Galvanic Cell Research Articles

Insights of mechanism into enhanced removal of Cr(VI) by Ginkgo biloba leaves synthesized bimetallic nano-zero-valent iron/copper

For purpose of green preparation of nano-zero-valent iron and copper (GB-nZVI/Cu), the use of Ginkgo biloba extract as a reducing agent is reported herein. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS) analyzed the properties of nanoparticles. GB-nZVI/Cu exhibited a better Cr(VI) removal performance than nZVI/Cu materials synthesized by apricot leaves (Al-nZVI/Cu) and hawthorn leaves (Hl-nZVI/Cu). GB-nZVI/Cu could remove 97.2% Cr(VI) in 30 min. Low pH and 313 K promoted the reaction while humic acid (HA) had inhibitory effect. The promoting effects of coexisting anions were observed following the order: SO42->HCO3->Cl-. The rate constant K2 increased from 0.0303 to 4.8865 g·mg-1·min-1 as SO42− concentration increased. Na+ and low Mg2+ concentration promoted the removal of Cr(VI) while NO3−, K+, Ca2+ and high Mg2+ concentration had the negative effects. The removal reaction followed the pseudo-second-order kinetic model, with a chemical adsorption as a rate-controlling step. Visual MINTEQ models and mechanism studies showed that the removal of Cr(VI) by GB-nZVI/Cu was a combination of adsorption, reduction and precipitation. The Fe-Cu galvanic cell can accelerate the corrosion of Fe0, enhancing the reduction of Cr(VI). Cu0/Cu(I) could be oxidation into Cu(II) by receiving electrons from Fe3+, resulting in the generation of Fe2+. Cr(III) finally precipitated in the form of FeXCr1−X(OH)3 and Cr(OH)3. GB-nZVI/Cu had superior sedimentation behavior and more Fe2+ production to promote Cr(VI) reduction. GB-nZVI/Cu maintained a better removal performance of Cr(VI) than Al-nZVI/Cu and Hl-nZVI/Cu after five reuses.

Utilization of cylindrical Cu/Fe galvanic cell as an effective method for the removal of humic acids

Utilization of cylindrical Cu/Fe galvanic cell as an effective method for the removal of humic acids

Experimental Investigation of Coupled Transport Mechanisms in a PEM Based Thermoelectric Energy Converter

Thermoelectric energy converters based on galvanic cells (TGC) offer the possibility of direct conversion of low-temperature waste heat into electrical energy and could therefore be a promising approach for an increase in the overall efficiency of energy conversion. Due to an externally applied heat source, a temperature gradient across the electrolyte is induced, leading to a gradient in the chemical potential of the species and an electrical potential difference between the electrodes. The aim of approaching an internal equilibrium state leads to various coupled molecular transport mechanisms taking place in the electrolyte, impacting the open circuit voltage (OCV) and the performance of the TGC. By applying the theory of non-equilibrium thermodynamics (NET) to describe these coupled processes, the interactions that occur can be characterized in more detail. In this work, a polymer electrolyte membrane (PEM)-based TGC with two H2/H2O electrodes of different temperatures and gas compositions is experimentally investigated. By controlling the gradients in temperature and concentration, different impacts on the resulting OCV can be identified. In addition, we present the measured coupling coefficient, representing the singular relation between the transport of the hydrogen ions inside the membrane and the electrical potential difference between the electrodes for a wide variety of working conditions.

PH-Responsive Fluorescent Metal-Organic Framework as a Functional Nanofiller for Smart Coatings.

