bluuebunny/crossref_metadata_2025 huggingface dataset:
SEI Characterization Using Ferrocene/Ferrocenium As Redox Shuttle
Authors: Dinh Nguyen Minh-Thu , Delacourt Charles
Published: February 2020

The characterisation of the solid electrolyte interphase (SEI) formed at the negative electrode in lithium-ion batteries is proposed by Tang et al. 1 Its principle is to introduce a redox shuttle in the electrolyte after the passive film (SEI) is formed at the electrode surface and to study how the electrochemistry of the shuttle is modified by the presence of the film. It is then possible to derive some film properties such those related to the transport of the redox molecule in the film and those related to the kinetics of the shuttle oxidation/reduction. So far, the majority of the work on shuttle experiments was done on a glassy carbon electrode using ferrocene/ferrocenium as redox shuttle.

In this communication, we will describe experiments dedicated to form SEIs at glassy carbon electrodes and provide details on shuttle characterization experiments. We will show that the electrochemistry of the ferrocene/ferrocenium couple is greatly dependent on the formation charge involved in the SEI formation step. The SEI both slows down the kinetics of ferrocenium reduction (low overpotential) and also has an effect on the value of the limiting current density (high overpotential). For thin SEIs, there is a marked influence of the current density with the electrode rotation rate. Koutecky-Levich analysis can be performed on these data in order to derive the so-called kinetic current density. For electrodes on which “thick” SEIs are grown, the current density for ferrocenium reduction is much smaller and much less sensitive to the electrode rotation rate, which indicates that there is little ferrocenium diffusion limitations in the electrolyte at this low current density value. Performing Koutecky Levich analysis on these data is not possible, but the current density value measured at the RDE somehow can be considered as a direct reading of the kinetic current density.

Acknowlegdment: This work was supported by the European Union’s 7th Framework programme for research, technological development and demonstration under the SIRBATT project, which has received agreement No. 608502.

 References:

Tang, M.; Newman, J. J. Electrochem. Soc.
2011, 158(5), A530.
Unraveling the Chemical/Structural Degradation Mechanisms of Graphite/SEI in the Presence of Dissolved Manganese Ions in Lithium-Ion Batteries
Authors: Shin Hosop , Park Jonghyun , Lu Wei , Sastry Ann Marie
Published: February 2020

Understanding the degradation mechanisms of a Li-ion battery is of considerable importance for achieving a longer battery lifetime. In a Li-ion battery, the degradation process involves several physical, mechanical, and chemical processes that are interdependent. The complexity of these degradation mechanisms makes it difficult to improve the performance degradation of the battery over time, especially at elevated temperatures. Among various other reasons, the dissolution of active materials at the cathode and the resultant presence of transition metal ions in the vicinity of the anode/SEI are two of the key phenomena responsible for the degradation. While the dissolution at the cathode is effectively suppressed by the surface coating and the doping of the active materials, the degradation that occurs at the anode/SEI still remains the main challenge for Li-ion batteries due to the presence of transition metal ions (especially manganese ions). Thus, it is essential to understand how dissolved manganese ions contribute to the degradation of the anode/SEI.

Although it is obvious that the deposition of dissolved manganese ions occurs on the anode side, the nature of the precise mechanism of the interaction between the dissolved manganese ions and the anode/SEI is still being debated. In addition, the effect of dissolved manganese ions on the structural degradation of graphitic anode has not yet been systematically investigated, even if recent studies have reported the presence of manganese compounds near the graphite surface and within the graphite due to cracks or defects.

In this work, we first show how the chemical degradation of the SEI is caused by deposited manganese compounds and where the manganese is significantly distributed at the graphite/SEI. We also demonstrate that the ion-exchange reaction mechanism between inorganic SEI species and manganese ions occurs and that the identified manganese compounds at the SEI are the result of the reaction. In addition, we reveal that the surface structural disordering of the graphitic anode can be caused by dissolved manganese ions that are diffused through cracks or defects in the graphite/SEI. Density function theory (DFT) calculations are used to explain the structural effect of co-intercalated manganese ions into the graphite anode. This work sheds further light on the mechanism of capacity fading as driven by deposited manganese compounds at the anode/SEI.
(Invited) Phosphorus Complexes of Corrole
Authors: Paolesse Roberto , Naitana Mario Luigi , Nardis Sara , Pomarico Giuseppe , Stefanelli Manuela , Mandoj Federica
Published: February 2020

Metal complexes of corrole continue to attract the interest of different research groups, since the coordination chemistry of such a macrocycle presents peculiar and intriguing characteristics, such as for example its non-innocent character as a ligand.

