bluuebunny/crossref_metadata_2025 huggingface dataset:
Failure Analysis of Boiler Water Wall Tube for Power Generation in District Heating
Authors: Lee Soo Yeol , Hong Minki , Chae Hobyung , Kim Woo Cheol , Kim Jung Gu , Kim Heesan
Published: February 2020

A corrosion failure of materials, often exposed to the corrosive environment in the district heating facility, has a critical influence on structural integrity. Thus, it is very important to investigate the cause of the failure for the establishment of effective prevention methodology. In this study, the failure analysis was performed in the case that a water wall tube for a boiler in district heating was fractured along the axial direction of the tube that is SA-210 Grade A1, which is frequently used for the boiler. The feed water temperature was about 220°C and the operating pressure was about 10 MPa. For the visual inspection of the failed part, the wall thinning and failure were observed in the location where the heat was directly reached. Sodium and iron oxides were only found in the inner surface of the tube, as confirmed by x-ray diffraction, and it indicates that hydrogen is generated by the mechanism of the caustic corrosion, resulting in hydrogen embrittlement near the inner surface. The microstructural changes along the direction of radial and hoop were intensively examined. A number of microvoids were formed along the grain boundary, leading to some microcracks in the location inside the tube. As a result, it is concluded that an unstable magnetite film at elevated temperature under tensile residual stresses developed along the hoop direction in the interior of the tube undergoes the caustic corrosion, and microvoids or microcracks along the grain boundary formed due to hydrogen embrittlement cause a final fracture of the tube.
Understanding the Scales Formation Inhibition Mechanism on C-Steel in a Sour media
Authors: Al-Qahtani Noora , Qi Jiahui , Abdullah Aboubakr Moustafa , Laycock Nick , Ryan Mary P
Published: February 2020

Corrosion control in sour environments is a serious challenge for oil and gas industry. One of the approaches to mitigate such problem is to use corrosion inhibitors (CI). The selection of a single or a mixture of CIs for a particular oil or gas production, transportation or storage facility depends on different parameters e.g. the ratio between carbon dioxide and hydrogen sulfide, pH, pressure, temperature, and brine chemistry where different kinds of iron sulfide and/or iron carbonate layers can be formed. To select the right corrosion inhibitor/s, it is highly crucial to understand the mechanism of corrosion of C-steel and its inhibition in H2S systems in absence and presence of CIs [1,2].

In this work, the electrochemical behavior of C-steel in (i) deionized water (DIW) and (ii) different NaCl solutions were examined in an H2S system. A series of experiments were conducted at different temperatures and two concentrations of inhibitors (A and B). The corrosion behavior of C-steel was investigated by measuring the open circuit potential (OCP), linear polarization resistance (LPR), and potentiodynamic polarization (PDP) in addition to scanning electron microscopy (SEM) coupled with an energy dispersive X-ray (EDX) besides Raman spectroscopy (RS). The results have shown that the corrosion rate of C-steel gradually decreased then stabilized with time in the inhibited solutions. The inhibition efficiency was found to increase in the presence of both types of inhibitors with temperatures. Surface analysis shows that no film of corrosion products existed. In fact, CIs controlled the corrosion process and prevented passive film formation (iron sulfide), even in the presence of H2S in all tests. 2.5.0.0 2.5.0.0
The Underoil Droplet Corrosion Behavior of X100 Pipeline Steel
Authors: Liang Hongxing , Liu Jing , Schaller Rebecca Filardo , Asselin Edouard
Published: February 2020

Canadian natural bitumen production will reach a peak of 112 million barrels per day in 2078 [1]. Pipelines are primarily used to transport this bitumen. Bitumen must be diluted in order to be pumped through a pipeline effectively because it is otherwise too viscous to flow [2]. Underoil droplet corrosion of diluted bitumen (dilbit) pipelines may lead to the loss of pipe wall thickness, which deteriorates the structural reliability and increases the risk of leaking of pipelines. The current models for atmospheric droplet corrosion, where no limitation to oxygen access is imposed, cannot be applied to underoil droplet corrosion in dilbit pipeline conditions.

In this study, a NaCl droplet on X100 pipeline steel covered by paraffin oil is used to simulate the corrosive environment encountered in diluted bitumen pipelines. A new distinctive corrosion mechanism is proposed to explain the corrosion of X100 pipeline steel beneath an underoil salty droplet. This mechanism accounts for the depleted oxygen levels in the droplet environment. In the initial stage (1 h), the distribution of corrosion pits was heterogeneous with one area under the droplet presenting a higher pit density. As the corrosion proceeded (24 h), the localized corrosion was governed by pH development due to initial pit density. Regions of initially higher pit density switched to general corrosion, while regions with lower pit densities continued pitting.

The effects of droplet volume, chloride ion concentration, and temperature on the underoil droplet corrosion behavior of X100 pipeline steel were also studied by scanning electron microscopy, Raman spectroscopy, and profilometry. At 23 °C, lepidocrocite and hematite were observed in the region where pitting was initially prevalent. However, as this region switched to uniform corrosion, goethite, lepidocrocite, and hematite were formed. The same distribution of crystal structures was identified for the droplets with varying volume and chloride ion concentration. When the temperature was increased to 60 °C, hematite was detected in both regions. Decreased droplet volumes, increased chloride concentration, and raised temperatures increase corrosion penetration when uniform corrosion is prevalent. This study provides important findings to better understand the mechanisms behind droplet corrosion underoil and informs future predictions of the corrosion rate of pipeline steels.

