Increasing Chloride Ion Concentration Research Articles

Effect of high-temperature molten salt corrosion on the mechanical properties of stainless steel

The corrosivity of molten salt can be detrimental to the safe operation and longevity of concentrated solar thermal power generation equipment. Additionally, the presence of impurity Cl− can increase corrosion on metal materials, leading to mechanical property degradation. To assess the extent of this effect, the corrosion behaviour of three types of stainless steel (304, 316L, and 347H) in molten salt at high temperatures was studied using the loss-in-weight method and tensile tests. According to the findings, the Rdepths of 304, 316L, and 347H stainless steels are 0.0018 mm/a, 0.0016 mm/a, and 0.0019 mm/a, respectively, resulting in a decrease in elongation of 12.2%, 7.0%, and 3.7% after 720 h of corrosion at 600°C. Furthermore, at a higher temperature of 680°C, the Rdepths of all stainless steels increased, and the elongation decreased by 25.4%, 18.9%, and 13.5%, respectively. Similar corrosion behaviour was observed in 347H stainless steel with increased chloride ion concentration. However, the yield strength and tensile strength of stainless steel did not exhibit significant changes under different experimental conditions. The corrosion mechanism of metal alloys in molten salt is mainly due to the selective corrosion of Cr and its dissolution into molten salt in the form of ions.

The Effects of Cl− and selected deoxidizers on the high temperature corrosion electrochemistry of alloy 690 in nuclear steam generator water

ABSTRACT The heat transfer tube in a steam generator serves as a critical heat exchange component in the primary and secondary loops of pressurized water reactor (PWR) nuclear power plants. The corrosion resistance of the heat transfer tube material directly influences the longevity of PWR nuclear power plants. This study investigated the electrochemical corrosion properties of 690 alloy (UNS N06690) in a simulated secondary water environment of PWR, focusing on different chloride ion concentrations and combinations of deoxidizers. The findings reveal a gradual decrease in the corrosion potential of 690 alloy, accompanied by an increase in self-corrosion current and a progressive reduction in the passivation range, ultimately leading to its disappearance as chloride ion concentration rises from 0 μg·L−1 to 500 μg·L−1. Moreover, the impedance value of the inner film exhibits a declining trend with increase of chloride ion concentration. Conversely, the resistance value of the outer film remains relatively stable while the size and spacing of oxide particles on the surface of the 690 alloy continuously increase. This observation suggests that chloride ions primarily influence the formation of the inner passivation film, which in turn determines the corrosion resistance of the 690 alloy. Notably, the performance of the 690 alloy is similar when the deoxidizer combination is ammonia(NH3)+erythorbic acid(ERA) or NH3+hydrazine(N2H4), demonstrating the ability to form a relatively complete passivation film and exhibit improved corrosion resistance compared to NH3+N-isopropyl hydroxylamine, additionally, when the deoxidizer combination is NH3+N2H4, the 690 alloy exhibits lower self-corrosion current density across different chloride ion concentrations, indicating enhanced corrosion resistance.

Effect of chloride binding and sulfate ion attack on the chloride diffusion in calcium sulfoaluminate-based material under seawater environment

The diffusion of chloride ions in reinforced concrete under the seawater environment will affect the physical or mechanical properties and durability. Sulfate ions also influence the diffusion of chloride ions by generating expansion products through physical and chemical reactions. Further research on the effects of chloride binding and sulfate ion attack on chloride ion diffusion will deepen the understanding of concrete failure mechanism. In this paper, a quaternary blend based on calcium sulfoaluminate (CSA) cement was prepared and laboratory immersion tests were conducted in artificial seawater with varying salt concentrations. Initially, chloride ion concentration measurements and XRD tests were conducted at different corrosion ages and salt concentrations. Subsequently, the chloride binding properties of CSA-based materials was quantified through the analysis of chloride ion concentration and the phases of hydration products. Meanwhile, the corrosive effect of sulfate ions on chloride ion diffusion was determined corresponds to the content of expansive hydration products. Furthermore, numerical simulations were employed to evaluate the impact of sulfate ion corrosion, chloride binding, and their combined effects on chloride ion diffusion, and the results were compared with free chloride ion concentration (Cf). The results indicate that the total chloride ion concentration (Ct) exhibits a linear relationship with increasing salt concentrations of seawater in CSA-based materials. Meanwhile, the bound chloride ion concentration (Cb) follows a logarithmic growth pattern. The chloride binding rate experiences a linear decline with the increase of chloride ion concentration in the artificial seawater. Additionally, the relationship between Cf and Cb or Ct can be described using different isothermal adsorption models for the CSA-based materials. Among these models, the Langmuir model is suitable for characterizing the relationship between Cf and Cb, while the Freundlich model is suitable for describing the relationship between Cf and Ct. Furthermore, it is noteworthy that sulfate ion attack and chloride binding exert nearly equivalent effects on the diffusion of chloride ions in CSA-based materials at short corrosion age and low chloride ion concentration. However, the corrosive impact of sulfate ions gradually evolves into the dominant factor in the progression of corrosion over time and the increase in seawater salt concentration.