The Periodic Table of Metallocorrolates has been widely expanded in recent years, including also main group elements. Among them, phosphorus complexes of corrole have been of particular interest, since these compounds can be easily prepared in good yields, are stable, and show unusual optical properties. For these reasons, phosphorus corroles represent a class of interesting compounds to be exploited in the field of material science or for biomedical investigations and the definition of synthetic pathways for their functionalization is an important step to optimize their properties for various applications.

We have recently developed different pathway for the selective introduction of different substituents in the peripheral positions of phosphorus triarylcorrole complexes. The characterization of such a complexes showed some peculiar properties, such as for example an unusual ruffled geometry of the corrole core, a conformation that has not been considered possible for such a macrocycle.
(Invited) Pyrrole-Based Ion-Pairing Supramolecular Assemblies
Authors: Maeda Hiromitsu
Published: February 2020

π-Electronic systems responsive to metal ions and anions are very fascinating because they can form a variety of ion complexes as building subunits, providing supramolecular assemblies that exhibit attractive electronic and electrooptical properties.[1]  In fact, anion complexes of pyrrole-based π-systems, such as dipyrrolyldiketone boron complexes and related molecules, have been found to construct ion-pairing assembled structures as solution-state aggregates, crystals, supramolecular gels, and thermotropic liquid crystals by combination with cationic species.  Derived from favorable overlap of charged π-planes, ion-pairing assemblies with the contribution of charge-segregated arrangements provided charge carrier mobilities, which are often larger than corresponding charge-by-charge-based assemblies, showing superior semi-conductive properties.  Recent achievements in arylethynyl-substituted derivatives include the formation of a variety of highly ordered structures, such as totally charge-segregated assemblies, based on [2+1]-type interlocked and [1+1]-type planar anion complexes.[2]

1. A review: Maeda, H. Bull. Chem. Soc. Jpn.
2013, 86, 1359–1399.

2. Yamakado, R.; Sakurai, T.; Matsuda, W.; Seki, S.; Yasuda, N.; Akine, S.; Maeda, H. Chem. Eur. J. in press (DOI: 10.1002/chem.201503654).
(Invited) Photodynamic Inactivation of Natural Environmental Biofilm Forming Microorganisms on Surfaces
Authors: Roeder Beate , Preuß Annegret , Borhuetter Tobias
Published: February 2020

Biofilms on outdoor walls cause aesthetic problems and economic damage. Therefore, facade paints often-containing biocides. However, commercial available biocides may have a series of adverse effects on living organisms as well as harmful environmental effects. Furthermore, biocides are increasingly designed to be more effective and are environmentally persistent. Thus, an eco-friendly and non-harmful to human health alternative to conventional biocides in wall color is strongly recommended.

This study was performed as a proof of concept for singlet oxygen generating facade paint as an alternative to conventional biocide containing facade paint for the prevention of biofilm growth on outdoor walls.

The well-known photosensitizer 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-21H,23H-porphine (TMPyP) was used as an additive in a commercially available facade paint. The generation of singlet molecular oxygen was shown using time resolved 2D measurements of the singlet oxygen luminescence. Using phototoxicity tests, we demonstrated the photodynamic activity of the photosensitizer against defined mold fungi and a mixture of microorganisms harvested from native outdoor biofilms on surfaces.

It was proven in general that it is possible to inhibit the growth of biofilm forming microorganisms growing on solid wall paint surfaces by the cationic photosensitizer TMPyP added to the facade paint using daylight conditions for illumination in 12 hours light and dark cycles.

Figure: Singlet oxygen luminescence scan of microorganisms incubated with the PS  with TMPyP. The intensity plot, which is overlayed with the picture of the sample, shows the amplitude of singlet oxygen luminescence

Figure 1
(Invited) Iron Porphyrin Alcoholate and Manganese Porphyrin Thiolate As Element-Substituted Analogs of Heme Thiolate Complex
Authors: Higuchi Tsunehiko
Published: February 2020

Cytochrome P450 plays a central role in drug metabolism and steroid biosynthesis. Among heme enzymes, cytochrome P450 and NO synthase (NOS) have strong oxidizing ability and unusual structure, in that their heme iron has thiolate coordination. We previously succeeded in synthesizing the first synthetic heme thiolate (SR complex)1 which retains thiolate coordination during catalytic oxidation and found several remarkable axial ligand effects on catalytic oxidation. However, alcoholate and selenolate ligand, which are belonged to chalcogen group same as thiolate, have not ever been examined for researching such relative effect of axial ligand by us and other investigators. Manganese porphyrin coordinated by alkanethiolate also has not yet been reported as an isolated form.