References

[1] S. H. Mohr and G. M. Evans. Long term prediction of unconventional oil production. Energy Policy 2010; 38: 265−276.

[2] National Research Council of the National Academy of Sciences, Effects of diluted bitumen on crude oil transmission pipelines, in: Transportation

Research Board Special Report 311, Washington DC, 2013.
EIS Study on Effects of Inorganic Inhibitors on Localized Corrosion on Stainless Steels at PEFC Environments
Authors: Ueyama Meiko , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki , Takata Satoshi , Kogure Tomonari
Published: February 2020

Stainless steel is considered as a suitable material of PEFC metal separator because it has good durability, formability, chemical stability and reasonable price. Whereas, localized corrosion would occur on stainless steel due to potential and temperature change during PEFC operation because a metal separator contacts with acidic solution containing fluoride and chloride ions. It is generally known that a few percent of molybdenum as an alloy element inhibits localized corrosion. Hashimoto et. al.
1) proposed that dissolved molybdenum from stainless steel affected protection of steel surface. In previous study2), we discussed anti-corrosive effects of molybdate ions as an inhibitor in solution. In present study, we investigate inhibitor mechanisms of sodium molybdate, sodium tungstate and sodium phosphate for localized corrosion of stainless steel by electrochemical impedance spectroscopy.

In this study, measurement of polarization curve and electrochemical impedance were conducted by three electrode methods. The working electrode was S44700 (Surface area : 0.28 cm2). The counter electrode was platinum wire and the reference electrode was a saturated KCl/Ag/AgCl (SSE) electrode. The electrolyte solution simulating PEFC operation environment (PEFC simulating solution) was 1 mol/dm3 H2SO4 aqueous solution (pH 3) which contained 10 ppm NaCl and 30 ppm NaF. Furthermore, some inorganic inhibitors were added to PEFC simulating solution as follows: 1 mmol/dm3 sodium molybdate, sodium tungstate or sodium phosphate. Polarization curves were measured by scanning the working electrode potential at 100 mV min-1 from open circuit potential to 1.5 V vs. SSE. Impedance measurements were carried out at potentials in passive and transpassive regions. Imposed AC potential amplitude was 10 mV and frequency ranges were from 10 mHz to 10 kHz.

Figure 1 presents polarization curve and impedance spectra of S44700 in PEFC simulating solution. The polarization curve is composed of passive region from open circuit potential to 0.8 V vs. SSE and transpassive region from 0.8 V to 1.5 V vs. SSE. Impedance spectra show blocking behavior at passive region (0.7 V, 0.8 V vs. SSE) and inductive loops at transpassive regions (0.9 V, 1.0 V vs. SSE). In present study, we investigate inorganic inhibitors reducing transpassive dissolution current. Then, we propose inhibitor mechanisms of sodium molybdate, sodium tungstate and sodium phosphate by EIS.

References

1) K. Hashimoto, K. Asami, M. Naka and T. Masumoto, Corros. Sci., 19, 857 (1979).

2) M. Ueyama, C. Tsukioka, Y. Hoshi, I. Shitanda, M. Itagaki, S. Takata, and T. Kogure, C01 – 697, 232 nd ECS Meeting.

Figure 1
Corrosion Behavior of AISI 316 Stainless Steel As Reinforcement in Ternary Sustainable Concrete Based on Scba-SF Exposed in Seawater
Authors: Landa-Gómez Aldo , Croche B René , Lopez Yza Oscar Manuel , Galván-Martínez Ricardo , Cabral-Miramontes Jose A. , Tiburcio Citlalli Gaona , Almeraya Facundo , Baltazar-Zamora Miguel Angel
Published: February 2020

In the present research the corrosion behavior of AISI 316 Stainless Steel was analyzed, as reinforcement in Ternary Concretes made with partial substitutions of the Composite Portland Cement (CPC) by combinations of Sugar Cane Bagasse Ash (SCBA) and Silica Fume (SF) in different percentages, compared to AISI 1018 steel. Four concrete mixtures were made, all with a ratio w / c = 0.65, the percentages of substitution were 0%, 10%, 20% and 30%. The specimens were exposed in seawater as an aggressive medium, corrosion was evaluated by monitoring the corrosion potential Ecorr (ASTM C-876-15) and corrosion rate Icorr (ASTM G59). The results of Ecorr and Icorr after 150 days of exposure show a better performance of AISI 316 steel, with a 10% of probability corrosion and a negligible level of corrosion respectively, the Ternary Concrete with 20% partial replacement of the CPC by the combination of SCBA-SF presented the best protection against corrosion.
Influence of Carbon Dioxide on the Atmospheric Corrosion of Zinc-Aluminium and Zinc-Aluminium-Magnesium Coated Steel
Authors: le Bozec Nathalie , Thierry Dominique , Le Gac Anne , Persson Dan
Published: February 2020

The superior corrosion resistance of hot dip galvanized steel (HDG) alloyed with addition of Al and Mg compared to conventional zinc coating has been shown in numerous atmospheric conditions including accelerated tests and natural exposures. Despite significant work in understanding the mechanisms of corrosion of Zn-Al-Mg coatings, there are still gaps of knowledge such as, on the exact interactions between the complex microstructure of theses coatings and their corrosion properties. A large European (RFCS) project namely MicroCorr has been initiated in 2015 with the aims of better understanding these aspects. On task was to examine the effect of surface pH and contaminations as well as relative humidity and temperature on the corrosion performance of well-defined microstructures of alloyed zinc coatings with Al and Mg.

