Local Electrochemical Techniques Research Articles

Electrochemical characterization of localized corrosion mechanism of ALD Al2O3-coated copper for microelectronic application

To achieve performance and reliability in microelectronics devices, copper interconnections must be protected from aggressive environment during the manufacturing process and throughout the life of the devices. Atomic Layer Deposition Al2O3 thin films has been used as a compatible layer with key integration process steps, as well as being corrosion-resistant in neutral media. However, electrochemical tests in aggressive environment have revealed that the alumina prematurely failed to protect copper from localized corrosion. In this study, local and global electrochemical techniques have been employed to evaluate the reactivity of copper at multiple scales and to elucidate the underlying corrosion mechanisms.

Electrochemistry of 2D-materials for the remediation of environmental pollutants and alternative energy storage/conversion materials and devices, a comprehensive review

This review article explores into the complicated relationship between electrochemistry and 2D materials, exploring their mutual influences and the consequential advancements in energy conversion, storage, and environmental applications. Electrochemical reactions, manifested through oxidations and reductions at submerged electrodes, form the linchpin connecting the electrochemistry of 2D materials with their practical utility. Various electrochemical cell topologies are investigated for their role in enhancing material flexibility, operational states, energy conversion efficiency, and device design adaptability. The comprehensive discussion extends to diverse applications, emphasizing the pivotal roles of 2D materials in environmental remediation, alternate energy storage and conversion, and chemical reactivity. Noteworthy applications include pollutant detection, adsorption and absorption of pollutants, elimination of both organic and inorganic pollutants, and photocatalytic degradation. The review also addresses materials synthesis via electrochemical processes, detailing functionalization, handling, and deposition techniques. Particular focus is directed towards local electrochemical techniques enabling the analysis and local alteration of 2D materials. Moreover, this paper concludes the article published in the recent years with this topic and most significant trends observed in 2022 and 2023 with electrochemistry of materials for the remediation of environmental pollutants. While the trends of article publishing increased from 2020 to 2023 with topic alternative energy storage/conversion materials. Finally, offering a comprehensive overview of the synergistic relationship between electrochemistry and 2D materials and their transformative potential in sustainable technologies. Broader contextThe decreasing availability of energy resources and the contamination of the environment are two significant worldwide concerns that need immediate attention. The focus on 2D materials and associated technologies is important for the efficient conversion of solar energy into chemical energy. These materials have diverse applications in fields such as energy (e.g., water splitting), synthesis (e.g., production of valuable chemicals and N2 reduction), and the environment (e.g., CO2 reduction and environmental remediation). Furthermore, Electrochemical energy storage and conversion (EESC) technologies are widely acknowledged as the most viable solutions to address the escalating energy crisis and environmental degradation because to their exceptional energy efficiency and little environmental footprint. Currently, there have been several reports discussing the use of 2D-materials in energy applications and wastewater treatment. However, there is a lack of comprehensive reviews that summarize the electrochemistry of 2D-materials, their preparation strategies, modification techniques, and related properties. Furthermore, there is a need for detailed analysis of the progress in applying 2D-materials for environmental pollution remediation, electrocatalytic performance, energy storage, and conversion technologies and devices. In this paper, we systematically and comprehensively review the electrochemistry of 2D-materials and innovatively analyze the design principles and difficulties of 2D-materials. We discussed comprehensively the remediation of environmental pollutants through 2D-materials in water treatment fields such as photocatylsts, adsorption/absorption and dyes removal as an entry point and provide an in-depth knowledge and outlook on the current status and development potential of specific applications of energy storage and conversion materials and devices.

Top-down nanostructured multilayer MoS2 with atomically sharp edges for electrochemical hydrogen evolution reaction