A zirconium-based UiO-type UiO-66-(OH)2 metal-organic framework@carbon dot composite (Zr-MOF@CD) is synthesized through a facile solvent-free thermal method. The Zr-MOF@CD exhibits pH-responsive fluorescence behavior, which emits blue fluorescence for pH < 9 at an emission wavelength of 470 nm. At pH > 9, the fluorescence color turns from blue to yellow, with the emission behavior at 535 nm. Zr-MOF@CDs can serve as functional nanofillers in the epoxy coating for the fabrication of a smart coating, which can realize coating damage warning and metal corrosion reporting. The blue fluorescence can be observed in the area of coating damage with just a minor scratch. Once the scratch is severe enough to expose the metal substrate, the cathodic reaction of oxygen reduction in the corrosion galvanic cell causes an increased pH, where the emission of yellow fluorescence can be identified. The stable fluorescence response is free from the influence of concentration, time, temperature, and the interfering substance. Zr-MOF@CDs can also serve as nanocontainers for loading with the corrosion inhibitor and realizing the repairing of metal corrosion. The development of the smart coating with dual functions of autonomous reporting and repairing holds great potential to improve the lifetime of metals in various industrial applications.

Enhanced interface heat transfer based on gallium-based liquid metal infiltrated into vertically aligned copper nanowire arrays

Owing to the high aspect ratio and thermal conductivity, copper nanowires have great potential as novel thermal conductivity fillers. However, the thermal conductivity of thermal interface materials (TIMs) prepared by copper nanowires with polymer matrices is low. In contrast, gallium-based liquid metal has a higher thermal conductivity than polymer, while it is difficult to wet copper nanowires with liquid metal to prepare the TIMs. In this study, TIMs with a thickness of 53 µm were prepared by forming a galvanic cell between gallium-based liquid metal and vertically aligned copper nanowire arrays to improve wettability, and the heat transfer performance of the TIMs was experimentally investigated. The results show that the total thermal contact resistance of the composite thermal interface material is as low as 3.20 ± 0.24 mm2K/W. Compared with commercial thermal grease, the total thermal contact resistance is reduced by 86.30 %. The total thermal contact resistance increases with the surface roughness as the actual contact area decreases. In HCl/CuSO4 solution, the wettability of gallium-based liquid metal on the surface of vertically aligned copper nanowire arrays was improved, and the contact angle was 10.1 ± 0.9°. Furthermore, after 360 h of ageing, the total thermal contact resistance of the sample increased by 0.57 mm2K/W. This study provides new directions for designing high-performance TIMs with excellent overall heat transfer properties for the thermal management of electronic equipment.

Iron-carbon micro-electrolysis simultaneously enhanced nutrient and heavy metal removal in constructed wetlands for purifying polluted groundwater with variable hydraulic loadings

Heavy metal and nitrate pollution, as a primary water quality issue in shallow groundwater, is posing a severe threat to public health from drinking groundwater. In this study, iron-carbon (Fe-C) fillers were applied in constructed wetlands (CWs) to enhance the nutrient and heavy metal removal simultaneously, while the interaction of effective nitrate reduction and heavy metals mitigation under variable influent hydraulic loadings was also investigated. Groundwater is not conducive to biological heterotrophic denitrification due to its low dissolved organic matter content. Fe-C fillers can form plentiful microscopic galvanic cells and act as inorganic electron donors to promote the autotrophic denitrification process. The results showed that Fe-C micro-electrolytic CWs showed excellent simultaneous removal of nutrients and heavy metals. The nitrate nitrogen (NO3–-N) removal rate was as high as 75.77% due to the increased autotrophic denitrification process, while the removal of total nitrogen (TN) and total phosphorus (TP) could reach 73.72 % and 89.04% with a low nitrous oxide (N2O) emission of 12.12 μg m-2h−1. Besides, the removal rates of chromium (Cr) and lead (Pb) reached 98.96% and 97.09%, respectively. However, the presence of heavy metals might inhibit denitrification by competing with nitrite for electrons and generating free radicals, which decreased the denitrification by 10.02–39.05% particularly with the increasing of the hydraulic loading. On the other hand, heavy metals promoted TP removal by forming metal phosphate precipitates and complexations with phosphorus. This study provides comprehensive insights into processes and mechanism of simultaneous nutrient and heavy metal removal in CW.