The present study focuses on the effect of carbon dioxide depletion on the atmospheric corrosion stability of Zn alloyed coatings compared to conventional HDG (Zn-0.2Al) and Galfan (Zn-5Al). Zn-Al-Mg and Zn-55Al coatings produced with various microstructures differing in the grain size were investigated in low and ambient concentration of CO2 with two levels of chloride concentration. In addition to mass loss data, the surface pH was measured using wide range pH indicator in agar-agar gel. The corrosion products were analyzed by FTIR spectroscopy and X-Ray diffraction.

The corrosion of HDG and zinc alloyed coatings with low content of Al and Mg was significantly enhanced in low CO2 conditions particularly at high chloride concentration and whatever the microstructure. This was connected to a high surface pH in the absence of CO2. Surprisingly, similar weight losses were measured for Zn-55Al coatings whatever the level of CO2 and no increase of surface pH was observed even in depleted CO2 conditions. However, important localised corrosion was observed for this coating
Hydrophobic Porous Layer By Plasma Electrolytic Oxidation of Magnesium Alloy for Corrosion Resistance
Authors: Joo Jaehoon , Jung Haechang , Lee Junghoon
Published: February 2020

Magnesium and its alloys have aroused significant attention in a wide range of applications, due to their superior dimension stability, thermal conductivity, damping capacity and high specific strength. Nevertheless, the corrosion resistance is a critical issue in the practical application of the magnesium and its alloys, thus various strategies have been introduced to prevent or impede the corrosion of magnesium. Especially, a plasma electrolytic oxidation (PEO), which forms a thick oxide layer, is considered as a promising technology to passivate the magnesium and its alloys. However, the PEO treated surface shows a great wettability to water and corrosive liquid, the corrosion resistance is not sufficient for the practical applications. In this work, we employed a self-assembled monolayer coating on PEO treated surface of magnesium alloy to hydrophobize the porous oxide layer. The hydrophobic coating enabled the porous oxide layer by PEO to retain air within irregular pores, so that the penetration of corrosive liquid toward the magnesium alloy substrate is prevented. Therefore, the hydrophobized porous oxide layer significantly improved the corrosion resistance of magnesium alloy compared to the hydrophilic porous oxide layer absorbing the corrosive liquid easily. Moreover, due to the porous and rough nature of PEO layer, the hydrophobized surface shows a high mobility of water, thus the self-cleaning property can be realized on the surface of magnesium alloy.
Corrosion Behavior of Multilayer PVD Coatings on Inconel Alloy 718
Authors: Almeraya Facundo , Tiburcio Citlalli Gaona , Perez Ortiz Dafne , Cabral José Angel , Zambrano Patricia , Montoya Marvin
Published: February 2020

The multilayer PVD coatings are used in the aeronautics industry due to high resistance of pitting and crevice corrosion. In this study, the corrosion behavior of multilayers AlCrN/TiSi (85/15), AlCrN/Ti + CrSi and AlCrN/AlCr (70/30) + Cr coatings deposited by Physical Vapor Deposition (PVD) technique were studied. The first layer was deposited from high purity targets of Al and Cr in an N atmosphere at a temperature of 450 °C on 100x100x5 mm plates of Inconel 718 substrate. The second layer was deposited at different temperatures in an inert atmosphere. The multilayer PVD coatings were evaluated by Scanning Electron Microscope (SEM) and potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) measurements were performed in NaCl and H2SO4 solutions. The SEM results showed an adequate distribution of the coatings on the substrate. For the anodic region of the potentiodynamic polarization curves showed that Inconel 718 alloy and PVD coating exhibited a tendency to pseudopasivation behavior in the different corrosive environments. It is observed that some curves have positive hysteresis could be interpreted as susceptibility to pitting corrosion and the Nyquist diagrams two semicircles corresponding to the coatings and the substrate are observed. In general, multilayer PVD coating have a higher corrosion rate in H2SO4, and both multilayers PVD AlCrN/TiSi (85/15) and AlCrN/AlCr (70/30) + Cr coating present pitting corrosion in NaCl and H2SO4, respectively.
Atmospheric Corrosion Study to Painted Galvanized Steels Under Maritime, Industrial and Urban Conditions
Authors: Almeraya Facundo , Tiburcio Citlalli Gaona , Bernal Ponce Vanessa , Ramirez Reyes Jose Luis , Rodriguez-Gomez Francisco Javier , Barrios Carlos Paulino , Garcia R. Omar , Pedraza Juan Pablo , De la Garza Maribel , Vazquez Rodriguez Carlos
Published: February 2020

The atmospheric corrosion, potentially destructive consuming sources and time, is the electrochemical process in which metals are deteriorate by atmospheric factors, that include the effect of climate conditions (periods of wetting and drying, temperature, humidity, rainfall, wind speed and direction, solar and ultraviolet radiation) and the effect of pollution (SO2, NaCl, CO2, NOx and solid particles). Another factor is that atmospheric corrosion involves chemical, electrochemical and physical process in three mater states (solid, liquid and gaseous) and two interfaces (solid/liquid and liquid/atmosphere).

