Influence Of Chloride Concentration Research Articles

Electropolishing of gold and gold alloys in HCl-glycerol-ethanol electrolytes

Electropolishing or electrochemical polishing (EP) is an ultrafinishing process that improves esthetic, technical and functional properties of metallic surfaces by reducing their roughness. This process is based on anodic dissolution of the workpiece through an oxidation reaction. For many years, cyanide-based electrolytes were used to electropolish precious metals like gold and its alloys. The need for safer working conditions encouraged the replacement of cyanide by other complexing agents, mainly thiourea. However, the latter is also harmful. Therefore, the aim of this work is to electropolish pure gold and 18k jewelry gold alloys (yellow, rose, red and gray) in a cyanide-free electrolyte, to evaluate the electrochemical behavior and the influence of different parameters. For this purpose, a previously reported solution based on hydrochloric acid and glycerol was used. In the first part of the study, the influence of chloride concentration on pure gold EP was determined by electrochemical techniques and surface properties analysis. The effects of adding ethanol to electrolyte composition and of variating rotation speed were also evaluated. The best results were obtained for a HCl 50% vol. - Glycerol 25 % vol. - Ethanol 25 % vol. electrolyte at a rotation speed of 1000 rpm. In the second part of the study, this solution was used to electropolish 18 K gold alloys. Silver-containing alloys were not uniformly polished due to the formation of an AgCl film on the surface that partially masks the substrates.

Analysis of chloride invasion process in undersea RC circular lined tunnel based on nonlinear ADE theory: Analytical solution, numerical verification and experimental prediction

In this paper, a new nonlinear chloride transport model is proposed for the problem of undersea RC circular lined tunnel corrosion. The model takes into account the advection effect induced by seawater pressure, the time-depending surface chloride concentration, the time-depending concrete parameters, the scale effect of initial chloride concentration and the seepage velocity varies with the radial direction of the tunnel. The analytical solution of the proposed model is derived by function transformation, eigenvalue system and integral transformation, of which accuracy is verified by comparison with FEM via hypothetical case. Subsequently, influence of chloride concentration in seawater, seawater pressure, diffusion coefficient of concrete, permeability coefficient of concrete, time-dependent surface chloride concentration model and time-dependent concrete parameter model on chloride penetration in the reinforced concrete of tunnel is especially discussed. Finally, the practical use of the proposed model is demonstrated by two groups of tests based on circular lined tunnel. The paper provides an effective and concise analytical solution to evaluate the chloride invasion of cylindrical tunnel.

Current distribution and throwing power of galvanic cathodic protection with discrete anodes in reinforced concrete beam or column elements

Galvanic cathodic protection (GCP) of steel in concrete by means embedded discrete anodes is a commonly used repair method to reduce or prevent steel reinforcement corrosion. The design and efficiency of the system depends greatly on the corrosion activity of the steel reinforcement and electrical resistivity of the concrete. In this research, the influence of chloride concentration and cement type in the concrete on the current distribution and throwing power of GCP with discrete anodes is investigated for linear concrete elements such as beams or columns. Results show a high throwing power (> 500 mm) of the GCP system for concrete with a CEM I cement (low resistivity) and limited chloride contamination. For concrete with a severe contamination of chlorides (2 m% by mass of cement) or high electrical resistivity (e.g. by the use of CEM III/A cement), the throwing power is greatly reduced to values of 60 mm and 110 mm, respectively. Consequently, based on the 100 mV depolarization criterium (EN ISO 12696:2016), GCP with discrete anodes was found to be most efficient for concrete with relatively low resistivity and limited corrosion activity of the steel reinforcement (related to chloride concentration in the concrete).

Influence of Chloride Concentration on Stress Corrosion Cracking and Crevice Corrosion of Austenitic Stainless Steel in Saline Environments.