Study on nitrate removal from wastewater by micro-electrolysis and construction of iron-carbon micro-electrolysis reactor (ICMER)

This study explored the potential of using iron-carbon micro-electrolysis (ICMER) to remove nitrate from artificially simulated wastewater. Various factors that mainly influence the removal efficiency of nitrate from wastewater were studied using batch experiments. The results showed that the mixing of iron and activated carbon formed a galvanic cell to effectively remove nitrates at the optimal Fe/C ratio of 3:1 (88.22% for NO3–-N and 33.54% for TN). Moreover, the removal of nitrates was not influenced by the changes in temperature (removal efficiency stabilized within the range of 88.98%-90.26% for the temperatures range of 10-50℃). In addition, the results from the continuous flow ICMER reactor showed that the removal efficiencies of nitrate and TN were 83.77% and 61.66%, respectively, with the Fe/C ratio of 3:1. Coexisting anions showed a significant influence on the removal efficiency of nitrates from wastewater. This study provides a reference for developing ICMER technology to remove nitrates from various wastewater systems.

Uncovering a Kind of Natural Galvanic Cell to Spontaneously Synthesize a Variety of Carbon-Supported Core–Shell Nanoparticles for Efficient Electrocatalysis

Here, we uncover a kind of natural galvanic cell to spontaneously synthesize a variety of McMs′/C NPs for efficient electrocatalysis. In these galvanic cells, the negative and positive electrodes are the owned functional groups (e.g., C–O–C, C–OH, COOH, etc.) and supported noble-metal NPs (e. g., Au, Pt, Pd, etc.) of carbon black, and the electrolyte is the solution of shell precursors. Such galvanic cells are capable of spontaneously synthesizing uniform McMs′/C NPs such as AucPts/C, AucPds/C, AucAgs/C, AucRus/C, PtcAgs/C, PdcRus/C, etc. As an example, as-prepared AucPds/C exhibits over 4-fold specific activity in the electrocatalytic ethanol oxidation compared to referenced Pd/C.

Robust Self‐Catalytic Reactor for CO2 Methanation Fabricated by Metal 3D Printing and Selective Electrochemical Dissolution

AbstractThe methanation of CO2 has been actively pursued as a practical approach to mitigating global climate change. However, the complexity of the catalyst development process has hindered the development of new catalysts for CO2 methanation; as a result, few catalysts are commercially available. Herein, a multifunctional self‐catalytic reactor (SCR) is prepared via metal 3D printing and selective electrochemical dissolution as a method to not only simplify the catalyst development process but also fabricate active catalysts for CO2 methanation. The combination of metal 3D printing and selective electrochemical dissolution is demonstrated as a feasible method to prepare active catalysts for the methanation of CO2 in a short time. In addition, the use of an electrochemical method enables the formation of galvanic cells on the SCR; these cells continuously generate active sites via self‐dissolution during a simple refresh process, resulting in high reusability of the SCR. The proposed method represents a new facile technique to fabricate highly reusable catalysts that exhibit superior performance for CO2 methanation, and the results provide a guideline for preparing metal 3D‐printed catalysts that will satisfy industrial demand.

Frequency of galvanic pair detection of metal structures in the mouth in the absence of galvanic syndrome and pathological changes in the oral mucosa