In the present study painted galvanized steel sheets were exposed to different environments which include marine, industrial and urban conditions. The aim was study the corrosion behavior of the materials in the different climatic environments. To characterize the corrosion behavior a photographic register was done and an analysis of the layers in cross section with a scanning electron microscope.
Electrochemical Evaluation of Natural Compounds As Green Corrosion Inhibitors for Iron
Authors: Roncagliolo Barrera Paola , Rodriguez-Gomez Francisco Javier
Published: February 2020

The protection against corrosion of iron is of utmost importance when it comes to preserving sculptures located in outdoor or indoors environments. The corrosion of iron implies not only an aesthetic deterioration of the original surface, but also an invaluable loss of history. Its restorer common practice; use inhibitors for protection of metals, which are applied directly in the metal and subsequently coated with temporary protection. Much work has been done with synthetic inhibitors, but some of them have high ecological impact and toxic. Research focus to evaluated nicotine and caffeine as green iron corrosion inhibitors for apply in artifact's preservation by electrochemical techniques; Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy(EIS) and Electrochemical Noise (EN). Results showed that the best inhibited effect was nicotine presents a combined adsorption process of chemisorption and physisorption. Both caffeine and nicotine added as corrosion inhibitors showed an improvement corrosion protection
SVET Study of Amines Attack of MnS Inclusions and the Consequences for Pitting and SCC Nucleation
Authors: Dick Luís Frederico Pinheiro , Lopes Natalia Feijó , Martins Tarso , Pritzel dos Santos Alvaro
Published: February 2020

Sulfide inclusions are preferred nucleation sites for the localized corrosion of carbon and stainless steels. Thus, inclusions distribution and composition are important for the occurrence of pitting, crevice and the different forms of stress corrosion cracking. Amines are usually used for the removal of sulfides, with the precipitation of carbamates by the production of environmental friendly fuels with low S contents. On the other hand, amines are also used associated to formation/injection waters simultaneously to CO2 reinjection by the offshore oil production at high pressures, usually under the assumption that it will act as a corrosion inhibitor, as well.

In the present work, we show that amines, usually seen as corrosion inhibitors may enhance the attack to sulfide inclusions in unalloyed carbon steels. For this, artificial galvanic elements with carbon steel (AISI 1006) and MnS tablets (Figure 1.a and 1.c), simulating an inclusion, were studied by SVET (scanning vibration electrode technique) (Figure 1.b and1.d) and other techniques to evaluate the influence of amine (1% tetraethylenepentamine-TEPA) on the corrosion in Na2SO4solutions. Carbon steels (e.g. SAE1006) exposed to dilute sulfate solutions show the typical passive behavior with pitting at higher potentials. The amine “TEPA” shifts the pitting potential to higher values, as expected (Fig. 3a). MnS inclusions show the opposite behavior and its dissolution is promoted when TEPA is added in significant concentrations (Fig. 3b). Accordingly, SVET measurements show that the addition of TEPA can invert the galvanic pair formed by Fe-MnS (Fig. 1). At OCP, a synthetic MnS inclusion is attacked progressively by TEPA as Fig.2 shows for different exposure times. This has significant consequences for the initiation of pitting and stress corrosion cracking of steels, as verified by SVET measurements under simultaneous mechanical strain.

Figure 1
Localized Corrosion of Lean–Duplex Stainless Steel Reinforcements in Alkaline Solution
Authors: Bastidas David M.
Published: February 2020

Understanding of localized corrosion mechanism of lean-duplex stainless in alkaline soltuiion is a key issue on construction and civil engineering industry, because the growing use and application of SS in those sectors. Duplex stainless steel improves the lifetime in service of reinforced concrete structures (RCS), thus combining good corrosion and mechanical properties. This research work studied corrosion behavior of duplex stainless steel rebars RCS: LDSS 2001, AISI 2304 and AISI 2205. Corrosion testing was performed in alkaline media under high chloride content conditions, [Cl–]= 4; 6 and 8%. Results allowed to elucidate chloride threshold on localized pitting corrosion, passive layer chemistry and electrochemical behaviour, for different duplex stainless steels reinforcements. The evolution with time of corrosion potential (E
corr) and polarization resistance (R
p) was studied. Polarization resistance and time constant (τ) were obtained by potentiostatic pulse technique.

Duplex stainless steel reinforcements revealed pitting corrosion after 6 months exposure in high chloride contained alkaline solutions (pH>12). Despite of pitting corrosion, a very low corrosion risk was found for duplex stainless steel used.
Spatially-Resolved Detection of Hydrogen Absorbed into Pure Iron Using Electrochromic Tungsten Oxide Thin Film
Authors: Sugawara Yu , Sakaizawa Yuto , Shibata Akihiro , Muto Izumi , Hara Nobuyoshi
Published: February 2020

The initial stage of hydrogen embrittlement is hydrogen absorption. In atmospheric environments, hydrogen absorption into steel occurs as a result of the cathodic reaction during corrosion process. Because the hydrogen absorption behavior is sensitive to surface heterogeneity, it is an important subject to clarify the distribution of hydrogen absorption on steel surface for reducing the risk of hydrogen embrittlement.

Electrochemical hydrogen permeation cell developed by Devanathan et al.1) is effective in evaluating the hydrogen permeation rate and the diffusion coefficient of hydrogen, but it cannot measure the distribution of hydrogen absorption. A new and easy detection system to obtain the distribution of hydrogen absorbed into steel has been required.

We therefore fabricated a detection system for hydrogen absorbed into steel using WO3. After WO3 thin film was formed in the back side of an iron sheet (hydrogen detection side), hydrogen was absorbed into the iron sheet by the cathodic polarization in the front side (hydrogen entry side). Then, the change in the optical property of the WO3 thin film by hydrogen permeating through the iron sheet was examined.

