Ion-containing Solutions Research Articles

Swelling and Metal-Ion Adsorption Properties of Dopamine-Conjugated Polyaspartate Hydrogel

Biodegradable hydrogels based on dopamine-modified polyaspartate were prepared, and the swelling behavior was investigated along with their metal-ion adsorption property. The catechol group of dopamine is well known to exhibit unique adhesive characteristics on a variety of organic/inorganic surfaces. Dopamine-modified polysuccinimide (DOP-PSI) was prepared by nucleophilic reaction of dopamine to polysuccinimide, and then crosslinked by adding diaminobutane as the crosslinker to yield an organogel in DMSO. Subsequently, the DOP-PSI gel was hydrolyzed in a pH9 buffer solution to produce the final, water-swollen hydrogel of DOP-modified polyaspartate (DOP-PASP). The swelling property of DOP-PASP was investigated in various aqueous solutions containing different metal-ions. The swelling degrees of the resulting gels were variable depending on the preparation conditions, such as polymer concentration and crosslinker level, though greater swelling of 450 g/g was observed in water. In ion-containing solutions, the swelling decreased as the ion concentration increased. As the valency of the ion increased, (i.e., Na+1 < Ca+2 < Fe+3) the swelling decreased abruptly due to the different ion-binding abilities of carboxylate and catechol groups with metal-ions. Adsorption of Fe+3 ions in aqueous solution was examined to show a high adsorption capacity of 270 mg/g-gel approximately. The results suggest that DOP-PASP has the potential for use as a hydrogel adhesive and metal-ion absorbing material.

Incorporation of selenium ions in solution-processed Cu(In,Ga)Se2 films

Cu(In,Ga)Se2 films were prepared on the molybdenum-coated soda-lime substrate using various processes to incorporate selenium ions. Selenium ion-containing solutions and selenium vapor were both used as the sources of selenium. When the precursors of Cu(In,Ga)Se2 were coated with selenium ion-containing solutions, the formation of MoSe2 was detected via secondary ion mass spectroscopy and GIXD analysis. The formation of thick MoSe2 films tended to retard the formation of Cu(In,Ga)Se2 and reduced the grain size of the prepared films. Therefore, the thick MoSe2 layer led to a decrease in the fill factor and the short-circuit density of the fabricated Cu(In,Ga)Se2 solar cells. The selenium ion-containing solutions were found to be easily evaporated during the heating process, thereby resulting in a decrease in the thickness and the porous microstructures of films. The decrease in the thickness of Cu(In,Ga)Se2 led to the decrease in the fill factors and the short-circuit density of the fabricated devices. The efficiency of Cu(In,Ga)Se2 solar cells prepared via selenium vapor was higher than that prepared via selenium ions. The photovoltaic characteristics of the fabricated solar cells were demonstrated to depend substantially on the routes of supplying and incorporation of selenium ions at elevated temperatures.

Selective accumulation of rare earth metal and heavy metal ions by a DNA-inorganic hybrid material

A DNA-inorganic hybrid film (DNA film) was prepared by mixing DNA and a silane coupling reagent, bis(trimethoxysilylpropyl)amine. This DNA film can accumulate heavy metal ions in aqueous solution. We have demonstrated the accumulation of rare earth metal and heavy metal ions using DNA-inorganic hybrid-immobilized glass beads (DNA beads), which were prepared by coating the DNA-inorganic hybrid onto glass beads. When these DNA beads were placed in an aqueous solution of metal ions and incubated for 24 h (batch method), the DNA beads selectively accumulated heavy metal and rare earth metal ions. The maximum-accumulated amounts of Cu2+, Cd2+, In3+ and La3+ were ∼1.2, 0.94, 1.6 and 1.3 μmol, respectively, for 1 mg of DNA (3.0 μmol of nucleotide). The molar ratio of DNA to a metal ion was nucleotide:metal ion=1:0.5. Finally, we demonstrated the accumulation of metal ions by a DNA-bead column (DNA column). As a result, the DNA column effectively accumulated the heavy metal and rare earth metal ions. The DNA column was recycled by washing with an EDTA solution. DNA-immobilized glass beads (DNA beads) were prepared by coating DNA-inorganic hybrid material onto glass beads. When these DNA beads were placed in an aqueous metal ion-containing solution and incubated (batch method), the DNA beads selectively accumulated the heavy and rare-metal ions, such as Cu2+, Cd2+, In3+ or La3+. Therefore, we demonstrated the accumulation of metal ions by a DNA-immobilized glass bead column (DNA column). As a result, the DNA column effectively accumulated the heavy and rare-metal ions. Furthermore, the DNA column could be recycled by washing it with an aqueous EDTA solution.