Stainless steels are used as canister materials for interim storage of spent fuel. Crevice corrosion has proved to be a safety concern of 304L stainless steel spent fuel canisters, when exposed to the saline environments of coastal sites. To study the effects of chloride concentration and test duration on the crevice corrosion behavior, and the effect of relative humidity on the initiation of discrete SCC cracks, a test program was conducted on the 304L steel specimens sprayed with synthetic sea water of 3.5 wt.%. The salt-deposited specimens, wrapped up with a crevice former to form a crevice configuration, were then exposed to an environment at 45 °C with a pre-set 45%, 55%, and 70% relative humidity (RH), for 400 h and 10,000 h, respectively. The surface features and crack morphology of the tested 304L stainless-steel specimens were examined by energy-dispersive spectrometry (EDS) and electron back scatter diffraction (EBSD). For the specimens deposited with a chloride concentration of 1 g/m2, no cracks were found in the corroded regions after 400-h exposure, whereas SCC cracks were observed with the specimens tested for 10,000 h at all three pre-set relative humidity. The specimens tested at the pre-set relative humidity 45% are characterized with discrete SCC cracks, but, on the other hand, those exposed to the environments of 55% and 70% relative humidity show SCC cracks of distinct features. From the results of 10,000-h tests, it is inferred that the chloride concentration threshold for SCC initiation of 304L stainless steel at 45 °C is between 0.1 g/m2 and 1 g/m2.

Influence of Chloride Concentration on the Pitting Probability of Copper Using Coupled Multielectrode Arrays

The preferred disposal method for used nuclear fuel is to seal it in containers emplaced in a deep geologic repository (DGR) in a suitable rock formation. In Canada, the container is a robust steel vessel coated with 3 mm of Cu as a corrosion barrier. Eventually, the DGR environment will become anoxic, and in the absence of oxygen copper is thermodynamically stable in water. However, since exposure conditions will initially be oxidizing due to the presence of O2 trapped on sealing the DGR, there is a possibility of localized corrosion. Mass balance calculations show that uniform corrosion during this period will be within the designed corrosion allowance, however, since the Cu coating is relatively thin and the required lifetime is long, the risk of pitting corrosion during this period must be carefully evaluated.Pitting corrosion susceptibility is determined by the corrosion potential of the material (Ecorr, the potential at which the rates of all anodic and cathodic reactions are equal), and the breakdown potential (Eb, the potential at which the copper oxidation rate on the surface increases abruptly due to the breakdown of the protective film), both of which are distributed parameters, due to the stochastic nature of passive film rupture and any uncontrollable variations in the structure and local environment at the metal surface. It is important to note that the analysis is based on the concept that pitting is only possible if the Ecorr is equal to, or more positive than the Eb. In this work, a multielectrode array was used to obtain a statistically meaningful set of potential measurements through the simultaneous monitoring of 30 electrodes to determine their corrosion and breakdown potentials. From the extensive database thus acquired, we defined the Ecorr and Eb distributions for copper electrodes exposed to solutions containing various chloride concentrations. Our previous studies showed passive behavior of copper surface exposed to high pH solutions. Therefore, a more thorough evaluation of the relative values of Ecorr and Eb is required to determine the susceptibility to pitting. Experiments were conducted by using multielectrode array at 25 C and pH 11. In alkaline solutions, copper oxide is more stable and can form a passive film, whereas chloride promotes the breakdown of the passive film. As the chloride concentration increased, values of Ecorr and Eb decreased, suggesting that the solubility of copper increases with increasing chloride concentration. Therefore, the stability of the passive film is decreased in the presence of chloride.In general, the possibility of pitting increases with growing overlap between the distribution curves of Ecorr and Eb. To evaluate the possibility of pitting, histograms and distribution curves of Ecorr and Eb in the solutions what have different chloride concentrations were compared. In lower chloride concentrations, there was a very small overlap between Ecorr and Eb; consequently, the possibility of pitting under these conditions is very low. On the other hand, a high chloride concentration at high pH contributed to a higher probability of pitting, as the overlap between Ecorr and Eb distributions increased.