   Now we prepared the first isolable heme alcoholate 1, heme selenolate 2 and manganese heme thiolate 3 in order to investigate the effect of elemental substitution on SR complex on spectroscopic and catalytic properties. We have succeeded in the synthesis of the first heme-alcoholate complexes and the first manganese porphyrin coordinated by thiolate that can retain axial coordination during catalytic oxidizing reaction. We obtained UV-Vis spectra, FT-IR and EPR spectra of these complexes. The N-O stretching mode of complex 1-NO was 60 cm-1 higher than that of SR-NO and 38 cm-1 lower than that of an alcohol-ligated heme2. Complex 1 had 0.2 V higher E1/2 (Fe(II)/Fe(III)) than that of SR complex. These two results indicate that electron donative ability of alcoholate is much less than that of thiolate. Catalytic activity of 1 was much lower than that of SR on the oxidation of 2,4,6-tri-tert-butylphenol with perphenylacetic acid, whereas, catalytic activity of complex 3 was comparable to that of SR.

References

1. a) T. Higuchi, S. Uzu, M. Hirobe, J. Am. Chem. Soc.
1990, 112, 7051-53; b) T. Higuchi, K. Shimada, N. Maruyama, M. Hirobe, J. Am. Chem. Soc.
1993, 115, 7551-7552; c) Y. Urano, T. Higuchi, M. Hirobe, T. Nagano, J. Am. Chem. Soc.
1997, 119, 12008-12009; d) N. Suzuki, T. Higuchi, Y. Urano, K. Kikuchi, H. Uekusa, Y. Ohashi, T. Uchida, T. Kitagawa, T. Nagano, J. Am. Chem. Soc.
1999, 121, 11571-11572; e) T. Ohno, N. Suzuki, T. Dokoh, Y. Urano, K. Kikuchi, M. Hirobe, T. Higuchi, T. Nagano, J. Inorg. Biochem. 2000, 82, 123-125; f) N. Suzuki, T. Higuchi, T. Nagano, J. Am. Chem. Soc.
2002, 124, 9622-9628. g) T. Yamane, K. Makino, N. Umezawa, N. Kato, T. Higuchi Angew. Chem. Int. Ed.
2008, 47, 6438.

2.  Yi, G.-B; Chen, L.; Khan, M. A.; Richter-Addo, G. B. Inorg. Chem. 1997, 36, 3876.

Figure 1
(Invited) Peripherally Fused Azabodipy Dimers: A New Class of Near-Infrared Fluorescence Probes
Authors: D'Souza Francis , Bandi Venugopal , Gobeze Haptom B.
Published: February 2020

Photosensitizers with absorption and emission in the near-infrared (near-IR) spectral region are of great importance for diverse applications including artificial photosynthesis, high-contrast bioimaging, optical recording, near-IR laser filter, near-IR photography, photodynamic therapy and solar cells.  For example, for solar cell application, sensitizers possessing light energy harvesting capability not only in the UV-visible region but also in the near-IR region where sunlight carries over 50% of its radiation are highly desired.  Additionally, the near-IR sensitizers show marked advantages over traditionally used visible sensitizers including their ability of low light scattering and background interference, and deeper light penetration in tissues, making them the highly sought out probes in bioimaging. However, these near-IR probes often suffer from shorter excited state lifetimes and lower fluorescence quantum yields.  Hence, there is a pressing need to develop near-IR probes exhibiting higher excited state lifetime and quantum yields, accompanied by better thermal and photostability.

In the present study, we have overcome this obstacle and report a multi-step syntheses of a series of peripherally fused azaBODIPY dimers revealing fluorescence in the near-IR region (see Scheme 1 for structures).  Additionally, owing to the imposed structural rigidity (as a result of utilization of two of the peripheral aryl substituents to fuse the azaBODIPY macrocycles), the fluorescence lifetimes and quantum yields of the azaBODIPY dimers are found to be higher than their corresponding monomer analogs; thus, offering their potential utility in a range of photonic/biophotonic applications.  Details of these findings are summarized below.

