Local Galvanic Cells Research Articles

Effect of external wall defect growth on internal wall corrosion of oil pipelines under mechano‐electrochemical interaction

AbstractThe corrosion mechanism of X80 steel in simulated solutions of acid red soil and product oil sediment under mechano‐electrochemical interaction (MEI) was researched to build a new finite element model through multi‐physical field coupling simulation technology. Based on the new model, the effect of external wall defect growth on the internal wall corrosion of oil pipelines was analyzed in detail. The results showed that the distributions of stress and corrosion of the internal wall were extremely affected by the external wall defect depth, and the corrosion rate of the internal wall was enlarged remarkably by the external wall defect growth. Moreover, attributing to the local galvanic cell effect under MEI, the growth rates of corrosion defects in the depth and length directions of the external defect were accelerated because these directions were associated with larger stress and equivalent to the anode, but the corrosion rate in the width direction of the external defect was inhibited because this direction was associated with smaller stress and equivalent to the cathode.

Microstructure, corrosion behavior, and biocompatibility of Ti-6Al-4 V alloy fabricated by LPBF and EBM techniques

This study aims to investigate the microstructure and electrochemical behavior of the laser powder bed fusion (LPBF-) and electron beam melting (EBM-) manufactured Ti-6Al-4 V alloy in the Ringer′s solution. The microstructure of the LPBF-fabricated part contained the acicular α’ martensite phase, while the EBM-fabricated part possessed a combination of α and β phases. The formation of two phases in the EBM sample can be related to the lower thermal tension and higher temperature of the table during the fabrication process. Electrochemical studies have revealed that the better corrosion performance of the LPBF-manufactured alloy was mainly due to the formation of local galvanic cells in the EBM-manufactured Ti-6Al-4 V alloy. Corrosion current densities of the LPBF- and EBM-manufactured alloys after 100 h of immersion were 0.36 and 0.87 µA cm−2, respectively. MTT assay was performed using MG-63 cells to assess the biocompatibility of the manufactured samples. The results showed that the cells had good adhesion and durability on the samples. Though, both samples could be regarded as good candidates for implant applications, but the LPBF-manufactured part showed a higher resistance corrosion and is then more suitable for implant alloys.

(Invited) Porous Structure Produced By Metal-Assisted Etching of Silicon

Metal-assisted etching of silicon can produce porous silicon and silicon nanowires by simply immersing metal-modified silicon in a hydrofluoric acid solution without electrical bias [1]. Such etching proceeds by a local galvanic cell mechanism consisting of local anodic dissolution of silicon and local cathodic reduction of an oxidizing agent, such as oxygen [2, 3] or hydrogen peroxide, on catalytic metal. The structure of porous silicon is widely controlled from nanometer to sub-millimeter scale in pore size and from straight to an ants’ nest like in pore morphology by changing etching conditions [1-3]. We fabricate various porous structures on silicon wafers, and apply them to antireflection of solar cells and autocatalytic electroless formation of metal-nanorods and metal films on silicon surfaces. The structure of porous silicon is easily controlled in the nanometer scale with changing etching conditions such as kind, size, and distribution of metal catalysts, kind and concentration of oxidizing agent, intensity of photoillumination, and etching time. Recently, we found that general corrosion occurred on the top surface of the silicon substrate around the metal particles even under the dark condition [4]. The general corrosion depended on the metal species and it was explained by the formation and dissolution of a mesoporous layer.[1] Z. Huang, N. Geyer, P. Werner, and U. Gösele, Adv. Mater., 23, 285 (2011).[2] S. Yae, Y. Kawamoto, H. Tanaka, N. Fukumuro, and H. Matsuda, Electrochem. Comm., 5, 632 (2003).[3] S. Yae, M. Tashiro, M. Abe, N. Fukumuro, H. Matsuda, J. Electrochem. Soc., 157, D90 (2010).[4] A. Matsumoto, H. Son, M. Eguchi, K. Iwamoto, Y. Shimada, K. Furukawa, and S. Yae, RSC Adv., 10, 253 (2020).