Microstructure and Chlorine Ion Corrosion Performance in Bronze Earring Relics.

Chlorine ions play an important role in the corrosion of bronzeware. This study employs techniques such as XRD, OM, SEM, EBSD, and electrochemical testing to analyze the microstructure, crystal structure, chemical composition, and corrosion performance of bronze earrings unearthed at the Xindianzi site in Inner Mongolia. The results indicate the presence of work-hardened structures, including twinning and equiaxed crystals, on the earrings' surface. With an increase in chloride ion concentration in NaCl solutions from 10-3 mol/L to 1 mol/L, the corrosion current density of the bronze earrings increased from 2.372 × 10-7 A/cm2 to 9.051 × 10-7 A/cm2, demonstrating that the alloy's corrosion rate escalates with chloride ion concentration. A 3-day immersion test in 0.5% NaCl solution showed the formation of a passivation layer of metal oxides on the earrings' surface. These findings underscore the significance of the impact chloride ions have on the corrosion of copper alloys, suggesting that activating the alloy's reactive responses can accelerate the corrosion process and provide essential insights into the corrosion mechanisms of bronze artifacts in chloride-containing environments.

Effect of maintenance environment on the mechanical property and pore structure of cement paste mixed by seawater

This study aims to examine the effects of macroscopic mechanical properties and pore structure of cement paste mixed with seawater and explore the relationship between pore structure and macroscopic properties. The changeable law of mechanical properties and pore microstructure of hardened cement paste under seawater mixing is methodically investigated based on the compressive and flexural strengths using X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) tests. The relationship between the fractal dimension of the pore structure of cementitious materials and the concentration of chloride ions in simulated seawater, the curing age, and the fly ash dose was obtained based on the thermodynamic fractal model. The obtained results reveal that with the increase in chloride ion concentration of the simulated seawater, the compressive and flexural strengths of the samples substantially grow in the pre-maintenance period, and the strength of the samples tends to stabilize at the age of 28 days. For the case of the chloride ion concentration of 1.3%, the compressive strength of the cement slurry exhibits a growth of 24.08%, 24.83%, and 28.81% compared to the control cement sample after curing at 5 °C, 20 °C, and 50 °C for 3 days, respectively. Additionally, the flexural strengths in order are 41.86%, 46.57%, and 38.89% higher than those of the control group. The interaction of Cl- with C3A, C4AF, or AFm in seawater mixed at high-temperature to generate Friedel's salt stimulated the volcanic ash reaction of fly ash, promoted the generation of C-S-H gels, and improved the internal pore structure of cementitious materials. The results indicate that at 50 °C curing, the most probable pore diameter of cement paste with 1.3% chloride ion concentration is 39.51% less than that of the control cement sample, and its harmless pores are 23% higher than that of the control group. At 5 °C curing, the total specific pore volume of cement paste with 1.3% chloride ion concentration is 30.18% less than that of the control cement sample, and the total specific pore volume is 22.9% less than the control group for the fly ash content of 25%. The obtained results reveal that there exists a fairly low correlation between the fractal dimension of the pore surface area of the cement paste and porosity, compressive strength, and flexural strength. However, the achieved correlation with the mean pore diameter, median pore diameter, and pore surface area is good, which are all above 75%. The fractal dimension fitting curve of high-temperature curing possesses a range of singular points.

Prediction of interference current of buried pipeline and study on corrosion of Q235A steel

Interference current will cause severe electrochemical corrosion to buried pipes. However, the interference current flowing into the buried pipeline cannot be directly measured, and the influence of interference current on the corrosion of the buried pipeline cannot be directly observed. In this paper, the combined analysis methods of finite element analysis, partial least square method and electrochemical measurement technique are used to predict the interference current of buried pipeline and to study the effect of dynamic interference current and chloride ion concentration on the corrosion of Q235A steel. The prediction results show that increasing the input variables of the prediction model and changing the position of the input variables can effectively improve the accuracy of the model. Electrochemical measurements show that an increase in chloride ion concentration increases the corrosion current density in the polarization curve of Q235A steel and decreases the capacitive reactance arc radius in the electrochemical impedance spectroscopy. In addition, on the basis of the rail-to-ground potential monitoring points in the actual project, the number of rail-to-ground potential monitoring points was increased to improve the prediction accuracy of the buried pipeline interference currents, which indicates that the analysis method is an effective way to monitor and evaluate the influence of stray currents on the corrosion of buried pipelines.

