical impedance and scanning electron microscopic techniques. The weight loss study showed that the inhibition efficiency increases with increase in the concentration of the inhibitor and was found to be inversely related to time and temperature while it shows no significant change with increase in acid concentration. The effectiveness of these inhibitors were in the order of UDI > NI > PDI > HDI .The values of activation energy, free energy of adsorption, heat of adsorption, enthalpy of activation and entropy of activation were also calculated to elaborate the mechanism of corrosion inhibition. The adsorption of these compounds on aluminium surface follows the Langmuir adsorption isotherm. The potentiodynamic polarization data show that the compounds studied are mixed type inhibitors. Electrochemical impedance was used to investigate the mechanism of corrosion inhibition. The surface characteristics of inhibited and uninhibited metal samples were investigated by scanning electron microscopy (SEM).

Electrochemical corrosion behaviour of microcrystalline aluminium in acidic solutions

The electrochemical corrosion behaviour of microcrystalline pure aluminium coating, fabricated by a magnetron sputtering technique, has been investigated in both 0.5 mol/l NaCl and 0.5 mol/l Na 2SO 4 acidic (pH = 2) aqueous solutions. The corrosion resistance of the microcrystalline Al coating has deteriorated more compared with that of the cast pure Al in Na 2SO 4 acidic solution. However, its oxide film has a higher pitting resistance in the NaCl acidic solution. Chloride ions play a big role in the formation of the oxide film on the microcrystalline Al coating. The higher pitting resistance was attributed to the more acidic isoelectric point which the oxide film achieved.

Reductive Leaching of Chalcopyrite by Aluminum

The reductive leaching of chalcopyrite to chalcocite was achieved by contact with metallic aluminum in acidic solutions at near ambient temperatures. It was shown that increased aluminum surface area, temperature and chloride concentrations lead to larger reduction velocities and aluminum consumption. The controlling mechanism appears to be related to hydrogen generation.

Dependence of labradorite dissolution kinetics on CO 2(aq), Al (aq), and temperature

Labradorite (Ca 0.6Na 0.4Al 1.6Si 2.4O 8) dissolution rates were measured using a mixed flow reactor from 30 to 130°C as a function of dissolved CO 2 (1.2×10 −5 and 0.6 M), and aluminum (10 −6 to 10 −3 M) at pH 3.2. Over these experimental conditions, labradorite dissolution can be described with a single rate expression that accounts for observed increases in dissolution rate with increasing temperature and decreases in dissolution rate with increasing dissolved aluminum: (A1) Si Rate ( mol Labradorite cm − 2 s − 1 ) = k × 10 − E a / 2.303 ⁢ R ⁢ T [ ( a H + 3 ⁢ n / a Al 3 + n ) K T / ( 1 + K T ( a H + 3 ⁢ n / a Al 3 + n ) ) ] Si Rate where the apparent dissolution rate constant, k=10 −5.69 (mol Labradorite cm −2 s −1) and the net activation energy, E a=10.06 (kcal mol −1). This temperature-dependent rate expression is partly based on the model proposed by Oelkers et al. (1994) [Oelkers, E.H., Schott, J., Devidal, J., 1994. The effect of aluminum, pH, and chemical affinity on the rates of aluminosilicate dissolution reactions. Geochim. Cosmochim. Acta, 58, 2011–2024.] in which the dependence of silicate dissolution rates on dissolved aluminum in acidic solutions is attributed to H +–Al 3+ exchange at the mineral surface and formation of silica-rich surface complexes. For this exchange reaction, regression of the experimental data yield a stoichiometric coefficient n=0.31 and an enthalpy of reaction Δ H=0.54 (kcal mol −1). The temperature dependence of the silica-rich surface complex formation constant, K T, was estimated from the van't Hoff equation and yielded K T=4.49 to 5.61 from 30 to 130 °C. Elevated CO 2(aq) concentrations enhance mineral dissolution indirectly by acidifying solution pH. At temperatures below 100 °C, labradorite dissolves incongruently with preferential dissolution of Na, Ca, and Al over Si.

INHIBITION EFFECT OF DODECYL BENZENE SULFONATE (DBS) ON CORROSION OF IRON AND ALUMINUM IN ACIDIC SOLUTIONS BY WEIGHT LOSS METHOD

Article INHIBITION EFFECT OF DODECYL BENZENE SULFONATE (DBS) ON CORROSION OF IRON AND ALUMINUM IN ACIDIC SOLUTIONS BY WEIGHT LOSS METHOD was published on June 1, 2004 in the journal Corrosion Reviews (volume 22, issue 3).