The anoxic corrosion behaviour of copper in the presence of chloride and sulphide

AbstractThe Canadian used fuel container for the long‐term containment of spent nuclear fuel in a deep geological repository comprises a 3‐mm copper corrosion barrier applied directly to a strong carbon steel container. Although a final site for the Canadian deep geological repository has not yet been chosen, the site selection process has narrowed down to two candidate locations with unique groundwater chemistry, particularly with respect to salinity. Therefore, to ensure the long‐term integrity of the used fuel container, the effect of a range of groundwater chemistries on copper corrosion must be understood. The primary variables of interest are the influence of chloride concentration and the consequences of the interaction of hydrogen sulphide, naturally present in the groundwaters in very low concentrations, with the copper cladding. An additional aspect that has been investigated is the behaviour of copper in pure water. The anoxic corrosion of copper can be inferred by the very slow release of hydrogen gas. In this paper, new data are presented, which demonstrate an extremely sensitive approach to quantify the very limited hydrogen release at 75°C. Initially, corrosion rates under conditions approximating an anticipated Canadian deep geological repository were significantly less than 0.5 nm/year and they invariably declined over the course of several months/years. The presence of chloride or hydrogen sulphide was found, under specific conditions, to stimulate short‐term corrosion behaviour, which was consistent with anion‐assisted surface rearrangement, not bulk corrosion.

Influence of Chloride Concentration on the Pitting Probability of Copper Using Coupled Multielectrode Arrays

The preferred disposal method for used nuclear fuel is to seal it in containers emplaced in a deep geologic repository (DGR) in a suitable rock formation. In Canada, the container is a robust steel vessel coated with 3 mm of Cu as a corrosion barrier. Eventually, the DGR environment will become anoxic, and in the absence of oxygen copper is thermodynamically stable in water. However, since exposure conditions will initially be oxidizing due to the presence of O2 trapped on sealing the DGR, there is a possibility of localized corrosion. Mass balance calculations show that uniform corrosion during this period will be within the designed corrosion allowance, however, since the Cu coating is relatively thin and the required lifetime is long, the risk of pitting corrosion during this period must be carefully evaluated.Pitting corrosion susceptibility is determined by the corrosion potential of the material (Ecorr, the potential at which the rates of all anodic and cathodic reactions are equal), and the breakdown potential (Eb, the potential at which the copper oxidation rate on the surface increases abruptly due to the breakdown of the protective film), both of which are distributed parameters, due to the stochastic nature of passive film rupture and any uncontrollable variations in the structure and local environment at the metal surface. It is important to note that the analysis is based on the concept that pitting is only possible if the Ecorr is equal to, or more positive than the Eb. In this work, a multielectrode array was used to obtain a statistically meaningful set of potential measurements through the simultaneous monitoring of 30 electrodes to determine their corrosion and breakdown potentials. From the extensive database thus acquired, we defined the Ecorr and Eb distributions for copper electrodes exposed to solutions containing various chloride concentrations. Our previous studies showed passive behavior of copper surface exposed to high pH solutions. Therefore, a more thorough evaluation of the relative values of Ecorr and Eb is required to determine the susceptibility to pitting. Experiments were conducted by using multielectrode array at 25 C and pH 11. In alkaline solutions, copper oxide is more stable and can form a passive film, whereas chloride promotes the breakdown of the passive film. As the chloride concentration increased, values of Ecorr and Eb decreased, suggesting that the solubility of copper increases with increasing chloride concentration. Therefore, the stability of the passive film is decreased in the presence of chloride.In general, the possibility of pitting increases with growing overlap between the distribution curves of Ecorr and Eb. To evaluate the possibility of pitting, histograms and distribution curves of Ecorr and Eb in the solutions what have different chloride concentrations were compared. In lower chloride concentrations, there was a very small overlap between Ecorr and Eb; consequently, the possibility of pitting under these conditions is very low. On the other hand, a high chloride concentration at high pH contributed to a higher probability of pitting, as the overlap between Ecorr and Eb distributions increased.