Cost-efficient and readily scalable platinum-free electrocatalysts are crucial for a smooth transition to future renewable energy systems. Top-down activation of MoS2 promises the production of sustainable hydrogen evolution electrocatalysts from the Earth-abundant molybdenite ore. Here, the deterministic nanopatterning of multilayer MoS2 with numerous zigzag edges is explored as a pathway to enhance hydrogen evolution reaction (HER). Nanopatterned single-nanosheet MoS2 electrodes are assessed by two highly localized electrochemical techniques: selected area voltammetry (with lithography-defined regions of electrode-electrolyte contact) and Scanning ElectroChemical Microscopy (SECM). The nanopatterning effect is the most pronounced after prolonged electrochemical cycling in an acidic electrolyte. The electrocatalytic hydrogen evolution activity of edge-enriched electrodes is dramatically enhanced: the maximum electrochemical current density (jmax) achieved at -510 mV vs. reversible hydrogen electrode (mVRHE) is increased by two orders of magnitude, reaching >300 mA⋅cm−2. Both the η10 and η100 overpotentials are significantly reduced as well. Meanwhile, pristine MoS2 shows just ≈6 times jmax increase (≈30 mA⋅cm−2) after the very same cycling. The increased electrocatalytic activity comes with electrode morphology degradation, evidenced by ex-situ scanning electron microscopy. SECM directly visualizes stronger HER activity in the regions with densely located zigzag edges. Intense white light illumination significantly boosts HER on MoS2 electrodes due to the photo-enhanced MoS2 conductivity. These results improve the understanding and reveal the limitations of MoS2-based electrocatalytic water splitting.

Contribution of Oxygen Reduction to Mg Corrosion: Experimental Evidence By Electrochemical Microprobes

Unravelling the mechanisms of magnesium corrosion is vital for establishing reliable research methodologies, developing new alloys and predicting magnesium degradation behaviour. Hydrogen evolution reaction is widely regarded as by far the main cathodic process during corrosion of magnesium. Hence, tracing the amount of released hydrogen was thought to be a reliable measure of magnesium degradation rate. Recently, experimental evidences obtained by different methods have been presented by several groups that oxygen reduction (ORR) is important secondary cathodic reaction during Mg corrosion [1-8]. For model galvanic couple Al-Cu-Mg, oxygen consumption on the surface of Mg along with that on Cu was observed by using oxygen sensing microoptode [1]. A simultaneous measurement of local current density by scanning vibrating electrode technique (SVET) and local oxygen concentration by oxygen sensing microoptode found a strong oxygen consumption at the active corrosion sites on the surface of commercially pure Mg in NaCl electrolyte [2]. Then, the evidence for the varying contributions of ORR to the total cathodic process on Mg alloys during atmospheric and aqueous corrosion was presented based on newly developed respirometric methods [3-5]. While around 10% of the total cathodic current was ascribed to ORR during aqueous corrosion, up to 60% of the total corrosion process was shown to be due to the ORR contribution during simulated atmospheric corrosion with wet-dry cycles. Nanoparticle-based O2 imaging was used to map decreased O2 concentration at the interface of several Mg alloys exposed to simulated body fluids [6].High ORR rate on a slowly corroding ultra-high-purity Mg (UHP-Mg) in NaCl electrolyte was shown in our recent work [7]. Comparing that with lower ORR rate for faster corroding commercial purity Mg (CP-Mg), the rate of ORR was found to depend on the growth rate of Mg(OH)2 , which is the main corrosion product of Mg in the simple saline solution. The formation of Mg(OH)2 impeded the diffusion of oxygen from bulk electrolyte to metal interface, preventing metallic Mg substrate from the interaction with oxygen. The distribution of local concentration of dissolved gaseous H2 and O2 assessed by amperometric Clark-type micorprobes at the interface of UHP-Mg and CP-Mg demonstrated the inverse relationship between HER and ORR, and supports the finding that diffusion-controlled ORR highly depends on the barrier property of corrosion products on the surface [8]. The contribution of ORR current to total cathodic current reached 29.1% for UHP-Mg, while only 0.9% for CP-Mg after 1 hour of immersion in NaCl solution. The contribution of ORR decreases with immersion time, due to the impeded access of dissolved O2 to Mg interface caused by thickening of Mg(OH)2 layer. A numerical model was developed considering the mixed potential diagram and measured local oxygen concentration. REFERENCES: [1] D. Snihirova, M. Taryba, S.V. Lamaka, M.F. Montemor, Corrosion inhibition synergies on a model Al-Cu-Mg sample studied by localized scanning electrochemical techniques, Corrosion Science, 112 (2016) 408-417.[2] E.L. Silva, S.V. Lamaka, D. Mei, M.L. Zheludkevich, The Reduction of Dissolved Oxygen During Magnesium Corrosion, ChemistryOpen, 7 (2018) 664-668.[3] M. Strebl, S. Virtanen, Real-Time Monitoring of Atmospheric Magnesium Alloy Corrosion, Journal of The Electrochemical Society, 166 (2019) C3001-C3009.[4] M. Strebl, M. Bruns, S. Virtanen, Editors’ Choice—Respirometric in Situ Methods for Real-Time Monitoring of Corrosion Rates: Part I. Atmospheric Corrosion, Journal of The Electrochemical Society, 167 (2020) 021510.[5] M. Strebl, M.P. Bruns, G. Schulze, S. Virtanen, Respirometric In Situ Methods for Real-Time Monitoring of Corrosion Rates: Part II. Immersion, Journal of the Electrochemical Society, (2021).[6] B. Zeller-Plumhoff, A.R. Akkineni, H. Helmholz, D. Orlov, M. Mosshammer, M. Kühl, R. Willumeit-Römer, M. Gelinsky, Oxygen-sensitive nanoparticles reveal the spatiotemporal dynamics of oxygen reduction during magnesium implant biodegradation, NPJ Materials Degradation, 6 (2022) 95.[7] C. Wang, D. Mei, G. Wiese, L.Q. Wang, M. Deng, S.V. Lamaka, M.L. Zheludkevich, High rate oxygen reduction reaction during corrosion of ultra-high-purity magnesium, NPJ Materials Degradation, 4 (2020) 42.[8] C. Wang, W. Xu, D. Höche, M.L. Zheludkevich, S.V. Lamaka, Exploring the contribution of oxygen reduction reaction to Mg corrosion by modeling assisted local analysis, Journal of Magnesium and Alloys, 11 (2023) 100-109. ACKNOWLEDGEMENTS: C. Wang, Wen Xu, thank China Scholarship Council for the funding, grants no. 201806310128 and 201908510177