Photoluminescence and optical absorption caused by the F+ centresin anodic alumina membranes

Anodic alumina membranes (AAMs) with highly ordered nanochannel arrays wereprepared by anodizing aluminum in acid solutions. X-ray diffraction revealsthe amorphous nature of AAMs. The photoluminescence (PL) excitation spectraof AAMs consist of a broad band centred at 235 nm and a narrow band peakingaround 360 nm under a monitoring wavelength of 470 nm. There are fiveprominent absorption bands (or edges) at 370, 294, 254, 220 and204 nm in the absorption spectra of AAMs prepared in oxalic solution. Withthe increase of the annealing temperature, the intensities of PL andabsorption bands increase first, then decrease, and a blue-shift is found.The photoluminescence and optical absorption in the wavelength range of200 nm to 500 nm are caused by the F+ centres in AAMs. The energy levelsof F+ centres in AAMs are split and a new energy level of 3.35 eVappears due to the amorphous nature of AAMs.

The mechanism of stress generation during the growth of anodic oxide films on pure aluminium in acidic solutions

The mechanism of stress generation during the anodic oxidation of pure aluminium in aqueous H2SO4 solutions has been explored using a.c. impedance spectroscopy and a beam deflection technique. From the analysis of a.c. impedance data, the resistance of the anodic oxide film was found to decrease as it grew progressively in 0.5 M H2SO4 solution, indicating an increase in the concentration of aluminium vacancies VAl3−(ox) within the film. From measurements of the deflection, compressive stresses were always observed at relatively low current density of 2 mA cm−2 during the growth of the film in aqueous H2SO4 solutions. Based upon the experimental results obtained from this work, it is suggested that stresses developed which determine the sign and magnitude of the deflections, are not distributed entirely over the whole oxide film, but are limited to a narrow region of the aluminium/oxide film interface below 1 nm. The changes in the sign and magnitude of stresses were satisfactorily accounted for in terms of the annihilation of VAl3−(ox) and the generation of oxygen vacancies VO2+(ox) at the aluminium/oxide film interface. From this, a new model for stress generation during the anodic oxidation of valve metals has been developed.

Growth mechanism of anodic oxide films on pure aluminium in aqueous acidic and alkaline solutions

The present work was conducted to explore the growth mechanism of anodic oxide films on pure aluminium in aqueous acidic and alkaline solutions by using a.c. impedance spectroscopy and a beam deflection technique. From the analyses of a.c impedance data, it was found that the reciprocal capacitance of anodic oxide film on pure aluminium increased linearly with increasing film formation potential in both acidic and alkaline solutions, indicating a linear increase in the film thickness with film formation potential. However, as the film formation potential increased, the resistance of anodic oxide film decreased in acidic solution, while it increased in alkaline solution. From the measurements of the deflection, the deflection was observed to move towards only a compressive direction with time in acidic solution, but it showed a transition in the direction of movement from compressive to tensile in alkaline solution. Based upon the above experimental results, it is suggested that the movement of oxygen vacancy through the oxide film contributes to the growth of anodic oxide film on pure aluminium in acidic solution, but the movement of both aluminium vacancy and oxygen vacancy accounts for that oxide film growth in alkaline solution.

Surface Films Produced by Cathodic Polarization of Aluminum

Cathodic polarization of aluminum in acid solution produces a surface film which was studied using infrared reflectance spectroscopy (IRS), and quartz crystal microbalance (QCM), and capacitance measurements. According to the QCM results, deposition of the film began after passage of 7.2 mC/cm2 of cathodic charge at a potential of −2.0 V. This charge was consistent with IRS and capacitance measurements. The film grew at an approximately constant rate with time, indicating that its ionic conduction resistance is small. Also, the linear increase of the reciprocal capacitance as a function of film mass is consistent with film growth occurring uniformly across the electrode surface. IRS showed that the cathodic film is an amorphous aluminum hydroxide or oxyhydroxide which contains absorbed water; QCM stripping measurements found that there was at least one water molecule per aluminum ion. This extensive hydration is perhaps related to the relatively low ion transport resistance. Mass transport calculations indicated that the film was formed by direct electrochemical growth and not by precipitation.

モリブデンオキシ水酸化物皮膜を利用したアルミニウムアノード酸化皮膜の物性の向上

It was found that a two-step anodizing process to form porous oxide films on aluminum, consisting of cathodic deposition of Mo (V)-Mo (VI) mixed oxyhydroxide films on aluminum from an ammonium molybdate solution followed by anodizing of the aluminum in acid solutions, results in films having improved mechanical properties. Anodic oxide films formed in a sulfosuccinic acid solution by the present process showed an increase in Vickers hardness of about 20% and the best results were Hv50=690±23 (±1σ) for cross section. The process is being extended using chromate treatment in the first step, and further improvements in physicochemical properties are expected.