Pure iron sheets 1 mm in thickness were used for the hydrogen detection test. Prior to the test, the surface of the hydrogen detection side was electrochemically plated with Pd. After the Pd-plating, the WO3 thin film was formed by reactive rf magnetron sputtering. The hydrogen evolution and absorption were performed by the potentiostatic polarization at -0.720 V in a 0.1 M H2SO4 solution. The surface of the WO3 film in the hydrogen detection side was observed by a video camera during the polarization.

The hydrogen detection test with the WO3 thin film shows that the color in the WO3 film gradually changed from a light blue to a dark blue. In addition, the color of the WO3 film around the area corresponding to the electrode region in the hydrogen entry side mainly altered. This result suggests that the optical property of the WO3 thin film in the hydrogen detection side changed by hydrogen absorbed into the iron sheet in the hydrogen entry side. XPS result shows that HxWO3 was formed at the dark blue area in the WO3 film after the hydrogen detection test. Therefore, the formation of HxWO3 by the absorption of hydrogen seems to result in the color change of WO3.

1) M. A. V. Devanathan and Z. Stachurski, Proc
.
Roy
. Soc., A270, 90-102 (1962).
Application of Channel Flow Double Electrode to pH Detection of Magnesium Dissolution during Anodic Polarization
Authors: Hoshi Yoshinao , Miyazawa Kei , Shitanda Isao , Itagaki Masayuki
Published: February 2020

An elucidation of magnesium dissolution mechanisms is one of the key issues for wider usage of magnesium and its alloys in industry because the magnesium has high reactivity in aqueous solutions. The hydrogen evolution rate is increased with positive polarization from the open circuit potential, which is the so called negative difference effect (NDE).1,2 The real-time hydrogen measurement methods have been developed to investigate the NDE.3-6

Authors7 developed a pH sensing channel flow double electrode (CFDE) in order to investigate the pH changes due to the magnesium dissolution. Our group8-10 have been applied the CFDE for analysis of dissolution mechanisms of copper and copper alloys because the oxidation state of the metal ions dissolved from the metal working electrode (WE) can be detected by arranging a detecting electrode (DE) downstream of the WE. In the pH sensing CFDE, the DE was used as the pH sensor, namely, the hydroxide ions generated during the anodic polarization of magnesium WE can be detected at the pH sensor. It indicates that this method allows for the estimation of the hydrogen evolution rate from pH values without the hydrogen gas collection. In addition, a video recording of the WE surface was performed during the measurement in this system.

In the present study, the magnesium dissolution during anodic polarization was examined by the pH sensing CFDE. The relationship between the breakdown of the oxide film formed on the magnesium surface and increase of pH was discussed, and the hydrogen evolution rate was estimated from the pH values.

References

G. Song, A. Atrens, D. St John, X. Wu and J. Nairn, Corros. Sci., 39, 1981 (1997).

G. S. Frankel, A. Samaniego and N. Birbilis, Corros. Sci., 70, 104 (2013).

M. Curioni, Electrochim. Acta, 120, 284 (2014).

S. Lebouil, A. Duboin, F. Monti, P. Tabeling, P. Volovitch and K. Ogle, Electrochim. Acta, 24, 176 (2014).

S. Fajardo and G. S. Frankel, Electrochim. Acta, 165, 255 (2015).

Y. Hoshi, R. Takemiya, I. Shitanda and M. Itagaki, J. Electrochem. Soc., 163, C303 (2016).

Y. Hoshi, K. Miyazawa, I. Shitanda and M. Itagaki, J. Electrochem. Soc., 165, C243 (2018).

M. Itagaki, M. Tagaki, T. Mori and K. Watanabe, Corros. Sci., 38, 601 (1996).

Y. Hoshi, M. Itagaki, K. Tabei and I. Shitanda, J. Solid State Electrochem., 19, 3551 (2015).

Y. Hoshi, T. Oda, I. Shitanda and M. Itagaki, J. Electrochem. Soc., 164, C450 (2017).
Changes in Surface Potential Distribution Due to Hydrogen Permeated through Pure Iron
Authors: Yanai Kasumi , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki , Katayama Hideki
Published: February 2020

Further strengthening of steel materials is required in recent years from the viewpoint of energy saving and resource saving. However, hydrogen embrittlement is well known to be more sensitive to high-strength steel, and especially it is an urgent matter to solve the problem related to hydrogen embrittlement caused by corrosion. A technology for visualization of penetration or permeation hydrogen is required as a method to solve it. Katayama et al. report that distribution of permeated hydrogen can be visualized by surface potential measurement. In addition, they shows that the time during which the surface potential change due to permeated hydrogen is observed varies depending on the environment of the hydrogen detection side. However, it is not clear what the environment dependency of hydrogen observation time is attributed to. In this study, it is focused on the relative humidity as the environmental factor of the hydrogen detection side, and hydrogen permeation behavior was monitored by surface potential measurement under the environment of hydrogen detection side controlled at a variety of relative humidity.