Influence of Ageing on the Intergranular Corrosion of an Al–Mg–Si Alloy

This report investigates the influence of ageing on the susceptibility to intergranular corrosion (IGC) of an Al–Mg–Si alloy. The selected AA6063 Al-alloy has been exposed to ageing treatments at a predetermine temperature of 423 K for durations of 1 to 168 h to achieve the wide range of ageing states covering under- to peak- to over-aged. The ageing behaviour of the selected alloy has been determined based on the results of hardness and tensile properties. The susceptibility to IGC has been evaluated following the British standard (BS ISO-11846) method B and assessed based on the average and maximum corrosion depths apart from in-depth surface and sub-surface characterizations of corroded specimens. It has been observed that the depths of corrosion increase monotonically with increase in ageing time. With progress of artificial ageing, the dominant mode of corrosion gradually changes in the order of minor pitting, moderate pitting, pitting plus localized IGC, localized IGC and uniform IGC. The phenomenon of preferential dissolution of Mg from the β″ (Mg5Si6) and β (Mg2Si) precipitates as well as the existence of Fe-rich intermetallic particles at the grain boundaries cause the pitting and intergranular corrosion because of the formation of local galvanic cells between the lower corrosion potential of Mg-depleted precipitates or precipitate free zones and to the adjacent anodic grain boundary precipitates.

A self-driven approach for local ion intercalation in vdW crystals.

Intercalation has proven to be a powerful strategy for physical and chemical property modulation in two dimensional (2D) van der Waals (vdW) materials. Traditional gaseous and chemical intercalation methods offer the ability for mass production, and the electrochemical method provides reversible fine tuning for in situ material investigation. Spatial control, or even direct patterning, of ions is widely required for practical device fabrication and integration; yet it is not realized. Here we demonstrate a self-driven ion (Co2+, Sn4+, and Cu2+) intercalation approach with patterning ability on vdW α-MoO3. It is proved that the self-driven intercalation was enabled by the formation of a local galvanic cell and could be controlled by the metal electrode potential and the solution concentration. The universality of self-intercalation was confirmed in various types of 2D materials (MoS2, WS2, MoSe2, WSe2 and graphene). Furthermore, the feasibility of building heterostructures by multiple species (Sn & Co) intercalation in a single nanosheet was demonstrated for broadband photodetection. The enhancement of conductivity and photoresponse was found to be due to the synergistic effect of lattice distortion from Sn intercalation and the d orbital from the Co atom. This approach offers a feasible way for direct nano-fabrication in 2D vdW material and functional device integration.

Excellent long-term reactivity of inhomogeneous nanoscale Fe-based metallic glass in wastewater purification

Metallic glasses (MGs) have attracted great attention in wastewater treatment because of their high reactivity arising from amorphous structure, large residual stress and high density of low coordination sites. However, the reactivity of MGs would gradually slow down with time due to the passivation of active sites by corrosion products, resulting in limited long-term reactivity, which is also an unsolved key issue for established crystalline zero valent iron (ZVI) technology. Here, such problems are successfully overcome by introducing nanoscale chemical inhomogeneities in Fe-based MG (Fe-MGI), which apparently contributes to local galvanic cell effect and accelerates electron transfer during degradation process. More importantly, the selective depletion of Fe0 causes local volume shrinkage and crack formation, leading to self-peeling of precipitated corrosion products and reacted regions. Thereby fresh low coordination sites could be continuously provided, counteracting the mass transport and reactivity deteriorating problem. Consequently, Fe-MGI demonstrates excellent long-term reactivity and self-refreshing properties even in neutral solution. The present results provide not only a new candidate but also a new route of designing ZVI materials for wastewater treatment.