Localized corrosion evaluation of newly developed stainless-steel alloys in chloride medium through dynamic and localized micro electrochemical techniques

Novel Fe–Cr SS alloys were fabricated by alloying with 0, 0.10 and 0.20 wt-% Sn respectively to investigate the effect of the Sn addition on the microstructure, passive characteristics and localized corrosion behavior in chloride medium at room temperature. The advanced scanning micro-electrochemical techniques along with the traditional electrochemical methods were used for in-depth investigations. Potentiodynamic and potentiostatic test results exhibited that the addition of Sn in SS alloys increased the resistance against pitting corrosion in NaCl medium. The acquired dynamic impedance data confirmed the effective electrochemical stability of the alloy SS3 (SS with 0.20 wt-% Sn) at applied anodic potential, suggesting the presence of a compact and stable passive film in Sn containing alloys, which contributed to their improved localized corrosion resistance in chloride solution. The scanning electrochemical microscopic results corroborated that the alloy SS3 remained stable even after 24 h of exposure and displayed no noticeable surface heterogeneity. A reduced anodic current density in scanning vibrative electrode technique mapping images was observed even after 24-h of exposure in alloy SS3 compared to other samples, indicating that the anodic metal dissolution was successfully obstructed by forming a compact and dense passive film on this alloy.

Probing passivity of corroding metals using scanning electrochemical probe microscopy

AbstractPassive films are essential for the longevity of metals and alloys in corrosive environments. A great deal of research has been devoted to understanding and characterizing passive films, including their chemical composition, uniformity, thickness, porosity, and conductivity. Many characterization techniques are conducted under vacuum, which do not portray the true in‐service environments passive films will endure. Scanning electrochemical probe microscopy (SEPM) techniques have emerged as necessary tools to complement research on characterizing passive films to enable the in situ extraction of passive film parameters and monitoring of local breakdown events of compromised films. Herein, we review the current research efforts using scanning electrochemical microscopy, scanning electrochemical cell microscopy (or droplet cell measurements), and local electrochemical impedance spectroscopy techniques to advance the knowledge of local properties of passivated metals. The future use of SEPM for quantitative extraction of local film characteristics within in‐service environments (i.e., with varying pH, solution composition, and applied potential) is promising, which can be correlated to nanostructural and microstructural features of the passive film and underlying metal using complementary microscopy and spectroscopy methods. The outlook on this topic is highlighted, including exciting avenues and challenges of these methods in characterizing advanced alloy systems and protective surface films.

Elucidating Degradation Mechanisms of Silicon‐graphite Electrodes in Lithium‐ion Batteries by Local Electrochemistry

AbstractThe integrity of the solid electrolyte interphase (SEI) formed on the negative electrode of lithium‐ion batteries (LIB) is especially critical for the performance of next‐generation LIBs comprising silicon‐carbon based electrode materials. The protecting character of the SEI is compromised due to volume expansion and shrinking during de/intercalation of Li ions leading to irreversible changes upon long‐term cycling. Scanning electrochemical microscopy (SECM) is proposed as local electrochemical technique to investigate the degradation mechanisms of advanced negative electrodes. The impact of charge/discharge cycling on the SEI properties on Si−C electrodes was investigated, and the sensitivity of SECM successfully reveals inhomogeneities at an early stage of the cycling already at about 5 cycles. Macroscopic EIS measurements and evaluation of the coulombic efficiency may result in misleading interpretations of degradation. SECM is demonstrated to be a powerful and complementary technique for revealing μm‐heterogeneities in the SEI surface reactivity after a few charge/discharge cycles.