Phototransformation of tetrabromobisphenol A in saline water under simulated sunlight irradiation

The widespread use of halogenated flame retardants in recent years has led to the accumulation of TBBPA in water, which may cause potential harm to living organisms. The phototransformation of the flame retardant TBBPA in alkaline saline water under simulated sunlight irradiation was investigated. The effects of abiotic factors such as the initial concentration of TBBPA, chloride ion concentration, solution pH, inorganic anions and cations, dissolved organic matter (DOM) were studied. The results showed that the phototransformation rate of TBBPA accelerated with the decrease of the initial concentration of TBBPA, the increase of chloride ion concentration and solution pH. The scavenging experiments showed that •OH, 1O2, O2•- and 3TBBPA* all participated in the phototransformation of TBBPA. The presence of NO3−, CO32−, SO42−, Mg2+, Ca2+, Fe3+ and fulvic acid (FA) all inhibited the phototransformation of TBBPA in the present study. The phototransformation products of TBBPA were detected by liquid chromatography-mass spectrometry (LC-MS), and the phototransformation pathways were proposed. This is the first report on the photo-induced generation of halogen exchange products from TBBPA in saline solutions, which will contribute to a better understanding of the environmental behavior and risks of BFRs in water.

Investigation of Electrochemical Corrosion Behaviour of 6082 Aluminum Alloy under Simulated Deicing Agent Conditions

In this study, the aluminum alloy of 6082 with different treatment processes (T1 and T6) was tested in simulated artificial deicing agent solution. The polarization curves show that the alloy suffered from pitting attack, the corrosion resistance of extruded sample (T1) is lower than that of forged sample (T6) in the same medium solution. With the increase of chloride ion concentration, the corrosion current density of T1 and T6 samples increased, the maximum corrosion depth increased, and the corrosion resistance of alloy samples decreased. The morphology on the polarized alloys show that the the surface of T1 sample revealed a higher number of pits. And the difference of corrosion resistance between T1 and T6 is closely related to the difference of microstructure.

Thermodynamic Analysis of Trace Cobalt(II) Extraction from Cobalt Chloride Aqueous Solution Using Cyanex 272 in Kerosene

In this study, it was researched that the extraction of Co(II) from CoCl2 aqueous solutions using Cyanex 272 (bis(2,4,4-trimethylpentyl) phosphonic acid) in kerosene and determined the effects of the equilibrium pH value, extractant concentration and chloride ion concentration on the extraction of cobalt at different temperatures. The results indicate that the distribution ratio of cobalt increases as the equilibrium pH value, extractant concentration and extraction temperature increase. However, the cobalt distribution ratio decreases as the chloride ion concentration increases. We calculated the equilibrium constants (AH9, AG9, and AS9) for a range of temperatures and investigated the relationship between AG9 and T. The extraction reaction of cobalt was determined to be an endothermic reaction; thus, raising the temperature was beneficial to the reaction.

Saltwater corrosion behaviour of equal channel angular pressed AZ80/91 Mg alloys

In this study, AZ80/91 Mg alloys were used to comprehend the electrochemical corrosion behaviour of coarse-grained and fine-grained Mg alloys in different concentration of NaCl solution as well as in the marine environment. The inadequate studies of the corrosion response of ECAPed AZ80 and AZ91 Mg alloy in a different environment were noticed. Accordingly, the current research presents and compares the corrosion behaviour of AZ80/91 Mg alloys in 2.5 wt% NaCl, 3.5 wt% NaCl solution and Natural Sea Water. Influence of corrosion media on coarse and fine-grained AZ80/91 Mg alloys was discussed in the results and discussion section. Corrosion attack of AZ80/91 Mg alloys under the above environment, increased with increase in chloride ion concentration and decreased with the ECAP passes.