Oxide MnCr2O4 induced pitting corrosion in high entropy alloy CrMnFeCoNi

Composition and structure of the oxide and its effect on corrosion property in the high entropy alloy CrMnFeCoNi have not been revealed so far. In the present work, oxide in CrMnFeCoNi is identified as MnCr2O4 using transmission electron microscopy. Moreover, the oxide MnCr2O4 is detrimental to pitting resistance indicated by comparison study of CrMnFeCoNi with and without the oxide. This is because that the pitting prefers originating from MnCr2O4/matrix interface, in other words, the matrix around oxides dissolves more easily. From the viewpoint of corrosion, MnCr2O4/matrix forms a local galvanic cell, and the matrix as an anode dissolves quickly.

Fabrication of gallium nitride nanowires by metal-assisted photochemical etching

Gallium nitride (GaN) nanowires (NWs) were fabricated by metal-assisted photochemical etching (MaPEtch). Gold nanoparticles (AuNPs) as metal catalyst were electrodeposited on the GaN substrate. SEM and HRTEM images show the surface of GaN NWs is smooth and clean without any impurity. SAED and FFT patterns demonstrate GaN NWs have single crystal structure, and the crystallographic orientation of GaN NWs is (0002) face. On the basis of the assumption of localized galvanic cells, combined with the energy levels and electrochemical potentials of reactants in this etching system, the generation, transfer and consumption of electron-hole pairs reveal the whole MaPEtch reaction process. Such easily fabricated GaN NWs have great potential for the assembly of GaN-based single-nanowire nanodevices.

Metal-assisted photochemical etching of gallium nitride using electrodeposited noble metal nanoparticles as catalysts

Porous gallium nitride (PGaN) layers were fabricated by metal-assisted photochemical etching (MaPCE) using electrodeposited platinum nanoparticles (PtNPs) or gold nanoparticles (AuNPs) as catalysts. After identification of a suitable negative potential and appropriate cyclic voltammetry (CV) conditions, high-density PtNPs or AuNPs were deposited onto a planar GaN substrate. Based on the concrete numerical values of energy levels, the generation, transfer and consumption of electrons and holes, and the assumption that localized galvanic cells are formed, an etching mechanism was proposed which may provide theoretical guidance for future work on etching of GaN and other semiconductor materials.

Effect of welding flash on the corrosion of friction stir spot welded AZ31B

The influence of welding flash on the corrosion resistance of friction stir spot welded (FSSW) AZ31B was examined by mass loss testing complimented with the scanning reference electrode and microcapillary polarization techniques. The microstructure of the flash was characterized by optical microscopy and the use of tungsten carbide tracer and correlated with the corrosion morphology of the joints. It was observed that the flash increased the corrosion rate of the welds, and its removal can reduce the corrosion rate by 20%. The increase in susceptibility for corrosion was explained by examining the electrochemical characteristics of the flash, and in particular to show the presence of a second stir zone (SZ) region in the flash. The electrochemical properties of the flash were correlated to second phase particle dissolution using a detailed microscopy analysis. The coupling of the two regions resulted in the formation of a local galvanic cell in the flash, leading to accelerated corrosion. Increases in dwell time and/or rotational speed of the tool during FSSW resulted in the formation of a larger SZ region in the flash, and produced a greater cathode to anode ratio.