Determination of carbohydrate‐deficient transferrin in human serum by capillary zone electrophoresis: Evaluation of assay performance and quality assurance over a 10‐year period in the routine arena

The performance of high-resolution CZE for determination of carbohydrate-deficient transferrin (CDT) in human serum based on internal and external quality data gathered over a 10-year period is reported. The assay comprises mixing of serum with a Fe(III) ion-containing solution prior to analysis of the iron saturated mixture in a dynamically double-coated capillary using a commercial buffer at alkaline pH. CDT values obtained with a human serum of a healthy individual and commercial quality control sera are shown to vary less than 10%. Values of a control from a specific lot were found to slowly decrease as function of time (less than 10% per year). Furthermore, due to unknown reasons, gradual changes in the monitored pattern around pentasialo-transferrin were detected, which limit the use of commercial control sera of the same lot to less than 2 years. Analysis of external quality control sera revealed correct classification of the samples over the entire 10-year period. Data obtained compare well with those of HPLC and CZE assays of other laboratories. The data gathered over a 10-year period demonstrate the robustness of the high-resolution CZE assay. This is the first account of a CZE-based CDT assay with complete internal and external quality assessment over an extended time period.

363 KのCl&lt;sup&gt;－&lt;/sup&gt;およびCu&lt;sup&gt;2＋&lt;/sup&gt;イオンを含む水溶液中におけるAlおよびAl合金の腐食

Cu2＋あるいはCl－イオンを含む高温水溶液中（363 K）にAlおよびAl合金を浸漬したさい，それらの腐食挙動がインヒビターの添加によりどのように変化するかを，質量測定および試料の表面・縦断面観察により調べた．インヒビターの添加により，Cu2＋溶液において腐食速度は大きく抑制されるのに対し，Cl－溶液中においては，ほとんど変化しなかった．Cu2＋溶液におけるインヒビターの防食効果は，SiO2薄膜形成によるCu粒子の析出の抑制によることがわかった．

Transferrin immunoextraction for determination of carbohydrate-deficient transferrin in human serum by capillary zone electrophoresis

CZE-based assays for carbohydrate-deficient transferrin (CDT) in which serum is mixed with an Fe(III) ion-containing solution prior to analysis are effective approaches for the determination of CDT in patient samples. Sera of patients with progressed diseases, however, are prone to interferences comigrating with transferrin (Tf) that prevent the proper determination of CDT by CZE in these samples. The need of a simple and economic approach to immunoextract Tf from human serum prompted us to investigate the use of a laboratory-made anti-Tf spin column containing polyclonal rabbit anti-human Tf antibodies linked to Sepharose 4 Fast Flow beads. This article reports extraction column manufacturing and column characterization with sera having normal and elevated CDT levels. The developed procedure was applied to a number of relevant hepatology and dialysis patient samples and could thereby be shown to represent an effective method for extraction and concentration of all Tf isoforms. Furthermore, lipemic sera were delipidated using a mixture of diisopropyl ether and butanol prior to immunoextraction. CDT could unambiguously be determined in all pretreated samples.

Photochromic behavior of spironaphthoxazine in metal ion-containing solutions

The isomerization and metal chelation of spironaphthoxazine (SNO) in ethanol solutions have been investigated by measuring the UV–vis absorption spectra as a function of time. The protonated species of merocyanine (MC), an isomer of SNO, was gradually formed in the solutions containing SNO and aluminum ions in the dark. The proton was provided by the reaction of the aluminum ions with a slight amount of water contained in the ethanol solvent. The protonated species was slowly transformed into the aluminum chelate complex of MC by ligand exchange of the ethanol-solvated aluminum for MC in the dark. UV irradiation promoted the isomerization and chelation without forming the protonated species. The spectroscopic analysis with various compositional ratios of SNO and aluminum ions revealed that one aluminum ion was coordinated to three bidentate MC ligands in the ethanol solution.