Pure iron of 50 × 50 × 1 t (mm) was used as a sample. The hydrogen penetration surface of the sample was covered with a rubber type masking material except for about 2mm diameter of bare metal area. The sample was set in the apparatus, and the relative humidity in the acrylic container was controlled by the saturated salt method. Hydrogen penetration on the entry side was accelerated by cathodic polarization at - 2 mA/cm2 for 600s in 0.1M NaOH solution. After the polarization was stopped, the surface potential distribution of the hydrogen permeation side was measured every 10 minutes to 1 hour in the range of 20 × 20 (mm) with the copper plate as a reference．

Hydrogen evolution was observed only at the bare metal area of the sample during cathodic polarization, indicating that hydrogen penetration occurred only at the area. The humidity in the acrylic container was set to 68% with a saturated potassium chloride solution, 57% by a saturated sodium chloride solution, and 38% with a saturated magnesium chloride solution, respectively. The potential on the back side of the bare pure iron area gradually went down after cathodic polarization and shifted to the noble direction after showing the maximum. It took above 24 hours at 38% RH until a return to the original surface potential distribution, and that time decreased with an increase of relative humidity. In addition, the peak value of surface potential became lower as the relative humidity decreased.
(Invited) Using Surface Chemistry to Direct the Deposition of Nano-objects for Electronics
Authors: Hedlund Jenny K. , Ellsworth Ashley A. , Walker Amy V
Published: February 2020

Nano-objects, including nanowires, nanopores, nanochannels and nanorings, and two-dimensional materials have many applications in electronics, sensing, energy conversion, optoelectronics and non-linear optics. One of the major challenges in the practical use of these structures is their integration into complex functional structures in a predictable and controlled way. In this talk we will describe our progress in synthesizing in situ with precise placement both nano-objects and films of two-dimensional materials, in particular transition metal dichalcogenides.

We have introduced two promising new techniques by which to direct the in situ growth of metallic and semiconducting nano-objects. ENDOM, or Electroless Nanowire Deposition On Micropatterned substrates, employs electroless deposition (ELD) to form metallic nanostructures on substrates. SENDOM, or Semiconductor Nanowire Deposition on Micropatterned surfaces, uses chemical bath deposition (CBD) to deposit semiconductor nanowires. Using these processes we demonstate the production of nanowires (diameters < 100 nm), mesowires (100 nm < diameter < ~3000 nm), nanorings, nanopores and nanochannels. These nanostructures can follow complex paths, such as arcs or right-angle bends, and are formed in parallel over cm2 areas. We will also discuss the formation of complex architectures, such as cross-bars, using these methods as well as the electrical properties of metallic nanowires deposited using ENDOM.

Two-dimensional materials, such as transition metal dichalcogenides (TMDs), are currently widely sought after for their application in semiconductor and nanoelectronic devices. By using templated substrates such as highly oriented pyrolytic graphite (HOPG) and sapphire we have successfully deposited large area ultra-thin molybdenum disulfide films using CBD. Further we show that the polytype of molybdenum disulfide can be altered between 2H and 1T by depositing the film on substrates with different surface energies. As the surface energy of the substrate is increased the MoS2 deposit changes from 2H to 1T. We also demonstrate that by patterning the substrate with areas of different surface energies that patterned 2H and 1T MoS2 films can be grown in situ.
(Invited) Conjugated Polymer Brushes: A New Platform to Investigate Intramolecular Charge Transport?
Authors: You Wei , Vonwald Ian
Published: February 2020

The intra-molecular transport along conjugated polymers has long been obscured by the dominant inter-molecular transport. To understand this important aspect of conjugated polymers, we have grown poly(3-methylthiophene) polymer brush films on indium tin oxide up to 120 nm thick. The morphological, structural, and electrical properties of such P3MT films were investigated. Optical and X-ray spectroscopy experiments indicate that the polymer chains have a nearly isotropic average orientation at low (< 10 nm) and high (> 30 nm) thicknesses, with mild vertical anisotropy in between. Atomic force microscopy shows that the film surfaces consist of column-shaped domains with an average cross-sectional area (2.3 × 10-3 µm2) and density (200 µm-2) that are independent of film thickness. Analysis of the contact between printed Au electrodes and the polymer brush film shows that a small fraction of the film surface (i.e., the tallest columns) makes contact with the electrodes. The measured bulk resistivity along the columns is 1.4 × 105 Ω·cm, two orders of magnitude lower than typical values for spuncast poly(3-alkylthiophene) films, while the resistance along individual polymer chains in the columns is estimated to be 360 GΩ/nm per molecule, comparable to molecular wires that exhibit charge transport by intramolecular processes. The enhanced conduction is likely due to additional intramolecular transport pathways enabled by the electrode-polymer brush-electrode device architecture, establishing conjugated polymer brushes as a platform for studying the interplay between synthesis, morphology, and charge transport phenomena.

Figure 1
(Invited) Spectroscopy and Photocurrents in All-Carbon Molecular Electronic Devices
Authors: Smith Scott R. , Najarian Amin , Supur Mustafa , McCreery Richard
Published: February 2020

One or both contacts in all-carbon molecular junctions can be sufficiently transparent to permit optical spectroscopy as a probe of device structure, and photocurrent generation to investigate photon-induced electron transport. Current-voltage (JV) curves for aromatic molecules depends strongly on molecular structure when molecular layers are more than 5 nm thick, 1 and photocurrents were used to determine structural factors determining JV behavior. 2 As shown in the left figure below, the photocurrent spectrum tracks the molecular absorption spectrum determined directly in the completed molecular junction. A molecular bilayer consisting of an electron donor and acceptor layers yields significantly higher photocurrents, which depend on the order of the layer deposition (right image below). 3 The use of photocurrents and Raman spectroscopy for characterization of molecular junction structure and operation will be discussed. 4

(1) Morteza Najarian, A.; McCreery, R. L.; Structure Controlled Long-Range Sequential Tunneling in Carbon-Based Molecular Junctions; ACS Nano
2017, 11, 3542.