(Invited) Thin Porous Silicon Produced By Metal-Assisted Etching

Metal-assisted etching of silicon can produce porous silicon and silicon nanowires by simply immersing metal-modified silicon in a hydrofluoric acid solution without electrical bias (1). Such etching proceeds by a local galvanic cell mechanism consisting of local anodic dissolution of silicon and local cathodic reduction of an oxidizing agent on metal. The structure of porous silicon is widely controlled from nm to sub-mm scale in pore size and from straight to an ants’ nest like in pore morphology by changing etching conditions (1-3). We have been studying the metal-assisted etching of silicon to produce porous structures for antireflection of solar cells (2), and for autocatalytic electroless formation of metal-nanorods and metal films on Si surfaces (4). In this paper, we present size-controlled thin porous silicon layers consisting of straight pores and those applications. Noble metal nanoparticles were deposited on crystalline silicon wafers by electroless displacement deposition immersing the wafers into a metal salt solution containing hydrofluoric acid. The metal-particle-deposited silicon wafers were immersed in a hydrofluoric acid solution including hydrogen peroxide as an oxidizing agent. Under suitable etching conditions, uniform porous silicon thin layers consisting of straight pores were formed on silicon wafers. The diameter of pores was consistent with the size of metal nanoparticles remained at the bottom of each pore. Thus, the diameter of pores, that is, the porosity of porous layers is easily controlled in the nm scale with the deposition time of nanoparticles. The thickness of porous layers, that is, the length of the straight pores is also easily controlled by the etching time. Optical properties of the porous layers thinner than 1 μm depends on those porosity and thickness (5). This is applicable for antireflection of solar cells. The strength of metal nanorods, which were produced by electrolessly filling the pores, increased with the diameter of pores from 10 to 25 nm. These nanorods work as nanoanchors of metal films on silicon wafers. Acknowledgements The present work was partly supported by JSPS KAKENHI (26289276). References 1) Z. Huang, N. Geyer, P. Werner, J. de Boor, U. Gösele, Adv. Mater., 23, 285 (2011). 2) S. Yae, H. Tanaka, T. Kobayashi, N. Fukumuro, H. Matsuda, Phys. Stat. Sol. (c), 2(9), 3476 (2005). 3) S. Yae, M. Tashiro, M. Abe, N. Fukumuro, H. Matsuda, J. Electrochem. Soc., 157, D90 (2010). 4) S. Yae, K. Sakabe, N. Fukumuro, S. Sakamoto, and H. Matsuda, J. Electrochem. Soc., 158, D573 (2011). 5) K. Yamakawa, S. Sakamoto, N. Fukumuro, S. Yae, ECS Trans., 69(2), 185 (2015).

Evaluation of the effect of ageing heat treatment on corrosion resistance of Al–Ag alloy using electrochemical methods

Abstract

Metal-Assisted Etching of Silicon: Activity of Metal Catalysts and Control of Porous Structure

Metal-assisted etching of silicon has attracted considerable attention as an electroless method that can produce porous silicon and silicon nanowires by simply immersing metal-modified silicon in a hydrofluoric acid solution without electrical bias (1). Such etching generally uses not only metal-modified silicon wafer but also an oxidizing agent. The common oxidizing agent is hydrogen peroxide. We have been using dissolved oxygen in hydrofluoric acid solution as the oxidizing agent, which promotes much slower etching than that using hydrogen peroxide (2, 3). The metal-assisted etching proceeds by a local galvanic cell mechanism consisting of local anodic dissolution of silicon and local cathodic reduction of the oxidizing agent on metal. We have been studying the metal-assisted etching of silicon to produce porous structures for antireflection of solar cells for photovoltaics and photoelectrochemical solar hydrogen production (2-4), and for autocatalytic electroless formation of metal-nanorods and adhesive metal films on Si surfaces (5). In this paper, we present various porous structures produced by the metal-assisted etching using several kinds of noble metals (6-8), and discuss control factors and formation mechanisms of the structures. Noble metal nanoparticles were deposited on crystalline silicon wafers by electroless displacement deposition immersing the wafers into a metal salt solution containing hydrofluoric acid (9). The size and particle density of deposited metal particles were controlled by deposition conditions such as the concentration of metal salts and deposition time. The metal-particle-deposited silicon wafers were immersed in a hydrofluoric acid solution including oxygen or hydrogen peroxide as an oxidizing agent. Figure 1 shows porous structures having variety of pore-size between nanometers and sub-millimeters. Photoillumination during etching generates electron-hole pairs in silicon, and thus enhances and de-localizes the etching reaction (Fig. 1c). Metals on silicon catalyze the local cathodic reaction thus their kind, size, and particle density change the etching rate. Palladium and ruthenium have high catalytic activity for the etching of silicon (6, 8). Under suitable conditions, the anodic dissolution of silicon is localized under the metals (Fig. 1b and d). Oxidizing agents promote the local cathodic reaction thus their kind and concentration change the etching rate and nanopore shape. Electrolessly deposited silver nanoparticles and hydrogen peroxide produce a uniform thin porous layer, which works as an optical antireflection film for solar cells, consisting of straight nanopores having metal nanoparticle on each bottom (4). ACKNOWLEDGEMENTS The present work was partly supported by JSPS KAKENHI (26289276). REFERENCES (1) Z. Huang, N. Geyer, P. Werner, J. de Boor, U. Gösele, Adv. Mater., 23, 285 (2011). (2) S. Yae, Y. Kawamoto, H. Tanaka, N. Fukumuro, and H. Matsuda, Electrochem. Comm., 5, 632 (2003). (3) S. Yae, in Solar Cells - New Aspects and Solutions, Ch. 11, p. 231 (InTech, 2011). (4) K. Yamakawa, S. Sakamoto, N. Fukumuro, and S. Yae, This symposium(2015). (5) S. Yae, K. Sakabe, N. Fukumuro, S. Sakamoto, and H. Matsuda, J. Electrochem. Soc., 158, D573 (2011). (6) S. Yae, M. Tashiro, M. Abe, N. Fukumuro, and H. Matsuda, J. Electrochem. Soc., 157, D90 (2010). (7) S. Yae, Y. Morii, N. Fukumuro, H. Matsuda, Nanoscale Res. Lett., 7, 352 (2012). (8) D. Sadakane, K. Yamakawa, N. Fukumuro, and S. Yae, This symposium(2015). (9) S. Yae, N. Nasu, K. Matsumoto, T. Hagihara, N. Fukumuro, and H. Matsuda, Electrochim. Acta, 53, 35 (2007). Figure 1