Selective Growth and SERS Property of Gold Nanoparticles on Amorphized Silicon Surface

We have fabricated gold patterns on a silicon substrate by a simple three-step method using a focused ion beam (FIB). The obtained gold patterns consisted of a large number of gold nanoparticles which grew selectively on the preprocessed silicon surface from an Au ion-containing solution dropped on the substrate. The solution was prepared by reacting HAuCl4 aqueous solution with (3-mercaptopropyl)trimethoxysilane (MPTMS). It was found that the size and shape of the precipitating gold nanoparticles is controllable by changing the mixing ratio between HAuCl4 aqueous solution and MPTMS. Additionally, we confirmed that the fabricated gold structures were surface enhanced Raman scattering (SERS)-active; the enhanced Raman peaks of rhodamin 6G (R6G) were detected on the fabricated gold structures, whereas no peak was detected on the alternative silicon surface. We also demonstrated the gold patterning using a femtosecond laser instead of an FIB. We believe that our method is a favorable candidate for fabricating SERS-active substrates, since the substrates can be prepared very simply and flexibly.

Structure evolution of pure titanium under different polishing conditions

Pure titanium is a soft material. Its surface structure changes under different polishing conditions. In this work, mechanical polishing, chemical-mechanical polishing and electrochemical polishing pure titanium were performed to study the surface structure evolution. For mechanical polishing, it is hard to obtain scratch free surface using alumina fine particles as the abrasives. Chemical-mechanical polishing using 10% hydrogen peroxide can generate much more smooth surface. For the case of electrochemical polishing using fluorine ion-containing solutions after either mechanical or chemical-mechanical polishing, different surface features were observed depending on the electrochemical polishing parameters used. When the voltage was controlled lower than 10 V, the grain structure of Ti and etching pits were revealed. The material removal rate was calculated based on the data obtained from cyclic voltammetry tests. If the voltage was kept at 20 V, surface nanostructures including nanopores and nanotubes were found. The self-organised titanium oxide nanotubes were aligned vertically to the polished surface. Scanning electron microscopic analysis was carried out to reveal the surface structure evolution. In addition, elemental analysis using energy dispersive X-ray diffraction technique was conducted to show the composition of the surface nanostructures.

Effectively Inhibiting Abnormal Grain Growth of Alumina in ZTA with Low‐Content Fine‐Sized ZrO2 Inclusions Introduced by Infiltration and In Situ Precipitation

Previous literatures have all emphasized that the successful control of microstructure homogeneity of ZTA (ZrO2 toughened Al2O3) composites can only be achieved provided that the ZrO2 particles are homogeneously distributed and the volume content exceeds 5 vol%. In this paper, we report our strategy to incorporate fine‐sized ZrO2 into Al2O3 by infiltrating presintered alumina compact using zirconium ion‐containing solution and then in situ precipitation with ammonia solution. Homogeneous microstructure without AGG can be achieved in the prepared composite at a lower ZrO2 content (2.3 vol%). Such a result might be attributed to the excellent homogeneous distribution of fine‐sized incorporated ZrO2 particles in Al2O3 matrix.

Preparation and Characterization of Polypyrrole Silver Nanocomposites via Interfacial Polymerization

Conducting polypyrrole silver (Ppy-AgNC) nanocomposite was synthesized by an interfacial polymerization method. Ag+ ions from the AgNO3 solution were taken in the formation of Ppy-AgNC. The incorporated silver was confirmed by X-ray diffraction (XRD). During the polymerization in a nitrate ion-containing solution, the impregnation leads to the formation of metallic silver. The size distribution of Ag into the polymer is confirmed by transmission electron microscopy (TEM), and proves the formation of a uniform species with spherical particles of Ag (mean diameter of 8-12 nm) branching at the border of Ppy. The thermal behavior of the material was studied by thermogravimetric measurements.