Effects of Chloride Concentration on the Water Disinfection Performance of Silver Containing Nanocellulose-based Composites

The availability of microbially-safe drinking water is a challenge in many developing regions. Due to the well-known antibacterial effect of silver ions, materials used for their controlled release have been widely studied for point-of-use water disinfection. However, even if it is in principle known that chloride anions can suppress the antibacterial efficiency of silver, the majority of previous studies, surprisingly, have not focused on chloride concentrations relevant for freshwaters and thus for practical applications. Here, we prepared low-cost nanocellulose-aluminium oxyhydroxide nanocomposites functionalized with silver nanoparticles. Field samples obtained from Chennai, India were used as a guideline for choosing relevant chloride concentrations for the antibacterial studies, i.e., 10, 90, and 290 ppm. The antibacterial performance of the material against Escherichia coli and Bacillus subtilis was demonstrated and the influence of chloride concentration on the antibacterial effect was studied with E. coli. A 1 h contact time led to bacterial reductions of 5.6 log10, 2.9 log10, and 2.2 log10, respectively. This indicates that an increase of chloride concentration leads to a substantial reduction of antibacterial efficiency, even within chloride concentrations found in freshwaters. This work enables further insights for designing freshwater purification systems that utilize silver-releasing materials.

On the Characteristic Potentials of Pitting Corrosion of Compact and Powder Steel

The influence of chloride concentration and current density on the characteristic potentials of pitting corrosion found during potentiodynamic E po pd and galvanostatic E po cr polarization and Erp repassivation of the PC process of 10Х17Н13М2Т and 12Х18Н10Т cast steels and 316L and 316L + 3% Сu 304HLD powder steels with addition of 10 and 15% Cu in a neutral chloride solution was studied. The porosity of the powder steel significantly decreases the pitting resistance. Addition of 3% Сu increases the pitting resistance, but does not allow achieving the pitting resistance level of compact molybdenum steel; neither does addition of 10 and 15% copper do so for 12Х18Н10Т steel.

Mapping the Corrosion Behavior of AZ91D Magnesium Alloy: Influence of Chloride Concentration and Potentiostatic Polarization

Mapping the Corrosion Behavior of AZ91D Magnesium Alloy: Influence of Chloride Concentration and Potentiostatic Polarization

Influence of chloride concentration and pre-passivation on the pitting corrosion resistance of low-alloy reinforcing steel in simulated concrete pore solution

The effect of chloride concentration and pre-passivation on the pitting corrosion resistance of low-alloy steel and conventional low-carbon steel in simulated concrete pore solution was investigated using electrochemical techniques and surface analysis measurements. The results show that the passive film could enhance the pitting corrosion resistance for both investigated steels. Low-alloy steel exhibits slightly lower pitting corrosion resistance at low chloride concentration compared to low-carbon steel, regardless of the passivation condition. However, at high chloride concentration, low-alloy steel shows higher pitting corrosion resistance due to the formation of Cr-enriched protective rust layer.

Mercury(II) trace detection by a gold nanoparticle-modified glassy carbon electrode using square-wave anodic stripping voltammetry including a chloride desorption step

Gold nanoparticles (AuNPs) were deposited on a glassy carbon (GC) substrate by constant potential electrolysis and characterized by cyclic voltammetry in H2SO4 and field emission gun scanning electron microscopy (FEG-SEM). The modified AuNPs–GC electrode was used for low Hg(II) concentration detection using a Square Wave Anodic Stripping Voltammetry (SWASV) procedure which included a chloride desorption step. The comparison of the obtained results with our previous work in which no desorption step was used showed that this latter step significantly improved the analytical performances, providing a three time higher sensitivity and a limit of detection of 80pM for 300s preconcentration, as well as a lower average standard deviation. The influence of chloride concentration on the AuNPs–GC electrode response to Hg(II) trace amounts was also studied and its optimal value confirmed to be in the 10−2M range. Finally, the AuNPs–GC electrode was used for the determination of Hg(II) in a natural groundwater sample from south of France. By using a preconcentration time of 3000s, a Hg(II) concentration of 19±3pM was found, which compared well with the result obtained by cold vapor atomic fluorescence spectroscopy (22±2pM).