Figure 1
(Invited) Trans-Substituted Benzodiazaporphyrin, a Hybrid Dye Between Porphyrins and Phthalocyanines, Opens Promising Performances in Dye-Sensitized Solar Cells
Authors: Odobel Fabrice , Andrianov Dmitry , Cheprakov Andrey
Published: February 2020

Porphyrinoid derivatives such as porphyrin and phthalocyanine have been thoroughly investigated as light collectors for photovoltaic applications, namely in dye-sensitized and organic solar cells. Benzo diazaporphyrins can be considered as hybrid dyes between porphyrins and phthalocyanines. The two interesting and valuable features of benzodiazaporphyrins is first, the presence of an intense and long wavelength absorption band like phthalocyanines, and the possibility to envision the preparation of push-pull or quadrupolar systems by trans functionalization of the two adjacent carbon meso positions. In this communication we present the synthesis and the promising photovoltaic properties of trans-substituted benzodiazaporphyrin in dye sensitized solar cells.
Synthesis and Characterization of A2B2 Tetrabenzoporphyrins
Authors: Kumar Siddhartha , Wang Hong
Published: February 2020

Benzoporphyrins have been investigated for use in a variety of applications such as dye-sensitized solar cells, photodynamic therapy and organic electronic materials1. A2B2 type porphyrins are known to exhibit non-linear optical properties2. However, there are no reports in literature of tetrabenzofused A2B2 porphyrin systems.

In this work we have synthesized novel A2B2 tetrabenzoporphyrins with electron donors on one axis and electron acceptors on the other axis. We also synthesized the corresponding A2 dibenzoporphyrins for comparison of the optical and electronic properties with the A2B2  tetrabenzoporphyrins.

(1)    Myśliwiec, D.; Donnio, B.; Chmielewski, P. J.; Heinrich, B.; Stępień, M. Journal of the American Chemical Society
2012, 134, 4822.

(2)    Nowak-Król, A.; Wilson, C. J.; Drobizhev, M.; Kondratuk, D. V.; Rebane, A.; Anderson, H. L.; Gryko, D. T.  ChemPhysChem
2012, 13, 3966.

(3)    (2)  Senge, M. O.; Fazekas, M.; Pintea, M.; Zawadzka, M.; Blau, W. J. European Journal of Organic      Chemistry    2011, 2011, 5797.

Figure 1
(Invited) Low Frequency Modes of Porphyrin Systems
Authors: Schünemann Volker
Published: February 2020

Nuclear resonance scattering is an ideal tool to study electronic and dynamic properties of iron centers in chemical and biological systems. During the last years Nuclear Resonance Vibrational Spectroscopy (NRVS) also called Nuclear Inelastic Scattering (NIS) has been used to detect iron based vibrational modes heme proteins and model complexes. We have investigated the  vibrational modes of the heme model complex  [TPPFeIII(NH2Pz)2]Cl [1], both experimentally via NRVS and theoretically by density functional theory (DFT) calculations in the region from ~5 to ~800 cm-1. DFT calculations coupled with molecular mechanics allow to investigate solvent effects. First preliminary calculations show, that the vibrational modes of [TPPFeIII(NH2Pz)2]Cl   are not significantly influenced by the solvent. In addition the effect of solvent on the low frequency modes of the NO transporter protein nitrophorin [2,3] will be presented.

This work has been supported by the research initiative NANOKAT and by the German Federal Ministry of Education and Research.

[1]       V. Schünemann, A.M. Raitsimring, R. Benda, A.X. Trautwein, T.K. Shokireva, F.A. Walker, JBIC 4 (1999) 708-716.

[2]       B. Moeser, A. Janoschka, J.A. Wolny, H. Paulsen, I. Fillipov, R.E. Berry, H. Zhang, A.I. Chumakov, F.A. Walker, V. Schünemann, J. Am. Chem. Soc. 134(9) (2012) 4216-4228.

[3]       H. Auerbach, I. Faus, S. Rackwitz, J.A. Wolny, F.A. Walker, A.I. Chumakov, H. Ogata, M. Knipp, V. Schünemann, Hyperfine Interact. 226 (2014) 439-443.
(Invited) Structure and Function of Heme Acquisition System in Corynebacterium Glutamicum
Authors: Aono Shigetoshi
Published: February 2020