Effect of interface chloride ion perturbation on oscillatory electrodissolution

This paper investigated the effect of chloride ion perturbation on the electrodissolution behavior of carbon steel in 5.0 M H 3PO 4 solution. The results indicated that the oscillatory electrodissolution changes significantly when the electrode/electrolyte interface was disturbed by injecting small quality of chloride ion-containing solution. The mode of current oscillations changed from the mono-periodic to the nonperiodic behavior with higher frequencies but lower amplitudes. After a transient response disappeared, the permanent influence in the current oscillations was observed. Potential distributions on the surface of the electrode were monitored in situ by using scanning reference electrode technology during the electrodissolution process. The potential maps show clearly that localized corrosion was induced after the chloride perturbation. The enforced solution homogenization by bubbling nitrogen at the electrode/electrolyte interface after a few seconds of the chloride perturbation could not eliminate such influence, indicating that chloride ions may enter the passive film and resulted in degradation in chemical stability of the film because of permanent damage. Such a degradation of the passive film only appears when the transient concentration gradient of the chloride ions on the surface is sufficiently high. The long duration of impact on electrodissolution caused by chloride ion perturbation suggests that the passive film does not totally dissolve during the active period in each oscillatory cycle.

Novel One-Step Aqueous Solutions to Replace Pregate Oxide Cleans

We have developed a number of novel solutions to use for one-step pregate oxide cleaning; they are based on tetraalkylammonium hydroxides of varying alkyl chain lengths, namely tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide (TPAH), and tetrabutylammonium hydroxide (TBAH). We added these surfactants together with ethylenediaminetetraacetic acid (EDTA) into the RCA SC-1 cleaning solution to enhance the efficiency of cleaning. With the exception of the TBAH solution, the cleaning efficiency of these solutions toward particles was 4%-7% higher than that of the conventional RCA method. Our cleaning methods have better efficiency toward the removal of Fe, Na, Ca, Cu, and Mn contaminants. We found that the conventional RCA method results in 10/sup 9/-10/sup 10/ atoms/cm/sup 2/ of Cu and Mn after cleaning. The electrical breakdown field of MOS capacitors was enhanced when using the new cleaning method. The literature model for surface adsorption and double-layer formation explains the cleaning behavior of the tetraalkylammonium ion-containing solutions. The removal of surface particles and metallic contaminants and the degree of surface roughness agree with the model's predictions. We believe that the best solution for use in one-step cleaning-one that comprises EDTA and TPAH-can replace the traditional RCA cleaning method. This new method has great potential for pregate oxide cleaning because it has the advantages of faster cycle times, lower costs, and greater efficiency.

Fractal analysis of pit morphology of Inconel alloy 600 in sulphate, nitrate and bicarbonate ion-containing sodium chloride solution at temperatures of 25?100��C

Pit morphology of Inconel alloy 600 in sulphate (SO4 2-), nitrate (NO3 -) and bicarbonate (HCO3 -) ion-containing 0.5 M sodium chloride (NaCl) solution was analysed in terms of fractal geometry as functions of solution temperature and anion concentration using the potentiostatic current transient technique, scanning electron microscopy, image analysis and ac-impedance spectroscopy. Potentiostatic current transients revealed that the pitting corrosion is facilitated by the increase in solution temperature, irrespective of anion additives, and that it is hindered by the increase in NO3 - and HCO3 - ion concentration, regardless of solution temperature. Above 60 °C, it was also found that the addition of SO4 2- ions impedes pit initiation, but enhances pit growth. The value of fractal dimension D f of the pits increased with increasing solution temperature and with decreasing NO3 - and HCO3 - ion concentration. Moreover, the value of D f increased above 60 °C with increasing SO4 2- ion concentration. This is caused by the increase in the ratio of pit perimeter to pit area, implying the formation of pits with micro-branched shape due to the acceleration of the local attack in the pits. From the decrease of the depression parameter with increasing solution temperature, it is inferred that the roughness of the pits increased with increasing solution temperature. In addition, the depression parameter was found to increase with increasing NO3 - and HCO3 - ion concentration. But, above 60 °C, in the case of SO4 2- ion addition, the depression parameter decreased with increasing SO4 2- ion concentration. From the experimental findings, the three-dimensional pit morphology is discussed in terms of the values of D f of the pits and the depression parameter, with respect to anion concentration and solution temperature.

Behaviour of Cadmium(II) Ions on Cation-Exchange Resins

Cadmium is one of the most toxic heavy metals known and is considered inessential for living organisms. This element is found at low concentrations in natural environments, but human activities have led to increased levels in all continents. In the present study, the removal of cadmium(II) ions from aqueous solutions was investigated. Experimental investigations were undertaken using the ion-exchange resins Amberlite IR 120 (strongly acidic), Amberlite IRC 718 (weakly acidic and chelating), Lewatit TP 207 (weakly acidic and chelating) and Lewatit CNP 80 (weakly acidic). For investigations of the exchange equilibria, different amounts of resin material were contacted with a fixed volume of a cadmium ion-containing solution. Because the uptake of cadmium ions was mainly dominated by the pH of the liquid phase, the pH value was varied between 0 and 3 with sample sizes of 0.5-5.0 g in each series studied. The initial and final cadmium ion concentrations were measured by ICP-AES methods. Exchange equilibria we...