(2) Morteza Najarian, A.; Bayat, A.; McCreery, R. L.; Orbital Control of Photocurrents in Large Area All-Carbon Molecular Junctions; Journal of the American Chemical Society
2018, 140, 1900.

(3) Smith, S. R.; McCreery, R.; Photocurrent, Photovoltage and Rectification in Large-Area Bilayer Molecular Electronic Junctions submitted
2018.

(4) Supur, M.; Smith, S. R.; McCreery, R. L.; Characterization of Growth Patterns of Nanoscale Organic Films on Carbon Electrodes by Surface Enhanced Raman Spectroscopy; Analytical Chemistry
2017, 89, 6463.

Figure 1
Electrochemical Removal of Copper Contamination in Anodizing Baths
Authors: Perez Eduardo ALBERTO , Rivera Fernando Felipe , antaño Lopez Rene , Torres-González Julieta
Published: February 2020

Electrolytic baths used in electroplating to make coatings or anodizing in metal parts are exposed to metal ions contamination (Cu2+, Pb2+, Zn2+ or their complexes in solution). Particularly, aluminum anodizing baths could have copper ions contamination that provoke spots and stain in the finished surface .The contamination is generated when the electrical copper connections partially lixiviates due to acid vapors generated in the process. It makes necessary to replace the bath in short periods of times and reprocess the imperfect pieces. These facts generate important economic losses.

Through the years the electrochemical technologies have been used in the treatment of contaminated effluents with metal ions, the treatment with electrochemical systems involves a challenge due to the often wide quantity of solution to be treated. The present work shows the preliminary results of copper removal from a 13% sulfuric acid bath used for aluminum anodizing, a lead cathode and 2024 aluminum pieces as anode. The experiments were carried out with a spent bath sample (with suspended solids). The concentration of copper in the solution was determinate by stripping voltammetry, as high as 200 ppm. Using XRD and ICP-MS it was found that the solids contained complexes of Cu with Pb, which means that the cathode (lead) used in the anodizing process dissolves in presence of Cu2+. The potential interval in which it is possible to carry out the deposition of copper was identified by cyclic voltammetry. The cell potential range in which it is possible to deposit copper (considering a Cu electrode as cathode and Pb electrode as anode) was calculated from the curves obtained in linear sweep voltammetry. The obtained cell potentials were then tested in a two electrodes cell configuration, and the best results were obtained at 1.3V. The copper removal achieved was 65% in 3 hours of operation.
Efficient Production of Biorenewable Monomers from Paired Electrocatalytic Hydrogenation and Oxidation of 5-(Hydroxymethyl)Furfural
Authors: Chadderdon Xiaotong , Chadderdon David J , Li Wenzhen
Published: February 2020

Electrochemical synthesis is a promising route for sustainable chemical production; however, its widespread application is hindered by low reaction rates and high energy demands. In this presentation, we report the efficient electrocatalytic conversion of 5-(hydroxymethyl)furfural (HMF) to biobased monomers by pairing HMF reduction and oxidation half-reactions in a single electrochemical cell. HMF hydrogenation to 2,5-bis(hydroxymethyl)furan (BHMF) was achieved at mild pH and ambient temperature using a self-synthesized Ag/C cathode catalyst. Meanwhile, HMF oxidation to 2,5-furandicarboxylic acid (FDCA) was facilitated with close to 100% faradaic efficiency using an inexpensive carbon felt anode together with a homogeneous nitroxyl radical catalyst. The selectivity and faradaic efficiency for Ag-catalyzed BHMF formation were sensitive to cathode potential, owing to competition from HMF hydrodimerization reactions and water reduction (hydrogen evolution). Moreover, the carbon support of Ag/C was active for HMF reduction and contributed to undesired dimer/oligomer formation at strongly cathodic potentials. As a result, high BHMF selectivity and efficiency were only achieved within a narrow potential range. Fortunately, the selectivity of nitroxyl-mediated HMF oxidation was not dependent on anode potential, thus allowing HMF hydrogenation and oxidation half-reactions to be performed together in a single cathode-potential-controlled cell. Electrocatalytic HMF conversion in the paired cell achieved high yields of BHMF and FDCA, and nearly two-fold greater overall electron efficiency compared to the unpaired cells. Future research will focus on the design of continuous-flow electrochemical reactors, in which the use of membrane electrode assemblies (MEA) may significantly lower internal resistance and further reduce total energy demands.
Optimized Process Conditions for Hydrogen Peroxide Generating Gas Diffusion Electrodes
Authors: Muddemann Thorben , Kunz Ulrich , Haupt Dennis René , Sievers Michael
Published: February 2020

Due to increasingly stringent environmental regulations for dealing with production residues, the purification of persistent residues have moved into research focus. Therefore, the inner recycling of process waters as a secondary raw material is getting continuously more relevant.

In search for new and efficient methods to purify process waters, electrochemical processes have moved to an aspiringly research emphasis. Especially electrochemical oxidation process are receiving much attention, in which strong oxidants are generated in situ, either directly on the electrode surfaces or indirectly, for instance through chemical trace substances (hypochlorite for example).

An innovative concept for removing trace elements is a combination of a boron-doped diamond electrode and a gas diffusion electrode (GDE) for generating highly oxidative species at both electrodes simultaneously. Such a system is not commercial available yet, which is mainly due to the absence of high efficient hydrogen peroxide generating gas diffusion electrodes working at greater current densities.