Salt spray corrosion behaviour of new Mg–Al alloys containing Nd or Gd

The influence of chloride concentration on the salt spray corrosion behaviour of new AZ91D and AM50 alloys containing rare earth (RE) elements was evaluated. The corrosion rate of both materials increased with increasing chloride concentration, particularly for NaCl concentrations above 2 wt-%. The addition of Nd or Gd reduced the amount of β-Mg17Al12 phase and resulted in the formation of RE containing intermetallics that were less noble than the Al–Mn inclusions but more noble than the β-Mg17Al12 phase. The latter modifications decreased the corrosion rate of the AM50 alloy by up to 90% but did not give a clear benefit to the corrosion resistance of the AZ91D alloy.

Zinc coordination to the bapbpy ligand in homogeneous solutions and at liposomes: zinc detection via fluorescence enhancement

In this work, the complexation of the bapbpy ligand to zinc dichloride is described (bapbpy = 6,6′-bis(2-aminopyridyl)-2,2′-bipyridine). The water-soluble, colorless complex [Zn(bapbpy)Cl]Cl·2H2O (compound 2·H2O) was synthesized; its X-ray crystal structure shows a mononuclear, pentacoordinated geometry with one chloride ligand in apical position. Upon excitation of its lowest-energy absorption band (375 nm) compound 2 shows intense emission (Φ = 0.50) at 418 nm in aqueous solution, and an excited state lifetime of 5 ns at room temperature. Photophysical measurements, DFT, and TD-DFT calculations prove that emission arises from vibronically coupled Ligand-to-Ligand Charge Transfer singlet excited states, characterized by electron density flowing from the lone pairs of the non-coordinated NH bridges to the π* orbitals of the pyridine rings. Monofunctionalization of the ligand with one long alkyl chain was realized to afford ligand 3, which can be inserted into dimyristoylphosphatidylglycerol (DMPG) or dimyristoylphosphatidylcholine (DMPC) unilamellar vesicles. For negatively charged DMPG membranes the addition of a zinc salt to the vesicles leads to an enhancement of the fluorescence due to zinc coordination to the membrane-embedded tetrapyridyl ligand. No changes were observed for the zwitterionic DMPC lipids, where binding of the Zn ions does not take place. A modest binding constant was found (5 × 10(6) M(−1)) for the coordination of zinc cations to bapbpy-functionalized DMPG membranes, which allows for the detection of micromolar zinc concentrations in aqueous solution. The influence of chloride concentration and other transition metal ions on the zinc binding was evaluated, and the potential of liposome-supported metal chelators such as ligand 3 for zinc detection in biological media is discussed.

Adsorption of corrosion inhibitors (SA, HEDP) using EQCM: chloride effect and synergic behavior

The adsorption of inhibitor molecules, ascorbic acid (SA), and 1-hydroxyethane-1,1-diphosphonic acid (HEDP), was studied using electrochemical quartz crystal microbalance. Adsorption on iron was studied compared with gold in the presence of chloride ions and at E OP and cathodic potential. Each of these parameters significantly affects monolayer adsorption following the Langmuir isotherm. HEDP was adsorbed more rapidly than SA. The novelty in this study concerns the influence of chloride concentration on the inhibition efficiency. Indeed, the rate of inhibition also depends on the concentration ratio of chloride/inhibitor, which is an important factor for the practical implementation of these compounds. Adding a small quantity of chloride ions can increase adsorption rate as well as degree of coverage. Optimum behavior was noted for a HEDP/Cl− ratio about 500. Passivation of the electrode to cathodic potential influenced HEDP adsorption and promoted that of SA. A low adsorption current proportional to the concentration of the inhibitor was recorded. A synergic inhibition by the two molecules was observed for a concentration relationship of 1.16. The study showed that SA was not adsorbed at the interface but its presence made a reduction in lateral tensions possible between adsorbed HEDP, leading to a better coverage.