Effect of copper slag fine aggregate on corrosion processes and behavior in reinforced concrete prism specimen

This paper reports the result of experimental on the resistance to chloride diffusion and steel corrosion of concrete mixtures. A series of tests were performed to investigate the effect of copper slag as partial replacement of fine aggregate on corrosion processes and behavior in prism specimens. Chloride migration tests in steady-state were executed at the age of 28 and 91 days in accordance with Japan Society of Civil Engineers (JSCE) G571-2003 to determine the diffusion coefficient of chloride ions permeated through concrete specimens. In addition, some electrochemical tests were carried out through the repeated wet and dry (NaCl 10%) cycles up to 1 year to examines the probability of corrosion of steel bars in concrete, corrosion current density, and the rate of oxygen permeability. Based on the chloride migration test, which was obtained from the cumulative increase of chloride ion concentration, the results indicate that concrete with a longer curing period achieved lower chloride-ion concentration, thus suggesting that there is an increase in the resistance of concrete against chloride attack. The chloride penetration depth and distribution of chloride content in CUS prism specimens after exposure to wet and dry cycles for one year are almost similar to those of the OPC specimens. Thus, the durability performance of CUS concretes with respect to the resistance against chloride ingress was comparable to that of OPC concrete. Besides that, it is generally recognized that the incorporation of fly ash in blended cement by its the pozzolanic reaction of fly ash improves concrete protection against chloride-induced corrosion of steel bars by reducing its diffusivity and the rate of oxygen permeability.

In-Vitro Degradation of Hollow Silica Reinforced Magnesium Syntactic Foams in Different Simulated Body Fluids for Biomedical Applications

This article reports the mechanical and biocorrosion behaviour of hollow silica nanosphere (SiO2) reinforced (0.5–2 vol.%) magnesium (Mg) syntactic foams. Room temperature tensile properties’ characterization suggests that the increased addition of hollow silica nanospheres resulted in a progressive increase in tensile yield strength (TYS) and ultimate tensile strength (UTS) with Mg-2 vol.% SiO2 exhibiting a maximum TYS of 167 MPa and a UTS of 217 MPa. The degradation behaviour of the developed Mg-SiO2 syntactic foams in four different simulated body fluids (SBFs): artificial blood plasma solution (ABPS), phosphate-buffered saline solution (PBS), artificial saliva solution (ASS) and Hanks’ balanced saline solution (HBSS) was investigated by using potentiodynamic polarization studies. Results indicate that corrosion resistance of the Mg-SiO2 syntactic foam decreases with increasing chloride ion concentration of the SBF. Mg-1.0 vol.% SiO2 displayed the best corrosion response and its corrosion susceptibility pertaining to corrosion rate and polarisation curves in different SBF solutions can be ranked in the following order: ABPS > PBS > HBSS > ASS. The surface microstructure demonstrated the presence of a better passivated layer on the syntactic foams compared to pure Mg. The observed increase in corrosion resistance is correlated with intrinsic changes in microstructure due to the presence of hollow silica nanospheres. Further, the effect of corrosive environment on the degradation behaviour of Mg has been elucidated.

The Influence of Chloride Ion Concentration on the Localized Corrosion of E717 Magnesium Alloy

The localized corrosion behavior of E717 magnesium alloy immersed in chloride-containing electrolyte is investigated using an in situ scanning vibrating electrode technique (SVET) coupled with time-lapse imaging. It is shown that initiation of localized corrosion in chloride-containing electrolyte is characterized by the appearance of discrete local anodes, corresponding with the leading edges of dark, filiform-like features, which combine with time to produce a mobile anodic front. The size and growth rate of these features are highly dependent on the chloride ion concentration of the electrolyte. SVET-derived current density maps reveal that the corroded surface left behind the anodic front is cathodically activated, where cathodic current density values progressively decline with increasing distance away from the anodic leading edge. The intensity of localized anodes is highly dependent on the chloride ion concentration, where progressively higher local anodic current density values are observed with increasing chloride ion concentration along with progressively higher rates of volumetrically determined hydrogen evolution. Breakdown potential, measured using time-dependent free corrosion potential transients and potentiodynamic polarization at neutral and elevated pH, respectively, is shown to vary with the logarithm of chloride ion concentration, and the time for localized corrosion initiation is progressively increased with decreasing chloride concentration. From the combination of results that are presented herein, the underlying reasons for the influence of chloride ion concentration on the localized corrosion characteristics of E717 alloy will be discussed.