In addition to the challenging technical GDE design, the operating parameters strongly affect the electrochemical performance of H2O2-GDEs. While many published articles are screening electrodes under untechnical aspects with small Rotating-Ring-Disc-Electrode Systems [1, 2] or potential-controlled small scale electrolyzers [3, 4, 5], more technical-relevant scales under technical galvanostatic operation are missing.

Therefore, a technical-relevant scale of laboratory electrolysis with 100 square centimeters respectively was used, to evaluate the influence of process parameters to determine optimized operating points. The impact of current density, electrolytes pH-value, temperature (first results on the H2O2 concentration depending on temperature using 1 molar sodium hydroxide solution for a current density of 0.5 kA/m2 are presented in the diagram below) and O2 volume flow rate and the effect of the difference pressure were measured with respect to the H2O2-yield.

Finally, optimum process conditions for H2O2-producing GDE-evaluation are suggested.

References

J. F. Carneiro, R. S. Rocha, P. Hammer, R. Bertazzoli and M.R.V. Lanza, Applied Catalysis A: General,
517, 161–167 (2016).

W. R.P. Barros, R. M. Reis, R. S. Rocha and M. R.V. Lanza, Electrochimica Acta,
104, 12–18 (2013).

H. Luo, C. Li, C. Wu and X. Dong, RSC Adv,
5(80), 65227–65235 (2015).

R. S. Rocha, R. M. Reis, Beati, André A. G. F., M. R. V. Lanza, Sotomayor, Maria Del Pilar T. and R. Bertazzoli, Quím. Nova,
35(10), 1961–1966 (2012).

M. Panizza and G. Cerisola, Electrochimica Acta,
54(2), 876–878 (2008).

Figure 1
Influence of Samarium on Hydrogen Absorption during the Nickel Electrodeposition on Palladium
Authors: Flores Luis , Lopez Juan Ramon , Trejo Gabriel , Perez Jose de Jesus , Antaño López Rene , Mojica José , Meas Yunny
Published: February 2020

During the nickel electrodeposition process, secondary reactions corresponding to the reduction of a proton to Hads and the evolution of molecular hydrogen occur. The Hads could be absorbed and diffused in the substrate. In this work, we studied the effect of samarium on the process of hydrogen permeation that carries out during the electrodeposition of nickel from a nickel sulfamate bath which also contains the tensioactive SDS (sodium dodecyl sulfate). The experiments were carried out at pH 3 and T=25 ° C, with a Devanathan Starchuski cell and with different concentrations of SDS and Sm.

According to the results obtained from the permeation current and the hydrogen diffusion in the metal, we observe that additions of SDS and Sm at concentrations of 0.1g/l and 2g/l respectively will decrease the hydrogen absorption in the substrate. The influence of these additives on the mechanism of hydrogen absorption will be discussed.
Electrochemical Proton / Deuteron Separation in Nafion | Graphene | Nafion Hydrogen Pump Cells
Authors: Creager Stephen E , Bukola Saheed , Korzeniewski Carol , Harris Joel Mark
Published: February 2020

Hydrogen pump cells fabricated from Nafion membranes and Pt-on-carbon electrodes were used to measure rates of proton and deuteron transfer across single-layer graphene embedded in Nafion | graphene | Nafion sandwich structures in proton and deuteron form respectively. Ion currents up to 1 A / cm2 were obtained for proton transfer across graphene, and were diminished by a factor of 14 for otherwise identical cells pumping deuterium ions. Proton / deuterium pumping rates were nearly identical to each other for cells having no graphene. Arrhenius analysis of variable temperature studies of deuterium pumping across Nafion | graphene | Nafion membranes yielded an activation energy of approximately 0.5 +/- 0.1 eV for deuterium transfer across graphene.

Figure 1
Membrane Technologies for Renewable Energy Conversion and Storage
Authors: Xu Hui
Published: February 2020

The utilization of renewable energy has substantially driven more investments into electrolysis technologies. As renewable energy emerges and penetrates further into the energy market, the storage of surplus “off peak” electricity has received widespread attention. An electrolyzer can utilize “off peak” electricity from solar or wind farms to produce hydrogen or other fuels. These chemicals can then be operated in a fuel cell mode to generate electricity when needed or used for other industrial applications. It is estimated that the water electrolyzer market can increase up to 300 GW over the next two decades. The power to gas market alone is poised to become a multi-billion-dollar market for on-site water electrolysis systems over the next decade.

However, current hydrogen production from electrolysis comprises only a small fraction of the global hydrogen market due to the high costs that results from expensive materials even if “free” electricity from renewable energy can be acquired. Giner has been a world leader in researching, developing and manufacturing water electrolyzers and reversible fuel cells. We have been striving to develop the membrane technology to improve electrolyzers’ performance, extend their lifetimes, and lower their capital costs. These efforts include: 1) increasing membrane conductivity; 2) tailoring membrane gas and water permeability; 3) enhancing membrane mechanical strength; 4) prolonging membrane durability; 4) lowering its cost.

In addition to water electrolysis for hydrogen production, electrochemical synthesis of ammonia and CO2 conversion to hydrocarbon fuels have also been extensively investigated at Giner. Advanced membranes have been developed to enhance the conversion rate and boost the process efficiency. For example, the electrochemical production of ammonia from nitrogen and water has thus led to tremendous energy savings compared to the conventional Haber-Bosch process. The produced ammonia can be used as low-cost energy carrier for fuel cell vehicles.