Kinetics of corrosion reactions on press hardened steel in atmospheric conditions under thin electrolyte films

Steels with high mechanical performance are prone to hydrogen embrittlement and environmental assisted cracking. Under atmospheric corrosion conditions, the source of hydrogen can be the steel corrosion process itself or galvanic coupling with a metallic coating. Electrochemical behaviour of Press Hardened Steel (PHS) under electrolyte films of different thicknesses using local electrochemical techniques was studied on a fundamental level. Scanning Vibrated Electrode Technique (SVET) was applied to study the evolution and localization of the corrosion process during PHS immersion in NaCl electrolyte. Kelvin Probe (KP) was used as a reference electrode to obtain cathodic and anodic polarization curves on PHS surfaces which were covered by thin electrolyte films (60 to 500 µm) of 0.1 M NaOH and 0.6 M NaCl. For both electrolytes, a strong increase in the oxygen reduction rate due to the decreasing of electrolyte thickness has been clearly demonstrated. Data are correlated well with a theoretical plot determined by Nernst-Fick equation. The influence of the rust layers on the kinetics of corrosion reactions under thin electrolyte films was investigated using KP.

Effect of micro-galvanic corrosion on corrosion fatigue cracking of the weld joint of high strength bridge steel

The local electrochemical and corrosion fatigue cracking behavior of the weld joint of Q690qE high-strength bridge steel was investigated in simulated marine environment. It reveals the weld joint was vulnerable to corrosion fatigue failure in polluted marine atmosphere with the corrosion fatigue life considerably lower than that of parent metal. The micro-galvanic corrosion effect between CGHAZ and WM played a dominant role in the corrosion fatigue failure of the weld joint, leading to the final fracture mostly at CGHAZ. The micro-galvanic corrosion was caused by Volta potential variation among various subzones, which was evidenced by local electrochemical techniques.

Effect of pH on the structure and corrosion protection properties of sol-gel coatings

In this work, effect of pH on the structure and corrosion protection properties of sol-gel coatings were investigated, with a special focus on a broad pH range (pH = 1–10) of sol synthesis process. Viscosity, molecular weight, particle size measurements of sols and structural analysis of sol-gel coatings show the highest condensation degree in pH = 4 samples. Electrochemical, localized electrochemical techniques and morphology characterization demonstrate the best corrosion resistance of pH = 4 coatings. Results reveal that high condensation degree results in a compact and stable three-dimensional sol-gel network with high crosslinking density and less silanol content, providing highly effective corrosion protection.

Corrosion mechanism of Ti-6Al-4V morse taper dental implants connected to 316 L stainless steel prosthetic abutment

The aim of this work was to investigate the effect of galvanic coupling between stainless steel AISI 316 L abutment type Morse taper and implant made of ASTM F1108–14 Ti-6Al-4V alloy. The assembly of the two alloys was carried out using mechanical imbrication by means of successive strikes at 0.05 J force onto the abutment inserted in the implant along the centerline. Corrosion attack at the interface of the alloys was evaluated according to the number of strikes used for joining the parts. Corrosion resistance was evaluated for the samples by open circuit potential measurements as function of time and scanning vibrating electrode technique (SVET) and scanning ion selective electrode technique (SIET) in phosphate buffer solution with pH adjusted to 3.0, and into which hydrogen peroxide was added to simulate tissue inflammatory conditions. Samples were evaluated at the cross and longitudinal sections. Results indicated that the number of strikes used in assembling affected corrosion susceptibility. The lowest amount of corrosion products was associated to the highest number of strikes used. The corrosion resistance was related to the characteristics of the crevice between the implant and the abutment. • Galvanic corrosion between Ti grade V dental implants and AISI 316 L prosthetic abutment was investigated. • Localized attack susceptibility increased with the number of strikes to connect the Ti grade V dental implant and the AISI 316 L abutment. • Local electrochemical techniques were very useful in evaluating the corrosion of the coupled dental implant and prosthetic abutment.

