Influence Of Chloride Ion Concentration Research Articles

Influence of Chloride Ion Concentration on Corrosion Behavior of WC–MgO Composite

The influence of chloride ion (Cl−) concentration on the corrosion mechanism of WC–MgO composites has been studied in this work. The results suggest that the corrosion resistance of WC–MgO composite decreases first and then increases with the increase in Cl− concentration. Solution conductivity and dissolved oxygen content are the main influence factors. The solution conductivity determines the charge transfer process, and the dissolved oxygen determines the cathodic oxygen absorption reaction. The corrosion characteristic is typical pitting corrosion. Meanwhile, the corrosion mechanism contains an oxidation process of the WC matrix and the dissolution destruction of the MgO toughening phase. The formation of the WO3 corrosion layer hinders the general corrosion to protect the inner material. However, the dissolution of MgO induces the initiation of pitting. The local alkaline caused by MgO dissolution promotes the dissolution of the WC matrix, which leads to the expansion of pitting.

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.

Copper Tube Pitting Corrosion Product and Evaluation of Influence of Chloride Ion Concentration in Hot Water Environment

Copper Tube Pitting Corrosion Product and Evaluation of Influence of Chloride Ion Concentration in Hot Water Environment

Influence of chloride ion concentration and temperature on the corrosion of Cu–Al composite plates in salt fog

In this work, the effects of temperature and chloride ion concentration were evaluated for the corrosion behavior of Cu–Al composite plates exposed to salt spray. There were three diffusion layers at the interface between Cu and Al, which were Al4Cu9, AlCu and Al2Cu, respectively. Corrosion only appeared on the diffusion layers and the aluminum, amongst which Al2Cu was the most vulnerable to corrosion, AlCu and Al were the second most vulnerable while the corrosion resistance of Al4Cu9 was second to the Cu. When the concentration of NaCl was lower than 3 wt%, the increased concentration had an obvious effect on the mass loss of the corrosion for the Cu–Al composite plates. The kinetic constant of corrosion increased with the increasing NaCl concentration. When the concentration of NaCl increased from 1 wt% to 3 wt%, the kinetic constant of corrosion increased by 31 times. With the concentration of NaCl increasing to 5 wt%, the kinetic constant of corrosion was 4.6 times that of 3 wt% by weight. In addition, the kinetic constant of corrosion was affected by temperature. With an increase of temperature, the kinetic constant of corrosion initially increased, and then decreased. The kinetic constant of corrosion reached its maximum value at 45 °C. Finally, the results of electrochemical testing showed that an increase of the chloride ion concentration (CIC) accelerated the corrosion of Cu–Al composite plates, and the corrosion attack was the worst under 45 °C.

Mapping the Galvanic Corrosion of Three Coupled Metal Alloys Using Coupled Multielectrode Array: Influence of Chloride Ion Concentration.

The galvanic corrosion behavior of three metal alloys commonly used in water desalination plants was investigated using coupled multielectrode arrays consisting of aluminum-brass (HAl77-2), titanium alloy (TA2), and 316L stainless steel (316L SS). The three electrode types were coupled galvanically and arranged in different geometric configurations. Their corrosion behavior was characterized as a function of the chloride concentration. The potential and current distributions of the three-electrode coupling systems display electrochemical inhomogeneity. Generally, the aluminum-brass wires are anodic versus the titanium alloy and stainless steel. The titanium alloy acts as a primary cathode, and the 316L SS acts as a secondary cathode. The corrosion rate of aluminum-brass depends on the concentration of chloride ion, with a maximum corrosion rate at a chloride concentration of 2.3 wt %. In terms of geometrical arrangements, when the anodic HAl77-2 wires are located on the edge and are connected to the 316L SS wires in the coupling system, the main anodic area enlarges, especially in the area adjacent to the 316L SS wires. When the HAl77-2 wires are located between (in the middle of) the two other types of wires, the corrosion rates are higher than the corrosion rates observed from the other two geometrical arrangements.

Photo-assisted electrochemical degradation of simulated textile effluent coupled with simultaneous chlorine photolysis.

The influence of chloride ion concentration during the photo-assisted electrochemical degradation of simulated textile effluent, using a commercial Ti/Ru0.3Ti0.7O2 anode, was evaluated. Initially, the effect of applied current and supporting electrolyte concentration on the conversion of chloride ions to form reactive chlorine species in 90min of experiment was analyzed in order to determine the maximum production of reactive chlorine species. The optimum conditions encountered (1.5 A and 0.3moldm(-3) NaCl) were subsequently employed for the degradation of simulated textile effluent. The efficiency of the process was determined through the analysis of chemical oxygen demand (COD), total organic carbon (TOC), of the presence of organochlorine products and phytotoxicity. Photo-assisted electrochemical degradation was more efficient for COD and TOC removal than the electrochemical technique alone. With simultaneous UV irradiation, a reduced quantity of reactive chlorine was produced, indicating that photolysis of the chlorine species led to the formation of hydroxyl radicals. This fact turns a simple electrochemical process into an advanced oxidation process.