BACKGROUND: Currently, numerous metal structures are used in dentistry, such as implants, pins, dentures, etc. These structures are often made of various metals and metal alloys with different electrochemical potentials. This circumstance can lead to the appearance of a galvanic cell, consisting of metal structures. In the existing literature, no data reveal the frequency of the detection of galvanic pairs of metal structures in the mouth in the absence of galvanic syndrome and oral mucosal diseases.&#x0D; AIM: To examine the detection frequency of galvanic pairs of metal structures in the mouth in the absence of galvanic syndrome and pathological changes in the oral mucosa.&#x0D; MATERIALS AND METHODS: A survey of 133 patients aged 3387 years was conducted to detect the presence of galvanic pairs of metal structures in the mouth. All patients do not have galvanic syndrome and pathological changes in the oral mucosa. The patients were divided into four age groups: 3344 years old (n = 33), 4559 years old (n = 35), 6074 years old (n = 35), and 7587 years old (n = 30). Electrochemical potentials of metal structures in the mouth were determined according to the method developed at the Department of Therapeutic Dentistry of the E. V. Borovsky Institute of Dentistry of the First Moscow State Medical University named after I.M. Sechenov (Sechenov University). An electrode made of 999 gold was used as an active indicator electrode, which was used to touch metal structures in the mouth during the study. An EHP-1 silver chloride electrode was used as a passive reference electrode. A Fluke 115 multimeter was used as a measuring device.&#x0D; RESULTS: In the group aged 3344 years, galvanic pairs were found in 18%, and they had 5.2 2.1 metal structures. The group aged 4559 years had 7.4 3.5 metal structures in the mouth, and 23% of the participants had galvanic vapors in the oral cavity. In the group aged 6074 years, 26% had galvanic vapors in the oral cavity. In this group, the maximum number of metal structures in the mouth was 7.9 4.1. In the group aged 7587 years, 20% had galvanic pairs of metal structures in the mouth, and they had 5.9 1.8 metal structures in the oral cavity.&#x0D; CONCLUSION: Galvanic pairs of metal structures in the oral cavity were found is 1826% of the participants in different age groups. The share is associated not so much with age but to a greater extent with the number of metal structures in the oral cavity. With the increased number of metal structures, the probability of the appearance of a galvanic pair in the mouth, formed by metal structures with different electrochemical potentials, increases.

Facile synthesis of silver-rhenium nanoparticles with plasmonic and mesoporous properties

Cetyltrimethylammonium bromide (CTAB) capped rhenium (Re0@CTA(aq)) NPs were prepared by using chemical reduction method at room temperature in aqueous solution. The resulting Re0@CTA(aq) sol was utilized as sacrificial template and silver ions (Ag+) for the synthesis of silver-rhenium bimetallic NPs (Ag0-Re0@CTA(aq)) under metal displacement galvanic cell reaction in aqueous solution with CTAB. Surface Plasmon resonance (SPR) band intensity and wavelength maxima of Plasmon band of Ag0-Re0@CTA(aq) depends on the concentration of CTAB. The Plasmon band was blue shifted from 434, 439, 519, 535, 465, and 445 nm, respectively, for 0.0, 0.75, 1.0, 1.25, 1.5, and 2.0 mM of CTAB. Oxidation states, crystalline nature, elemental composition, surface morphology, shape, size, and textural properties of as-prepared silver-rhenium were determined with X-ray photoelectron spectrometry (EDX), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and nitrogen adsorption-desorption isotherm (BET). Fourier transform infrared spectrometry (FTIR), 1H NMR, 13C NMR, and gas chromatography-mass spectrometry (GC-EIMS) analysis were used to establish the capping properties of CTAB. Application of FTIR, 1H NMR, 13C NMR and GC-EIMS analysis shows that the CTAB consistently remains adsorbed on Ag0-Os0 NPs. Optical properties of plasmonic nanomaterials can be tuned by using a suitable concentration of CTAB surfactant.

Effect of the Cu/Mg Ratio on Mechanical Properties and Corrosion Resistance of Wrought Al–Cu–Mg–Ag Alloy

The present study aimed to investigate the influence of magnesium (Mg) on the mechanical properties and corrosion behavior of wrought Al–4Cu–xMg–0.6Ag alloys. The results from Optical Microscope, SEM, XRD analysis, and Thermo-Calc simulation were used to identify the microstructure formed after the aging process. Testing for hardness and tensile strength was conducted, in addition to corrosion testing. It was found that Mg significantly impacts the hardness of the alloys, with a high Mg content (low Cu/Mg ratio) increasing the hardness but reducing the tensile strength and ductility. This study attributed this to the formation of the S phase, which is dependent on both the quantity in the bulk and the size of the phase. The grain size was found to be finer with a higher Mg content, since the particle size inhibits grain growth during the artificial aging process. Counterintuitively, the corrosion activity was reduced in the high-Mg-content alloy due to its large particle size and the reduced galvanic cell effect. This study highlighted the importance of considering the effects of Mg on the mechanical properties and corrosion behavior of Al–Cu–Mg–Ag alloys.