CO2 Corrosion of Carbon Steel: The Synergy of Chloride Ion Concentration and Temperature on Metal Penetration

This paper investigates the synergy of chloride ion concentration and temperature on the general and pitting corrosion of carbon steel in CO2-saturated environments. Experiments were conducted over 168 h in different concentrations of NaCl brines (1 wt%, 3.5 wt%, and 10 wt%) and temperatures (30°C, 50°C, and 80°C) with the aim of elucidating the combined effect of changes in chloride ion concentration and temperature on overall metal degradation, taking into consideration general and pitting corrosion. This also includes a correlation with the formation and properties of FeCO3 corrosion products. Linear polarization resistance was implemented to monitor the electrochemical responses. Corrosion product characteristics and morphologies were studied through a combination of scanning electron microscopy and x-ray diffraction. Pitting corrosion evaluation was conducted through the application of 3D surface profilometry to study pit geometries such as the depth and diameter. The results show that general and pitting corrosion are strongly correlated to the synergistic effects of changing chloride ion concentration and temperature in carbon steel as a result of their combined influence on ferrite (Fe) dissolution and FeCO3 formation. This represents a paradigm shift from the already established mechanisms on chloride ion and temperature effects on passive alloys such as stainless steel. Increasing chloride ion concentration and temperature up to 10 wt% NaCl and 50°C to 80°C, respectively, is observed to increase the rate of Fe dissolution and formation of semiprotective FeCO3 corrosion products, leading to the increased manifestation and severity of pitting corrosion. The results also show that a “threshold chloride concentration” exists at 30°C, above which there is no significant increase in corrosion rate. However, such “threshold effects” were not observed at higher temperatures evaluated in the range of chloride concentration considered in this study.

The Acceleration of Pitting Corrosion of AISI 304 Stainless Steel by Ultraviolet Light Illumination in Acidic Chloride Solution

The influence of ultraviolet light (UV, λ = 254 nm) illumination on pitting of AISI 304 stainless steel was investigated using critical pitting chloride concentration (CPCC) measurement. In a H2SO4 solution with a gradually increased chloride ion concentration, the CPCC was measured for AISI 304 samples at 0.65 VSCE and 30 °C under different illumination conditions. Direct UV illumination significantly reduced the CPCC value from 0.286 ± 0.018 M (in the dark) to 0.087 ± 0.008 M. Both the passivation process in pure H2SO4 solution and pit growth in acidic chloride solution were affected by UV illumination. The passive film formed in 0.1 M H2SO4 solution with UV illumination (in which a smaller ratio of metal oxides to metal hydroxides was observed) had a lower corrosion resistance than that formed in the dark, indicating the decreased stability of passive film after UV illumination. In addition, UV illumination also accelerated the pit growth rate of 304 samples in acidic chloride solution. After the CPCC tests, lacy cover and rough edges were observed with pits formed in the dark, while no lacy cover was present for pits developed under UV illumination.

Removal of the Rhodamine B Dye at Ti/Ru0.3Ti0.7O2 Anode Using Flow Cell System

The electrochemical oxidation of the Rhodamine B dye (Rh-B) was carried out using dimensionally stable type anode (DSA, Ti/Ru0.3Ti0.7O2). The work was performed using the electrochemical flow cell system. The effect of several operating factors, such as supporting electrolytes, current density, electrolysis time, temperature, and initial concentration of Rh-B dye, were investigated. The UV-visible spectroscopy and chemical oxygen demand (COD) measurements were conducted to monitor the removal and degradation of Rh-B. The best color removal achieved was found to be 98.3% after 10 min applying 3.9 mA·cm−2 as a current density using 0.07 mol·L−1 of NaCl. Meanwhile, the highest COD removal rate (93.0%) was obtained for an applied current density of 3.9 mA·cm−2 as the optimal operating condition after 180 min reaction time, with 2.98 kW h·m−3 as energy consumption. This shows that the best conditions for color removal are not certainly the same as those for the COD removal. The rises in the concentration of NaCl, and applied current increased the Rh-B color removal rate. The decline in Rh-B dye concentration followed pseudo-first-order kinetics. The obtained values of apparent rate constant were increased by increasing chloride ion concentration. It is concluded that the electro-oxidation on DSA electrode using a flow cell is a suitable process for the removal of Rh-B dye in aqueous solutions.