Influence of chloride ion concentration on immersion corrosion behaviour of plasma sprayed alumina coatings on AZ31B magnesium alloy

Abstract Corrosion attack of aluminium and magnesium based alloys is a major issue worldwide. The corrosion degradation of an uncoated and atmospheric plasma sprayed alumina (APS) coatings on AZ31B magnesium alloy was investigated using immersion corrosion test in NaCl solutions of different chloride ion concentrations viz., 0.01 M, 0.2 M, 0.6 M and 1 M. The corroded surface was characterized by an optical microscope and X-ray diffraction. The results showed that the corrosion deterioration of uncoated and coated samples were significantly influenced by chloride ion concentration. The uncoated magnesium and alumina coatings were found to offer a superior corrosion resistance in lower chloride ion concentration NaCl solutions (0.01 M and 0.2 M NaCl). On the other hand the coatings and Mg alloy substrate were found to be highly susceptible to localized damage, and could not provide an effective corrosion protection in solutions containing higher chloride concentrations (0.6 M and 1 M). It was found that the corrosion resistance of the ceramic coatings and base metal gets deteriorated with the increase in the chloride concentrations.

Influence of Chloride Ions on Corrosion of Modified Martensitic Stainless Steels at High Temperatures Under a CO2Environment

The influence of chloride ion concentration on the passivation film and corrosion product film of martensitic stainless steels (SS) (13% Cr, modified 13% Cr-1% Mo, modified 13% Cr-2% Mo, and 15% Cr...

Effect of chloride ion level on the corrosion performance of MAO modified AZ31 alloy in NaCl solutions

Microarc oxidation coatings were fabricated on AZ31 magnesium alloy in the electrolyte of sodium phosphate. Potentiodynamic polarization and electrochemical impedance spectroscopy tests were employed to investigate the electrochemical corrosion behavior. The corroded surface was characterized by an optical microscope and X-ray diffraction. The influence of chloride ion concentration on the corrosion resistance of microarc oxidation coated AZ31 alloy is discussed. The corrosion current density enlarged ratio and the charge transfer resistance reduced ratio indicated that the extent of the corrosion damage of microarc oxidation coated AZ31 alloy is much higher when chloride ion concentration is greater than 5%. A corrosion mechanism related to the effect of chloride ion concentrations on the corrosion behavior is proposed.

Influence of chloride ion concentration on the corrosion behavior of Al-bearing TRIP steels

The effect of a systematic increase of chloride ion concentration on the electrochemical corrosion behavior of two types of Al-bearing TRIP steels (T 1 and T 2) was studied in aqueous NaCl solutions. Several electrochemical techniques were used comprising open circuit potential measurements, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Chloride concentration has a critical influence on the corrosion rate of the two tested steel samples. For both steels the corrosion rate first increased with increasing chloride content up to a certain critical concentration (CC), and then decreased in solution with chloride level higher than the threshold value. TRIP steel T 1 microalloyed with Nb and Cr as compared to steel T 2 not containing these two elements, exhibited lower corrosion rate and smaller CC value, indicating better corrosion resistance to chloride attack, albeit the Al content in T 2 is 220 times higher than that in T 1. This is because Nb alloyed with TRIP steel likely enhances the formation on the surface of a stable rust layer enriched with other passivating elements Al, Cu, Cr and Ni, which has higher corrosion resistance and hence improve greatly the passive performance of the TRIP sample. The ac impedance data are in good agreement with the OCP and dc polarization measurements. Surface examinations via scanning electron microscope confirmed well the obtained results.

Influence of chloride ion concentration on the electrochemical corrosion behaviour of plasma electrolytic oxidation coated AM50 magnesium alloy

The electrochemical degradation of a silicate- and a phosphate-based plasma electrolytic oxidation (PEO) coated AM50 magnesium alloy obtained using a pulsed DC power supply was investigated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in NaCl solutions of different chloride ion concentrations viz., 0.01 M, 0.1 M, 0.5 M and 1 M. The surface of the PEO coated specimens after 50 h of immersion/EIS testing was examined by optical microscopy and scanning electron microscopy. The results showed that the corrosion deterioration of PEO coated magnesium alloy in NaCl solutions was significantly influenced by chloride ion concentration. The silicate-based coating was found to offer a superior corrosion resistance to the magnesium substrate than the phosphate-based coatings in lower chloride ion concentration NaCl solutions (0.01 M and 0.1 M NaCl). On the other hand both these PEO coatings were found to be highly susceptible to localized damage, and could not provide an effective corrosion protection to Mg alloy substrate in solutions containing higher chloride concentrations (0.5 M and 1 M). The extent of localized damage was observed to be more with increase in chloride concentration in both the cases.