Analysis of impedance spectra of a pitted Inconel alloy 600 electrode in chloride ion-containing thiosulfate solution at temperatures of 298–573 K

In the present work, impedance spectra of a pitted Inconel alloy 600 electrode were analysed in aqueous 0.1 M Na2S2O3+0.1 M NaCl solution at elevated solution temperatures of 298–573 K and at pressures of 0.1–8 MPa in terms of pit size distribution, fractal dimension and surface roughness in sequence as the solution temperature rose. From impedance spectra of the Nyquist plot obtained from the pitted specimen exposed to solutions at temperatures of 60–150°C, a constant phase element (CPE) was observed in the frequency range from 103 to 1 Hz. Especially, it was found that the impedance spectra were divided into two sections, i.e. a first CPE with a smaller slope in the higher frequency range and a second CPE with a larger slope in the lower frequency range. The occurrence of the two kinds of CPE results from a transition of ion diffusion through the pit to ion accumulation at the pit bottom, which is caused by double-layer charging at the pit bottom and prior double-layer charging at the pit wall. Impedance spectra were simulated in terms of pit size distribution and values of the fractal dimension of the pits as a function of solution temperature to compare with those spectra measured experimentally. The spectra were simulated based upon the conventional transmission line model for a cylindrically shaped pit at 60 °C and on the basis of a modified transmission line model for the triadic Koch construction at 100 °C and for the quadratic Koch construction at 150 °C. The modified transmission line model takes into account the resistive and capacitive elements in the lateral direction as well as those in the downward direction of the three-dimensional Koch constructions. Above 200 °C the Nyquist plots were found to be depressed more noticeably from a perfect semicircular form with increasing solution temperature. This is due to the increase in the surface roughness of the specimen by the formation and growth of the pits.

Polymer electrolyte membrane for electrochemical applications

Mineralization of collagen fibrils using solution-based systems containing biomimetic analogs of matrix proteins to stabilize supersaturated calcium phosphate solutions have been predictably achieved in vitro. Solution-based systems have limitations when used for in-situ remineralization of human hypomineralized tissues because periodic replenishment of the mineralizing solution is infeasible. A carrier-based platform designed for delivering mineral precursors would be highly desirable. In the present work, mesoporous silica nanoparticles with expanded pores (eMSN; 14.8 nm) were synthesized. Polyacrylic acid–stabilized amorphous calcium phosphate (PA–ACP) was generated from a supersaturated calcium and phosphate ion-containing solution, and chosen as the model mineralizing phase. After amine functionalization (AF) of the eMSN through a post-grafting method, the positively-charged AF-eMSN enabled loading of PA–ACP by electrostatic interaction. In-vitro cytotoxicity testing indicated that PA–[email protected] was highly biocompatible. The release kinetics of mineralization precursors from PA–[email protected] was characterized by an initial period of rapid calcium and phosphate release that reached a plateau after 120 h. Intrafibrillar mineralization was examined using a 2-D fibrillar collagen model; successful mineralization was confirmed using transmission electron microscopy. To date, this is the first endeavor that employs expanded-pore mesoporous silica to deliver polymer-stabilized intermediate precursors of calcium phosphate for intrafibrillar mineralization of collagen. The carrier-based delivery system bridges the gap between contemporary solution-based biomineralization concepts and clinical practice, and is useful for in-situ remineralization of bone and teeth.Concepts of collagen biomineralization have been reasonably well established in the past few years and intrafibrillar mineralization of collagen fibrils can be predictably achieved with analogs of matrix proteins using solution-based systems. However, solution-based systems have their limitations in clinical applications that require direct application of mineralization precursors in-situ because periodic replenishment of the mineralizing solution is impossible. The present work presents for the first time, the use of amine-functionalized mesoporous silica with expanded pores for loading and release of polyacid-stabilized amorphous calcium phosphate mineralization precursors, and for intrafibrillar mineralization of type I collagen fibrils. This strategy represents an important step in the translational application of contemporary biomineralization concepts for in-situ remineralization of bone and teeth.