Spectroscopic Analysis of Chloride Ion-induced Structural Change of Bacillus Amyloliquefaciens α-Amylase

The structural change of Bacillus amyloliquefaciens α -amylase (Ba α -amylase) induced by chloride ion was studied by fluorescence spectra, Fourier-transformation infrared (FT-IR) spectroscopy and circular dichroism (CD) spectroscopy. It was found that when chloride ion concentration was below 20.0 mM, the Ba α -amylase was activated by increasing chloride ion concentration; when chloride ion concentration was over 20.0 mM, the biological activity of Ba α -amylase was inhibited by increasing chloride ion concentration. The spectroscopic analyses illustrated that the change in Ba α -amylase biological activity was caused by the alteration in secondary structure of Ba α -amylase. When chloride ion showed activation effect to Ba α -amylase, part of the random coils in Ba α -amylase gradually transformed to α -helix and β -sheet with increasing chloride ion concentration and the Ba α -amylase transited from relatively disordered conformation to relatively ordered one. Whereas when chloride ion showed inhibition effect on the biological activity of Ba α -amylase, part of α -helix and β -sheet in Ba α -amylase gradually transformed to random coil with increasing chloride ion concentration and the Ba α -amylase went back from the relatively ordered conformation to the relatively disordered one. This work shows the dependency of change in biological activity to alteration in secondary structure of protein molecule, which may provide some useful information in the actual application and exploration on action mechanism of proteins. The biological activities of Ba α-amylases increased quickly with the increase of chloride ion concentrations under 20.0 mM that the change was caused by transforming random coil to α-helix and β-sheet; the relative activities of Ba α-amylases decreased slowly with the increase of chloride ion concentrations exceed 20.0 mM that the change was caused by transforming α-helix and β-sheet to random coil. When chloride ion concentration was 20.0 mM, the biological activity of Ba α-amylases was the maximum.

Influence of chloride ion adsorption on the kinetics and mechanism of Ru(NH3)63+/2+ electrode reactions

In the experiment, we prepared metal electrodes with sub-micron to nanometer for the scanning electrochemical microscopy to study the kinetics of Ru(NH3)63+/2+ redox system. The rates of reduction of Ru(NH3)6(NO3)3 were found essentially independent of the nature of the electrode material, but mildly dependent upon chloride ion concentration. We observed that the ‘outer-sphere’ reactant of Ru(NH3)6(NO3)3 reduced at relatively slower rates in low-chloride solutions. This phenomenon appears to be compatible with the expected variations in a ligand-bridged mechanism in which the electrostatic repulsions among the specifically adsorbed chloride anions that dominate would have an adverse influence on the adsorption of inner-sphere cationic reactants and thus cause a decrease in the reaction rate. However, as 0.1 M supporting electrolyte KCl was added into the target solution, a significant increase in the reaction rate was measured as a result of the ionic double-layer effect. Cationic complexes will experience the same electrostatic attraction from adsorbed chloride anions as will outer-sphere reactants. It is suggested that the reaction pathway of Ru(NH3)63+ reduction can change from the anion-bridged inner-sphere to the outer-sphere with increasing chloride ion concentration up to 0.1 M.

An experimental case study on corrosion characterization of Cu46Zr40Ti8.5Al5.5 metallic glass

In the present work, a novel Cu46Zr40Ti8.5Al5.5 metallic glass is synthesized by melt spun technique and investigated for corrosion behavior at various molar concentrations in acidic, neutral and alkaline solutions (at different pH levels), using potentiodynamic polarization experiment and electrochemical impedance spectroscopy (EIS). Surface morphology and composition analysis after corrosion test were carried out by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Results indicate that corrosion resistance decreases with increase in chloride ion concentration in case of acidic and neutral media. However, in case of alkaline solution, corrosion resistance is found to be similar for pH 8 and pH 10, but is observed to decrease at pH 12. Melt spun sample was highly susceptible to pitting corrosion at higher molarity in acidic and neutral solution as observed from SEM analysis. EDS results indicate depletion of galvanically active metals (Al > Ti > Zr) from pit interior. Furthermore, an attempt has been made to study the influence of Al in corrosion behavior of the sample.

Effects of electrolyte thickness, chloride ion concentration, and an external direct current electric field on corrosion behaviour of silver under a thin electrolyte layer

ABSTRACTEffects of electrolyte thickness, chloride ion concentration, and an external direct current electric field (DCEF) on the corrosion behaviour of silver under a thin electrolyte layer (TEL) were investigated using electrochemical and surface techniques. The results indicate the corrosion rate of silver increases with the decrease of TEL thickness and the increase of chloride ion concentration. Moreover, an interesting conclusion was drawn that the corrosion rate of silver near the positive plate of DCEF first increases and then decreases with the increase of electric field intensity. In a DCEF, different polarisation behaviours of silver at different positions were attributed to the differences of the local corrosion environment.