High temperature thermo-chemical properties evolution of NaF-NiF2 system

In Molten Salt Reactor (MSR), Ni based alloys are more suitable for handling of the molten fluoride salts because of formation of corrosive resistive NiF2 layer over the structural material components. A ternary mixture of LiF-NaF-KF (FLiNaK) can be used as coolant salt for transfer of heat from the reactor core. NiF2 layer of the Ni-based alloys shows reactivity towards NaF at reactor operating temperature. NaNiF3(s) is the single complex ternary compound in the NaF-NiF2 system. The compound has been synthesized and characterized. The thermodynamic stability of NaNiF3(s) has been experimentally measured in terms of Gibbs energy of formation using Galvanic cell technique and its measured ΔfG°m(T) was obtained as.ΔfG°m(T) [NaNiF3(s)]/kJ mol−1 = (−1242.9 ± 2.3) + (0.2312 ± 0.0039) × (T/K).The heat capcity and high temperature enthalpy increment was also experimentally measured using DSC and high temperature calorimetric technique, respectively and the values were obtained as.Cp,m(J·mol−1·K−1) = 117.74 + 0.0498 × T −1.07351 × 106/T2(303 ≤ T/K ≤ 828).(HT-H298)(J·mol−1) = −40270.6 + 120.4 × T + 0.0234 × T2+717669.7/T.Effect of oxygen impurity over the stability of the compound has been investigated by calculating the chemical potential diagram of Na-Ni-F-O system. The binary phase diagram of NaF-NiF2 system and the ternary phase diagram of Na-Ni-F2 system has been calculated based on Gibbs energy minimization technique using the experimental thermodynamic data.

Stability Enhancement of Galvanic Redox Potentiometry by Optimizing the Redox Couple in Counterpart Poles.

Potentiometry based on the galvanic cell mechanism, i.e., galvanic redox potentiometry (GRP), has recently emerged as a new tool for in vivo neurochemical sensing with high neuronal compatibility and good sensing property. However, the stability of open circuit voltage (EOC) outputting remains to be further improved for in vivo sensing application. In this study, we find that the EOC stability could be enhanced by adjusting the sort and the concentration ratio of the redox couple in the counterpart pole (i.e., indicating electrode) of GRP. With dopamine (DA) as the sensing target, we construct a spontaneously powered single-electrode-based GRP sensor (GRP2.0) and investigate the correlation between the stability and the redox couple used in the counterpart pole. Theoretical consideration suggests that the EOC drift is minimum when the concentration ratio of the oxidized form (O1) to the reduced form (R1) of the redox species in the backfilled solution is 1:1. The experimental results demonstrate that, compared with other redox species (i.e., dissolved O2 at 3 M KCl, potassium ferricyanide (K3Fe(CN)6), and hexaammineruthenium(III) chloride (Ru(NH3)6Cl3)) used as the counterpart pole, potassium hexachloroiridate(IV) (K2IrCl6) exhibits better chemical stability and outputs more stable EOC. As a result, when IrCl62-/3- with the concentration ratio of 1:1 is used as the counterpart, GRP2.0 displays not only an excellent EOC stability (i.e., 3.8 mV drifting during 2200 s for in vivo recording) but also small electrode-to-electrode variation (i.e., the maximum EOC variation between four electrodes is 2.7 mV). Upon integration with the electrophysiology, GRP2.0 records a robust DA release, accompanied by a burst of neural firing, during the optical stimulation. This study paves a new avenue to stable neurochemical sensing in vivo.

Effects of ultrasound on the CrMnFeCoNi coatings with different TiC contents fabricated by laser cladding