Bacterial Biofilm Probed by Scanning Electrochemical Microscopy: A Review

AbstractBacterial biofilm, a highly structured community with developmental processes from cell adherence to highly dense biofilms, is of critical concern in many industries. Investigations of parameters mediating biofilm formation, interactions between bacterial species, and parameters governing biofilm stability are quite important for understanding mechanism of biofilm formation. Scanning electrochemical microscopy (SECM), a local electrochemical technique using a microelectrode as its probe, can monitor microbe interactions in situ via detection of small molecules or biochemical cues with spatial and temporal resolution. In this review, we summarize the recent advances in biofilm research using SECM. First, we introduce the applications and potential biochemical cues of biofilms. Then, we classify the applications based on the bacterial species of interest, focusing on SECM to study key biochemical cues and highlighting underlying metabolic processes involved in biofilm formation. Finally, we discuss the challenges and limitations given the complexity and diversity of biofilms for future SECM studies.

Early biomimetic degradation of Mg-2Ca alloy reveals the impact of β-phases at the interface of this biomaterial on a micro-scale level

Despite several studies on Mg-Ca alloys as bone implants, the understanding of its early degradation in the first hours of immersion is still lacking. To overcome this gap, advanced localized electrochemical techniques were used to study the corrosion onset of Mg-2Ca alloy 2 h upon immersion. The presence of the nobler β-phase induced Mg dissolution from the matrix, an event supporting the positive response of osteoblast stem cells. This, together with apatite precipitation within the corrosion layer highlights the potential of Mg-2Ca for bone implants. The data gathered in this work contribute to tailoring the design of new Mg-Ca alloys.

Evaluation of oxygen consumption at biologically active surfaces using scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) is a local electrochemical analysis technique, which performs scanning of the sample by ultramicroelectrode (UME) [1]. The result of measurement usually is current, which depends on the electrochemical properties of the surface of interest. The errors can be observed if UME geometry is not ideal [2,3]. This happens after UME polishing or breaking after contact with the sample surface. And the aim of this research was to evaluate oxygen consumption at biologically active surfaces using scanning electrochemical microscopy. That is why the oxygen consumption at the surface of interest with UME of different geometry was evaluated in this work. The model results were compared with experimental data. The computational experiment was performed with the SECM model using diffusion equations in the COMSOL program. This model could be further improved to measure diffusion rates with different probe geometries and coefficients.

Highly protective polyolefin coating modified with ceria nano particles treated with N,N,N',N'-Tetrakis(2-hydroxyethyl)ethylenediamine for corrosion protection of carbon steel

A polyolefin coating was modified with cerium oxide nanoparticles treated with N,N,N',N'-Tetrakis(2-hydroxyethyl)ethylenediamine (THEEDA) as corrosion inhibitor for corrosion protection of carbon steel. Electrochemical Impedance Spectroscopy tests carried out in 0.05 M NaCl revealed low-frequency impedance modulus around 1012 Ω cm2 for the modified coating without significant changes after three months of immersion. The self-healing ability of modified coating was studied by combining different localized electrochemical techniques, namely localized impedance spectroscopy (LEIS), the scanning vibrating electrode technique (SVET), and scanning fiber-optic dissolved oxygen microsensor. This comprehensive study confirmed the ability of ceria nanoparticles treated with THEEDA to mitigate corrosion thanks to the synergistic protective role of ceria nanoparticles and THEEDA that inhibit both cathodic and anodic activities, respectively.

COMPREENDENDO OS MECANISMOS DE CORROSÃO DE LIGAS DE Al-Cu-Li: UMA INVESTIGAÇÃO ATRAVÉS DE TÉCNICAS ELETROQUÍMICAS GLOBAIS E LOCAIS

ON THE CORROSION MECHANISMS OF Al-Cu-Li ALLOYS: AN INVESTIGATION USING GLOBAL AND LOCAL ELECTROCHEMICAL TECHNIQUES. In this study, the corrosion mechanism of an Al-Cu-Li alloy manufactured by two different treatment routes (T3 and T851) was evaluated by immersion and electrochemical tests in solutions containing chloride ions (Cl-). For both alloys, the formation of cavities on the surface was associated with micrometer-sized intermetallics (IM’s), however, in addition to this attack, the alloy submitted to T851 treatment also presented an attack called severe localized corrosion (SLC), caused by the preferential attack to the nanometric T1 (Al2CuLi) phase. The electrochemical concepts involved in these two types of attacks were discussed. During the IM’s corrosive process, whereas the O2 reduction occurred over the IM’s, the Al dissolution is favored around the particle, forming trenching and cavities (with 2 and 6 mm of depth). On the other hand, the mechanism associated with the SLC is related to the formation of a differential aeration cell followed by the evolution of H2, with greater depth of attack penetration (8 and 35 mm). Additionally, by the use of the Scanning Vibrating Electrode Technique (SVET), it was concluded that the higher anodic currents observed for the T851 temper were related to the relation between the anodic area (Aa) and the cathodic area (Ac).