Enhanced degradation of azo dye by nanoporous-copper-decorated Mg–Cu–Y metallic glass powder through dealloying pretreatment

Abstract A controllable uniform nanoporous copper (NPC) layer was synthesized on the surface of the ball-milled powder of Mg65Cu25Y10 metallic glass by dealloying. The morphology, the elemental surface composition and the phase structure of the powders were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry, respectively. The composite powder with a core–shell structure shows higher degradation efficiency of the azo dye of Direct Blue 6 than the untreated powder and the pure NPC. The improved performance can be attributed to the strong synergistic effect between the NPC layer and the metallic glass matrix, because the nanoporous structure provides large surface area for the adsorption of the dye molecules and three-dimensional diffusion channels of reaction masses, as well as the dissolution acceleration of the active atoms through local galvanic cell reaction. This tunable pretreatment is a promising surface activation method for novel chemical applications of metallic glasses.

Effect of microstructures on corrosion and erosion of an alloy steel gear pump

Investigation on an alloy steel gear-pump has been carried out to understand the effect of microstructures on corrosion and erosion behavior of the material. The alloy tool steel gear pump was designed to replace an existing pump made of grey cast iron to increase the service life to 7–8years from 4–5years. However, the new pump, used for dispensing hot adhesive polymer at 170°C and 8bar pressure, was damaged due to pitting corrosion within one year of service. Local galvanic cells were formed between M23C6 carbides and martensite matrix of steel plate of the pump in presence of sulfide ions sourced from liquid adhesive followed by anodic dissolution of martensitic matrix surrounding the carbides. As a consequence, hard carbide particles were dislodged and facilitated the pump to undergo wear rapidly.

Corrosion of aluminum electrodes in aqueous slurries for lithium-ion batteries

Current manufacturing methods for lithium ion batteries use a non-aqueous solvent for producing slurries of cathode active materials and applying them to the aluminum current collectors. Transition to a water-based process may be desirable to reduce volatile organic compound emissions and costs, and increase processing efficiency. This transition may lead to additional complexities such as corrosion that could impact the performance of cells in service. The current work shows that the use of aqueous-based slurries for manufacturing lithium ion batteries can lead to general and pitting corrosion of the aluminum alloy foils used as current collectors with contact times as short as 100 s. Pitting corrosion initiates due to localized galvanic cells between cathodic intermetallic particles present in the aluminum alloy and the locally anodic aluminum matrix. The extent of pitting and amount of general corrosion product formed differs when using slurries of different active material compositions and increases with slurries of higher inherent pH. The presence of the intermetallic particles in the aluminum alloy is expected based on the chemical composition of the material. While elimination of the intermetallics from the aluminum is possible by increasing the purity of the material, it is unlikely that this mitigation strategy would be implemented due to economic considerations.