The present study systematically explores the effect of ultrasound on the CrMnFeCoNi + x(TiC) coatings fabricated by laser cladding. The investigations revealed that the microstructure of the CrMnFeCoNi + x(TiC) cladding layers prepared without ultrasonic assistance is mainly columnar dendrites. With the introduction of ultrasound, the columnar dendrites break up and form equiaxed dendrites. The aggregation of TiC is reduced in the 2 wt% TiC cladding layer prepared by ultrasonic assistance relative to that without ultrasonic assistance. On the other hand, increasing the TiC to 4 wt% in the cladding layer resulted in the spreading of TiC in a wider range along the grain boundary upon ultrasonic treatment. Furthermore, the grain size shows no obvious changes and there is no significant textural characteristics in cladding layers prepared with and without ultrasonic assistance. In contrast, the effect of ultrasound on the TiC distribution is minimal in the cladding layer with 10 wt% TiC. Besides, the introduction of ultrasound could effectively reduce the mass wear rate and the friction coefficient of the CrMnFeCoNi cladding layer with different TiC content except that of 10 wt% TiC cladding layer. The large size and small number of TiC particles in ultrasonic-assisted and non-ultrasonic-assisted 10 wt% TiC cladding layers leads to a decrease in the number of forming corrosion galvanic cell and a decrease in the influence on the dislocation density. Therefore, both ultrasonic-assisted and non-ultrasonic-assisted 10 wt% TiC cladding layers exhibite high electrochemical corrosion resistance. The effect of ultrasonic vibration on CrMnFeCoNi cladding layers with different TiC contents can be explained by the influence of TiC on ultrasonic attenuation.

Novel instrumentation for high-impedance electromotive force (EMF) measurements

Instrumentation is reported for measuring electromotive force (EMF) from a high-impedance solid electrolyte-based electrochemical cell. Generally, concentration galvanic cells are used to study the high-temperature thermochemical properties of materials. The thermochemical results are determined by precise measurement of the high-impedance EMF and temperature of the electrochemical cell with suitable user interface software for data acquisition. The data are conditioned and processed using the unique design of the hardware and sent to a computer through the serial port. Online graphical displays of the data, averaging, trend viewing, and storage, are performed using a graphical user interface (GUI). The instrumentation was validated by conducting experiments with different materials using an electrochemical cell and its performance was demonstrated to be on par with commercial instruments. This work has enables low-cost sophisticated EMF measurements for determining the thermochemical properties of materials.

Performance Enhancement of Biobattery from Tropical Almond Paste Using Acetic Acid Addition

&lt;p class="AbstractText"&gt;&lt;span lang="EN-AU"&gt;Biobattery is an alternative energy device that uses organic waste without hazardous chemicals. It is further reported that tropical almond (Terminalia catappa L.) is rich in glucose content, making it a potential electrolyte for a biobattery device, although the power performance is not optimal. Therefore, this research aims to improve the performance of biobattery from tropical almond paste with the addition of acetic acid. Biobattery cells were constructed using the galvanic cell method, while the tropical almond paste as an electrolyte was stored in a box container with a volume of 600 cm³, then attached with copper and zinc metal plate as cathode and anode. Five typical devices of biobattery were made with various acid concentrations of 0%, 10%, 20%, 40%, and 80% which were added to the electrolyte. The results showed a significant enhancement of power performance, from 0.25 mW without any acid up to 1.62 mW with acid addition. The biobattery from tropical almond paste added with acetic acid of 20% had the best performance. Based on the results, the characterization of this device had an open cell voltage of 0.93, and the power curve showed a peak value of 1.62 mW at a current of 3.29 mA, with a stable current lasting up to 200 hr.&lt;/span&gt;&lt;/p&gt;

Mechanism of corrosion and sedimentation of nickel electrodes for alkaline water electrolysis

Nickle is one of the most promising alternatives to noble-metal catalysts in alkaline water electrolysis (AWE). Although Ni exhibits superior stability in alkaline solution, the sediments which have been observed in some situations result in a limited electrolytic efficiency of Ni electrodes. This work was proposed to elucidate the sedimentation mechanism of Ni electrodes via a long-term test in KOH solution. Electrochemical tests and localized electrochemical tests were applied to assess the corrosion behavior of Ni electrodes. The micromorphology and grain orientations of electrodes were investigated by SEM, EDS, EBSD and XPS. The tested anode was found apparently roughened, leaving veinlet-like corrosion textures on the surface, meanwhile pits in several micrometers were found. The collected sediments were composed of elements such as Pb, Sn, Ni, K, O and C. The polarization impedance of the tested anode was 0.4 Ω cm2, which is far lower than that of the as-prepared anode, 56 Ω cm2. In alkaline solution, the galvanic cells formed since the tested anode was found with a positive potential (+13.8 μV) and a negative potential (−7.8 μV) and caused local corrosion. Galvanic corrosion was also observed between the anode and cathode during the electrolysis. By applying an external potential, metallic components of the Ni anode were progressively dissolved and converted to ions. Then the produced ions traversed through the test solution to the cathode side and were reduced to metals precipitating on the cathode. It is believed that anode material exfoliation and ion precipitation jointly contributed to the sedimentation.