Corrosion protection of the AA2198‐T8 alloy by environmentally friendly organic‐inorganic sol‐gel coating based on bis‐1,2‐(triethoxysilyl) ethane

In this work, a surface coating composed of organic‐inorganic hybrid sol‐gel based on bis‐1,2‐(triethoxysilyl) (BTSE) ethane was applied on AA2198‐T8 samples, and its effect on corrosion resistance was investigated and compared with that of a chromate layer formed in a solution with hexavalent chromium ions. The corrosion resistance of BTSE coated samples was evaluated by immersion tests in sodium chloride solution (0.005 mol/L NaCl) and monitored by global electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and local electrochemical techniques such as scanning vibrating electrode technique (SVET) and scanning electrochemical microscopy (SECM). The formed coating layers were characterized by X‐ray photoelectron spectroscopy (XPS). The results pointed out that the BTSE is an effective alternative coating for corrosion protection of new generation Al‐Cu‐Li alloys and could replace chromates obtained in toxic and carcinogenic CrVI containing solutions leading to improved corrosion protection.

Cerium phosphate-based inhibitor for smart corrosion protection of WE43 magnesium alloy

Ce(DEHP)3 (cerium tri(bis(2-ethylhexyl)phosphate)) is proposed as a self-healing corrosion inhibitor for WE43. The use of Ce(DEHP)3 in a 3.90 ± 0.54 µm hybrid epoxy-silane coating led to an improvement of the coating barrier properties. The presence of the inhibitor increased the corrosion resistance, and Electrochemical Impedance Spectroscopy tests carried out in 0.5 M NaCl revealed low frequency impedance modulus (0.01 Hz) around 109 Ω∙cm2. The pH-dependant self-healing effect of Ce(DEHP)3 was evidenced by localized electrochemical techniques, which revealed inhibition of corrosion propagation in artificial defects and decreased net cathodic current densities compared to an unmodified reference coating. Protective behaviour of Ce(DEHP)3 was related to the combined action of the cerium and organophosphate moieties of this inhibitor, in addition to the protective role of yttrium species derived from the yttrium present in the WE43 magnesium alloy.

Scanning Electrochemical Cell Microscopy Stable Imaging Method With a Backpressure at the Back of Its Nanopipet

Scanning electrochemical cell microscopy (SECCM), is a local electrochemical measurement technique with a confined area of a surface, especially suited for the electrochemical mapping with topography imaging in a high-resolution way. Despite its wide application, the droplet evaporation/crystallization of its nanopipet tip impacts imaging stability for the large surface feature. Here we use single-barrel SECCM nanopipet with different backpressure to increase the meniscus droplet thickness and then improve the tip perceptive capability and imaging stability, avoiding the humidity effect. In this paper, finite element method and experiment are first employed to study the impact of the droplet height, contact radius, and half-cone angle of the nanopipet tip on the steady-state current when the meniscus droplet makes contact with the substrate surface. Further, the droplet positioning and SECCM scanning experiments are conducted to compare the imaging stability of the conventional and pressure-applied single-barrel nanopipet with the tip opening diameter 120 nm in different humidity environment. The experimental results demonstrate that the pressure-applied SECCM nanopipet can sense and image with hopping mode in lower ambient humidity and possess higher imaging stability (increase by more than 40% in number of successful images) than conventional nanopipet without pressure.

Communication—A New Approach for SVET Analysis Combined with In Situ Scratching

A novel experimental approach is proposed for creating surface microdefects in situ during SVET analysis. Hot-dip galvanized steel samples fixed in the SVET cell and exposed to 0.05 M NaCl were scratched using a Berkovich indenter. The progress of corrosion activity at defect locations was continuously inferred by SVET scan lines starting 10 s after scribing. The time-dependent inhibitive effect of molybdate was appraised upon repetitive surface damage. The results highlight the interest of combining localized electrochemical techniques with in situ scratching for an improved understanding of time-sensitive corrosion/inhibition processes related to active microscopic defects.