Influence of chloride ion concentration and temperature on the corrosion of Mg–Al alloys in salt fog

The influence of temperature and chloride concentration on the corrosion behaviour of Mg–Al alloys exposed to salt fog was evaluated. Corrosion attack increased with decreasing aluminium content in the alloy and increasing Cl − concentration and temperature. The effect of Al–Mn inclusions, which revealed several stoichiometries and were up to 300 mV more noble than the magnesium matrix, was only noticeable in the early stages of corrosion of the AZ31 alloy. Aluminium segregation and β-phase distribution were the main controlling factors for the AZ80 and AZ91D alloys, the latter being more susceptible to variations in the saline concentration.

Studies on the Influence of Chloride Ion Concentration on the Corrosion Behavior of ZSMX Magnesium Alloy

The paper presented reveals the influence of chloride ion concentration on the corrosion and electrochemical behavior of new ZSMX wrought magnesium alloy in NaCl solution. The experimental techniques used include potentiodynamic polarization tests. The corrosion rate usually increased with the increase in chloride ion concentration. This result can be explained by the distribution of intermetalics.

Influence of chloride ion concentration and temperature on the electrochemical properties of passive films formed on a superduplex stainless steel

Polarization measurements were conducted to monitor the corrosion behavior of superduplex stainless steel ASTM A995M-Gr.5A/EN 10283-Mat#1.4469(GX2CrNiMo26-7-4) when exposed to a) an electrolyte containing 22,700 parts per million (ppm) of chloride ions at seven different temperatures and b) an electrolyte at 25 °C and different chloride ion concentrations (5800, 22,700, 58,000 and 80,000 ppm of Cl −). The polarization curves indicate that the passive films formed are only slightly affected by NaCl concentration, but the pitting potential decreases drastically increasing the temperature, in particular > 60 °C. The image analysis of the microstructure after potentiodynamic polarization showed that the pitting number and size vary in function of the temperature of the tested medium. Nyquist diagrams were determined by electrochemical impedance spectroscopy to characterize the resistance of the passive layer. According to Nyquist plots, the arc polarization resistance decreases increasing the temperature due to a catalytic degradation of the oxide passive films.

A study of the influence of chloride ion concentration on the corrosion behavior of carbon steel in phosphate high‐temperature boiler water chemistries

PurposeThis paper sets out to study the corrosion of No. 20 carbon steel without film and with films of different qualities in high‐temperature boiler water with different Cl− concentrations.Design/methodology/approachThe static simulated experiment in high‐pressure autoclave and the surface analysis methods of EPMA and XRD were carried out to study the corrosion effect.FindingsUnder the following conditions: T=360±3°C, pH = 9.40±0.10, cO2<0.020 mg/l, the density of pitting corrosion on specimens without a protective film increased with the increase of CCl− content, while CCl− was > 0.2 mg/l. The film on specimens with integral films would not dissolve observably even until the CCl− concentration was as high as 0.8 mg/l. Films with corrosion pits would begin dissolving when the Cl− concentration reached 0.4 mg/l. The main constituents of the oxidative films in the gas and liquid phases both were Fe3O4.Practical implicationsIn order to prevent carbon steel from corroding in boiler water containing Cl− under conditions of low‐phosphate and low‐sodium hydroxide treatment, the concentration of Cl− should be strictly controlled.Originality/valueIt was found that the presence of excessive Cl− in boiler water accelerated the corrosion of No. 20 carbon steel and the maximum permissible concentration of Cl− under the conditions (temperature and pressure) of sub‐critical drum boilers was 0.2 mg/l. The research results can provide theoretical guidelines for preventing the facilities of power plants from corroding.

Voltammetric studies on the electrochemical determination of methylmercury in chloride medium at carbon microelectrodes

Electroanalytical techniques have been used to determine methylmercury at low levels in environmental matrices. The electrochemical behaviour of methylmercury at carbon microelectrodes in a hydrochloric acid medium using cyclic, square wave and fast-scan linear-sweep voltammetric techniques has been investigated. The analytical utility of the methylmercury reoxidation peak has been explored, but the recorded peak currents were found to be poorly reproducible. This is ascribed to two factors: the adsorption of insoluble chloromercury compounds on the electrode surface, which appears to be an important contribution to hinder the voltammetric signal of methylmercury; and the competition between the reoxidation of the methylmercury radical and its dimerization reaction, which limits the reproducibility of the methylmercury peak. These problems were successfully overcome by adopting the appropriate experimental conditions. Fast-scan rates were employed and an efficient electrochemical regeneration procedure of the electrode surface was achieved, under potentiostatic conditions in a mercury-free solution containing potassium thiocyanate—a strong complexing agent. The influence of chloride ion concentration was analysed. Interference by metals, such as lead and cadmium, was considered. Calibration plots were obtained in the micromolar and submicromolar concentration ranges, allowing the electrochemical determination of methylmercury in trace amounts. An estuarine water sample was analysed using the new method with a glassy carbon microelectrode.