Role of 5 wt.% Mg Alloying in Al on Corrosion Characteristics of Al-Mg Coating Deposited by Plasma Arc Thermal Spray Process.

The corrosion of steel structures in coastal areas is a major issue. Therefore, in the present study, the protection against the corrosion of structural steel is carried out by depositing 100 μm thick Al and Al-5 Mg coatings using a plasma arc thermal spray process, immersing them in 3.5 wt.% NaCl solution for 41 days (d). To deposit such metals, one of the best known processes, arc thermal spray, is frequently used, but this process has severe defects and porosity. Thus, to minimize the porosity and defects of arc thermal spray, a plasma arc thermal spray process is developed. In this process, we used normal gas to create plasma instead of argon (Ar) and nitrogen (N2) with hydrogen (H) and helium (He). Al-5 Mg alloy coating exhibited uniform and dense morphology, where it reduced more than four times the porosity compared to Al, where Mg fills the voids of the coating, resulting in greater bond adhesion and hydrophobicity. The open circuit potential (OCP) of both coatings exhibited electropositive values due to the formation of native oxide in Al, while in the case of Al-5 Mg, the coating is dense and uniform. However, after 1 d of immersion, both coatings showed activation in OCP, owing to the dissolution of splat particles from the corner where the sharp edges are present in the Al coating, while Mg preferentially dissolved in the Al-5 Mg coating and made galvanic cells. Mg is galvanically more active than Al in the Al-5 Mg coating. Due to the capacity of the corrosion products to cover the pores and defects, both coatings stabilized the OCP after 13 d of immersion. The total impedance of the Al-5 Mg coating is gradually increased and is higher than the Al, which can be attributed to the uniform and dense coating morphology where Mg dissolves and agglomerates to form globular corrosion products and deposit over the surface, thereby causing barrier protection. The defect bearing corrosion products on Al coating led to the cause having a higher corrosion rate than the Al-5 Mg coating. A total of 5 wt.% mg in the Al coating improved the corrosion rate by a rate of 1.6 times compared to the pure Al in the 3.5 wt.% NaCl solution after 41 d of immersion.

PH-responsive mesoporous silica nanocontainers based on Zn-BTA complexes as stoppers for controllable release of corrosion inhibitors and application in epoxy coatings

A classical strategy of constructing pH-sensitive release system is to encapsulate mesoporous nanoparticles with insoluble complexes such as copper-benzotriazole (Cu-BTA) complex. In this paper, a new capping material, Zn-BTA complex, was adopted to overcome the promoting effect of Cu2+ ions from the decomposition of Cu-BTA complexes on corrosion of mild steel. Mesoporous silica nanoparticles (MSNs) were synthesized, loaded with BTA and then capped with Zn-BTA complexes as stoppers to form MSN-BTA@Zn nanocontainers. The releasing behaviors of BTA at various pH values were investigated, and it was found that MSN-BTA@Zn could achieve on-command release of BTA in response to decrease of pH caused by anodic reaction of corrosion. MSN-BTA@Zn nanocontainers were introduced to epoxy resin to construct stimuli-responsive coating on mild steel substrate. The composite coating with artificial defects shows a distinct stimuli-responsive performance in 3.5 % NaCl, and the incorporation of MSN-BTA@Zn has no impact on the adhesion of the coating to the substrate. The formation of zinc hydroxide compounds in the cathodic zone of galvanic cell makes contribution to the enhancement of corrosion resistance for the coating.