The Synthesis of C-Nucleoside Precursors. II. Synthesis and Conformational Analysis of 3-(Pentahydroxypentyl)-6-phenyl-1,2,4-triazolo[3,4-a]phthalazines

Abstract Reaction of 1-hydrazino-4-phenylphthalazine with aldohexoses (d-galactose, d-glucose, d-mannose, and d-talose) and 6-deoxyaldohexoses (l-fucose and l-rhamnose) gave the colored aldehydo-sugar (4-phenyl-1-phthalazinyl)hydrazones or the colorless 3-(pentahydroxypentyl)-6-phenyl-1,2,4-triazolo[3,4-a]phthalazines. The former can be cyclized to the latter by catalytic dehydrogenation. Structure elucidation of the prepared compounds was made on the basis of their various spectral properties. The C-nucleoside precursors were further characterized as their O-acetyl derivatives and the configurational–conformational correlation of these acetates was studied. Some of the prepared compounds were screened for insectidicidal, nematicidal, and herbicidal activities and found to be inactive. They showed, however, good corrosion inhibition of aluminium in acid solutions.

Effect of fluoride on the amount of aluminium dissolved by boiling fruit acids

Boiling citric and tartaric acids dissolved aluminium from sheets and pans made of this metal. Fluoride increased the amount of aluminium dissolved by both citric and tartaric acids at the sort of concentrations which might be used in normal cookery (0·2%, pH 2·6). Increasing the amount of fluoride increased the amount of dissolved aluminium. The proportional increase was greater at low fluoride levels. Acids varied in their individual effects; tartaric acid dissolved considerably more aluminium than citric acid under any given set of conditions. The longer an acid solution was boiled with aluminium, the more of the metal dissolved. Repeated boiling of aluminium in acid solutions did not necessarily alter its response to further boiling. Old pans were attacked more strongly by acid solutions when fluoride was present. The precise composition of the aluminium metal used did not affect any of these conclusions.

ChemInform Abstract: The Inhibitive Action of Some Furfural Derivatives Towards the Corrosion of Aluminium in Acid Solution

Abstracthas been demonstrated by galvanostatic polarization and mass loss methods.

酸性溶液中におけるＡｌのアノード酸化時の電圧‐電流特性の解釈

An attempt is made to explain steady voltage-log current (Ea-log ia) curves obtained for the anodization of aluminum in acid solutions, by applying a theory so far reported for high-field ion conduction in crystalline solids. The theory is modified to some extent by taking into account two factors: the semi-spherical shell structure of the barrier layer by which the applied voltage is sustained, and the formation and repair of defects in the barrier layer which are appreciable at higher voltages. The interpreation of Ea-log ia behavior, including the effect of temperature, is quite satisfactory.

Influence of ethylenediamine on the surface charge of boehmitized aluminium

In a continuation of our investigation of boehmitized aluminium in aqueous solutions the interface was studied in the presence of ethylenediamine which is known to be a corrosion inhibitor for aluminium in acidic solutions. The methods of contact angle and electro-osmosis were used; both methods gave significant results and the influence of ethylenediamine was experimentally established. A parallelism is evident in the positions of the maximum contact angle and of the isoelectric point as functions of the solution pH. In the discussion the presence and equilibrium concentrations of the possible species originating from the ethylenediamine (one un-ionized and two ionized forms) are first accounted for by considering both dissociation constants for ethylenediamine. The influence of the substrate is considered by application of the Hammett concept for the acidic strength of the surface.

アルミニウム交流電解時における微分リサジュー図の測定法

Deformation of alternating current waves has been observed when so called ‘a. c. oxide films’ are formed on aluminum in acid solutions. Similar deformation was also recognized in an electrolytic coloring process in which anodized aluminum specimens were treated with altenating current in a solution containing metal ions. In this investigation, the authors have developed a new method to analyze the deformed current waves by measuring ‘Differential Lissajous’ Figures' with a special differentiation circuit. The method has an important advantage of indicating the Faradaic part of a. c. on a synchroscope. Results of experiments obtained for a. c. anodizing and a. c. coloring processes are described.

Mechanism of open-circuit dissolution of porous oxide films on aluminium in acid solutions

Electron micrographs of the vertical sections of porous anodic oxide films on aluminium immersed in acid solution were taken at time intervals after cutting the anodizing current. The result shows that the open-circuit dissolution of films proceeds in such a manner that pore widens at a constant rate at any depth of the pore. This is considered to be a conclusive evidence to support the “simple pore-widening mechanism” we have proposed in preceding papers.

Electrolytic hydrogen evolution reaction on aluminum in acidic solutions

Electrolytic hydrogen evolution reaction on aluminum in acidic solutions