A Quantitative Study on the Effects of Environment and Microstructure on Pit Initiation in Al-alloys

Potentiostatic testing was employed to examine pit initiation on AA7075-T651 exposed to chloride solutions. The influence of chloride concentration, potential, and temperature on pit initiation was studied. An automated method for counting current transients is presented, and the applicability of potentiostatic testing in Al alloys is generally discussed.

Pitting Corrosion of Zn and Zn-Al Coated Steels in pH 2 to 12 NaCl Solutions

Corrosion behavior of hard zinc, Al (Galfan), and Al alloy (Zincalume or Galvalume) coated steels was studied using cyclic voltammetry and potential scan/hold technique in the presence of 0.10- over a pH range of 2 to 12. Influence of chloride concentration and electrolyte pH on pitting potential values of the above three types of specimens were examined. On the basis of the electrochemical, scanning electron microscopy with energy dispersive X-ray spectroscopy, and chemical equilibria data obtained from hard zinc, a pitting corrosion mechanism involving a series of processes from anion competitive adsorption to penetration to nucleation and growth was proposed.

Influence of chloride concentration on the formation of AOX in UV oxidative system

In this study, the effects of chloride ion concentration and pH on UV oxidation treatment were examined. Acetone and sodium dodecyl sulfate (ABS) were used as organic substances. The treatment efficiencies of these chemicals by UV/H 2O 2 oxidation using a laboratory scale UV-free surface reactor (UV-FSR) with or without Cl − addition at different pH values was compared. Results of this study indicated that Cl − concentration and the chemical structure of the substances are more decisive than pH in the oxidation process. There was no AOX at the start of the experiments but as a result of oxidation a de novo synthesis of AOX was observed, and these AOX de novo compounds were destroyed during the treatment. Treatment was followed by TOC and AOX measurements. Approximately 98% and 95% TOC removal efficiencies were obtained for the treatment of acetone and ABS containing wastewaters, respectively.

The formation of chlorine dioxide in the electrochemical treatment of drinking water for disinfection

There are increased activities in development and application of electrochemical disinfection cells using the natural chloride content for disinfectants production by directly electrolysed water. Unfortunately, the process is insufficiently studied until now and the conditions under which the cells are sold and used are not well controlled. Health risks are probable because limiting concentrations may be exceeded as could be shown in special experiments. One main by-product of drinking water electrolysis is chlorine dioxide that can be formed under several conditions. The present work discusses problems of chlorine dioxide formation and reactions during and after electrolysis. First results are presented, which were obtained in synthetic and real drinking waters using titanium anodes with IrO 2/RuO 2 coatings. Analysis problems and possible mechanisms are discussed. The influence of chloride concentration up to 250 mg L −1, current density (up to 500 A m −2) and other parameters on ClO 2 formation is shown. Chlorine dioxide concentrations in the lower milligram per litre range could be measured.

AOX Formation and Elimination in the Oxidative Treatment of Synthetic Wastewaters in a UV-Free Surface Reactor (6 pp)

Intention, Goal, Scope, Background The effect of chloride concentration and pH on the UV oxidation systems was examined. Phenol and methanol were used as organic substances. The treatment of these chemicals by UV oxidation using a newly developed lab scale pretest UV-Free Surface Reactor (UV-FSR) with and without Cl– addition at different pH values, is evaluated. Results of this study indicated that the Cl– concentration of the water and the chemical structure of the substances is more important than the pH of the water. There was no AOX at the beginning of the experiments, but a de-novo synthesis of AOX was observed during the batch experiments. This is caused by the high chloride content of the wastewaters. It can be supposed that OHradicals oxidize some chloride-ions to form chlorine, which further reacts with organic compounds. During the treatment, these AOX compounds which are produced from the beginning of the reaction are destroyed again. Evaluations of these experiments were done according to TOC and AOX results. Approximately 80% and 99% TOC removal efficiencies were obtained for the treatment of Phenol and Methanol-containing wastewaters, respectively.