Selectivity of metal cations and lithium isotopes on ion exchangers in the hydrogen form prepared by thermal treatment of NH4Zr2(PO4)3

NH4Zr2(PO4)3 with different particle sizes and different specific surface areas were obtained by controlling the preparation conditions. HZr2(PO4)3, cation exchangers in the hydrogen form, were prepared by the thermal treatment of NH4Zr2(PO4)3 in the temperature range of 400 to 700°C and their ion exchange properties were investigated with the main focus on the selectivity for group I and II metal ions and lithium isotopes. Irrespective of the temperature of the thermal treatment, HZr2(PO4)3 showed especially high affinity toward the lithium ion, high affinity toward the sodium ion and had little selectivity for the rubidium and cerium ions from the group I metal ions, and showed no specific affinity toward any of group II metal ions. HZr2(PO4)3 were isotopically 6Li-specific in any conditions examined. The 6Li-to-7Li isotopic separation factor was nearly independent of temperature of the thermal treatment. It depended, however, on the pH of lithium ion-containing solution used as the solution phase in an ion exchange experiment. This pH dependence of the lithium isotope separation effect was due to the appearance of the LiZr2(PO4)3 phase and/or the hydration number of the lithium ion in the ion exchanger phase.

Structure Control of Ion Exchange in N-Octadecanoyl-l-alanine Langmuir−Blodgett Films Studied by FTIR Spectroscopy

Ion transport and ion exchange in two-dimensional N-octadecanoyl-l-alanine Langmuir−Blodgett (LB) films were studied through FTIR spectroscopy. At the intrinsic pH values of the ion-containing solutions (without any adjustment), the metal ions penetrating into the LB films are selectively exchanged with the carboxylic acid groups of film-forming molecules. This behavior is different from the interactions between the metal ions in aqueous subphases and the corresponding monolayers at the air−water interface. Ion exchange in the N-octadecanoyl-l-alanine LB films is controlled by the structure of the intermolecular hydrogen-bonding network. Ion exchange is favorable to Zn2+and Ag+ ions, as it promotes an increase of intermolecular hydrogen bonds and a decrease of intermolecular distance. Ion exchange is unfavorable to Ca2+, Cd2+, and Ni2+ ions, as it is suppressed by the occurrence of intramolecular hydrogen bonds and the increase of intermolecular distance. The reverse exchange process by protons is consistent with the above results. Ion exchange is unfavorable to zinc and silver salts, as it is suppressed by the weakening of intermolecular hydrogen bonds and the increase of intermolecular distance, and it is extremely favorable to calcium, cadmium, and nickel salts in converting from intramolecular to intermolecular hydrogen bonds.

Effects of sulphate ion additives on the pitting corrosion of pure aluminium in 0.01 M NaCl solution

Effects of sulphate (SO 4 2−) ion additives on the pitting corrosion of pure aluminium (Al) have been investigated in aqueous 0.01 M NaCl solution as a function of SO 4 2− ion concentration using potentiodynamic polarisation experiment, ac impedance spectroscopy, electrochemical quartz crystal microbalance technique and abrading electrode technique. The addition of SO 4 2− ions to NaCl solution raised the pitting potential ( E pit) of pure Al in value and simultaneously the anodic current density at potentials much higher than the E pit on the polarisation curves. This implies that SO 4 2− ions impede the initiation of pit on pure Al surface below the E pit, but enhance the growth of pre-existing pits, which is validated by optical microscopy. It was found that the values of the Cl − ion-incorporated outer film resistance R out,ox in SO 4 2− ion-containing chloride solutions were much lower than those in SO 4 2− ion-free solution, obtained from the impedance spectra measured at potentials below the E pit. The chloride peak disappeared from the Auger spectra in SO 4 2− ion-containing solutions. The mass decay rate and pit growth rate b were observed to increase in values once the pits were formed in SO 4 2− ion-containing chloride solutions. Based upon the above experimental results, it is suggested that SO 4 2− ions retard the oxide film breakdown by Cl − ion incorporation into the film, while they accelerate the Al metal dissolution through the instantaneous formation of tunnels at the bottom of the pre-existing pits after the exposure of bare surface above the E pit.