Studies on the influence of chloride ion concentration and pH on the corrosion and electrochemical behaviour of AZ63 magnesium alloy

Abstract Magnesium-based light alloys belong to a class of structural materials with increasing industrial attention. Magnesium alloys show the lowest density among the engineering metallic materials, low cost and large availability. As a consequence, this light alloys have a promising future. The paper presented reveals the influence of chloride ion concentration and pH on the corrosion and electrochemical behavior of AZ63 magnesium alloy in NaCl solution. The experimental techniques used include immersion studies and potentiodynamic polarization tests. The corrosion rate was very high in highly acidic solutions (pH 2) as compared to that in other solutions. The corrosion rate usually increased with the decrease in pH and the increase in chloride ion concentration. But the quantity of the increase in corrosion rate was different at separate pH and concentration regions. The corrosion potential usually shifted to more negative values with the increase in concentration of chloride ions and the decrease in pH of solution.

Studies on the influence of chloride ion and pH on the corrosion and electrochemical behaviour of AZ91D magnesium alloy

The influence of chloride ion concentration and pH on the corrosion and electrochemical behaviour of die-cast and ingot-cast AZ91D alloy have been studied with a focus on the stability of microconstituents in these environments. The experimental techniques used include immersion studies, potentiodynamic polarization, X-ray diffraction and optical and scanning electron microscopy. The corrosion rate for the ingot and die-cast was very high in highly acidic solutions (pH 1–2) as compared to that in neutral and highly alkaline solutions (pH 4.5–12.0), and the rate increased with chloride ion concentration at all pH levels. In general, the die-cast showed a lower corrosion rate at all pH values and chloride ion concentrations. The open circuit corrosion potential shifted to more negative (more active) values with increase in concentration of chloride ions. Corrosion morphologies revealed more attack on primary α and eutectic α with increasing chloride concentration. In highly acidic conditions, corrosion attack was found on β (Mg17Al12) and eutectic α phase (α regions with higher Al content) while at pH 12.0 the ingot exhibited a pitting type of morphology. The corrosion product consisted of magnesium hydroxide, fallen β particles and magnesium–aluminium oxide; the amount of each component was found to be a function of chloride ion concentration and pH.

Pit propagation rate on the 2024 and 6056 aluminium alloys

The susceptibility to pitting corrosion of the 2024 T351 and of the 6056 T6 aluminium alloys was evaluated by determining the mean pit propagation rate of these materials in different conditions. The influence of chloride ion concentration and that of the polarisation potential were studied. Whichever the material, the mean pit propagation rate varied linearly with the logarithm of the chloride concentration. Plotting the variation of the pit propagation rate with polarisation potential, a significant difference appeared between the two alloys. This difference was related to the metallurgical structure of the materials.

Dichloro(1,4,8,11-tetraazacyclotetradecane)manganese(III) chloride: cis–trans isomerisation evidenced by infrared and electrochemical studies

The isomers cis- and trans-dichloro(1,4,8,11-tetraazacyclotetradecane)manganese(III) chloride have been synthesized and characterised. An isomerisation of the type cis-MnIII → trans-MnIII was observed by IR spectroscopy. Recrystallisation of the cis species gave systematically crystals of the trans derivative. The crystal structure of the latter complex has been determined. An electrochemical study of the trans-manganese(III) complex in dimethyl sulfoxide revealed a rare trans → cis isomerisation reaction which proceeds through an electrochemical step–chemical step mechanism. The overall first-order rate constant, kiso, for this isomerisation was determined by simulation of the chronoamperometric data. Supplementary electrochemical information for the trans-manganese(III) isomer was obtained through simulation of the cyclic voltammograms over a large range of scan rates. No influence of chloride ion concentration was observed as determined by cyclic voltammetry using an internal chloride standard, [N(PPh3)2]Cl. The cyclic voltammogram of the cis-dichloro(1,4,8,11-tetraazacyclotetradecane)manganese(II) generated in situ displays the usual cis → trans isomerisation which also occurs via an electrochemical step–chemical step mechanism.