Reduction of heat generation for lithiated graphite by forming a local galvanic cell with Cu3Sn at elevated temperature

A copper–tin intermetallic compound (Cu3Sn) is deposited on copper foil and used as the current collector for graphite electrode. The Cu3Sn phase is inactive for lithiation at ambient temperature, but becomes active to be lithiated at elevated temperatures. Hence, when the Cu3Sn deposit, which makes an intimate contact with the lithiated graphite, is exposed to high-temperature environment, it is lithiated by taking Li+ ions/electrons from the lithiated graphite. As a result, the degree of lithiation in graphite decreases. The formation of local galvanic cell, in which Li+ ions/electrons are transferred from the graphite electrode to the Cu3Sn deposit, is confirmed by electrochemical and X-ray diffraction analysis. The heat generation that is resulted from the exothermic reactions between graphite and electrolyte, which is known to be smaller with a decrease in the degree of lithiation in graphite, is greatly reduced as a result of galvanic cell formation. In short, Cu3Sn can be added into graphite electrodes to enhance thermal safety of lithium-ion batteries.

Development of a finite element model for simulation and prediction of mechanoelectrochemical effect of pipeline corrosion

In this work, a finite element model was developed to study mechanoelectrochemical effect of pipeline corrosion through a multiphysics field coupling technique. The modeling results, i.e., corrosion potential and corrosion current density, are well consistent with experimental measurements on pipeline steel in a near-neutral pH solution. It is demonstrated that, while a tensile strain enhances stress uniformly through pipe wall, an increasing depth of corrosion defect results in a concentrated stress at the defect center only. When the corrosion defect is under an elastic deformation, there is no apparent effect of mechanical–electrochemical interaction on corrosion. However, when the applied tensile strain or the geometry of corrosion defect is sufficient to cause a plastic deformation at the defect, the local corrosion activity is increased remarkably. Corrosion at the defect is composed of a series of local galvanic cells, where the region with a higher stress, such as the defect bottom, serves as anode, and that under lower stress, such as the defect sides, as cathode. The locally accelerated corrosion at the defect center can be further enhanced as the corrosion defect deepens.

Characterization of corrosion phenomena of Zr–Ti–Cu–Al–Ni metallic glass by SEM and TEM

Corrosion phenomena are investigated for a Zr 59Ti 3Cu 20Al 10Ni 8 metallic glass immersed in hydrofluoric acid (HF) in open-circuit conditions and by means of electron microscopies (SEM and TEM). Several morphologies develop on the corroded surface and especially large and deep pits. TEM study demonstrates that Cu-rich nanocrystals of 5–10 nm are formed inside the corrosion pits (on their walls) during the corrosion process. These nanocrystals are not only by-products of the corrosion process but they very likely play a role in the development of the corrosion pitting morphology. They could have a dual role: (i) protecting the capped areas against dissolution and (ii) speeding the dissolution of neighboring uncapped areas by the creation of local galvanic cells.

Electrochemical response of amorphous and devitrified Al‐Ni‐La‐X (X = Ag, Cu) alloys

AbstractThe electrochemical response of melt‐spun Al‐Ni‐La alloys with partial substitution of Ni after different stages of devitrification was studied. The base alloy was found to have the best corrosion resistance. It was observed that primary crystallization caused minimal deterioration in the corrosion resistance of the base alloy as compared to its amorphous state. The substitute alloys had different corrosion resistance dependent on the substituting element with the Ag containing alloy having the least resistance. This could be attributed to the operation of local galvanic cells, enhanced by chemical heterogeneities in the alloys. Secondary crystallization caused a reduction in the corrosion resistance of all the alloys due to the creation of intermetallic phases that increased the galvanic activity.