Most commensal or pathogenic bacteria have heme acquisition systems for utilizing host heme as an iron source.  The heme acquisition systems consist of cell surface localized heme binding proteins and heme transport proteins.  In several Gram-positive bacteria such as Staphylococcus aureus and Bacillus anthracis, the iron regulated surface determinant (Isd) proteins capture and transfer heme to ABC transporter-type heme transport proteins.  Though a similar ABC-type heme transporter consisting of HmuT, HmuU, and HmuV proteins is used by Corynebacteria glutamicum and Corynebacterium diphtheriae, they adopt different heme binding proteins, HtaA and HtaB, instead of Isd proteins.  The ABC-type heme transporter system is widely used for heme acquisition, which consists of an ATP-binding protein, heme permease, and heme-binding protein (substrate-binding protein). In this work, we have studied the structural and functional relationships of two heme-binding proteins, HtaA and HmuT in Corynebacterium glutamicum. HtaA and HmuT act as a heme-binding protein in the heme acquisition system of HtaAB-HmuTUV for Corynebacterium glutamicum. Heme captured in HtaA is transferred into cytoplasm by the ABC-type HmuUV heme transporter, but the detailed molecular mechanisms of heme transport in these systems remain to be elucidated. In this work, the molecular mechanisms of heme acquisition in Corynebacterium glutamicum were elucidated based on the structural analyses of HtaA and HmuT.

We determined the crystal structures of an N-terminal domain of HtaA (HtaA-N) and HmuT (CgHmuT) from C. glutamicum.  Although the amino acid sequence of HtaA-N is not similar to those of Isd proteins, HtaA-N has a similar β-sandwich structure to the NEAT-domains of Isd proteins.  In HtaA-N, a single heme molecule is bound in a hydrophobic pocket with Tyr58 as the axial ligand. 

CgHmuT consists of structurally similar two domains located in the N-terminal and C-terminal regions.  A single heme molecule is bound in the cleft between these  domains.  Heme iron is ligated by His141 and Tyr240.  The details of heme environmental structure of heme-bound HmuT revealed by resonance Raman spectroscopy will be discussed.
Development of Pyrolyzed Nanoporous Carbon Electrodes with Sponge-like Networks of Mesopores for Use as Supercapacitors
Authors: Lim Yeongjin , Joo Sang Hoon , Shin Heungjoo
Published: February 2020

We developed patternable nanoporous carbon microstructures fabricated using simple O2 plasma etching and carbon-MEMS for the application of supercapacitors. Carbon-MEMS is a versatile microfabrication technology enabling batch fabrication of micro-/nano-sized carbon structure of complex architecture at a wafer level using conventional UV-lithography and pyrolysis processes.  By incorporating a simple O2 plasma etching process prior to the pyrolysis process, sponge-like networks of mesopores and nanoporous surface are formed on the top surface of pre-patterned SU-8 negative photoresist structures due to self-masking effect. These O2-plasma-treated photoresist structures are converted into nanoporous glassy carbon electrodes (average pore size = 0.56 – 0.71 nm) with sponge-like networks of mesopores via pyrolysis without using any complex nanofabrication process. As a result, the surface area and electrochemical capacitance of the nanoporous carbon surface are increased up to ~ 795 (surface area = ~ 994 m2∙g-1) and ~ 29.6 times (24.1 mF∙cm-2 at 5 mV/s) respectively compared to a bare carbon surface. In addition, arrays of 3D nanoporous carbon micro-structures such as cylinders can be simply integrated on the planar carbon electrode surface by adding a photoresist patterning process enabling further capacitance improvement up to 41.9 times. The pore size and surface morphology of the nanoporous carbon are controllable depending on O2 plasma etching time.
The Impact of Stress-Strain States on Hydrogen Flux in Martensitic Steels
Authors: Guedes Daniella , Cohendoz Stephane , Oudriss Abdelali , Bouhattate Jamaa , Thebault Florian , Creus Juan , Feaugas Xavier
Published: February 2020

The role of stress-strain states in hydrogen distribution, concentration and mobility on martensitic steel is outlined by performing tensile tests until fracture on flat, smooth, tensile specimens under simultaneous electrochemical permeation test. A specific device was designed in order to combined mechanical and electrochemical permeation (EP) experiments. Hydrogen charging was performed in sulfuric acid solution and the hydrogen detection was performed in NaOH solution.

It is demonstrated that hydrogen state can be influenced by elastic distortion at different microstructural scales related to mechanical defects (vacancies, dislocations), metallurgical components (grain boundaries, precipitates), internal and applied constraints. In additional, the mobile dislocations increase the hydrogen flux in relation with a drag process and the storage dislocations decrease the hydrogen flux in accordance with a trapping mechanism.
Effects of Hydrogen on the Surface Films Formed on Iron in Pure Water at Various Temperatures
Authors: Ejaz Ahsan , Xiao Qian , Chen Junjie , Han Guangdong , Lu Zhanpeng
Published: February 2020

The effects of hydrogen on the types, morphologies  and electrochemical properties of the surface films formed on iron in aerated pure water at 25, 40, 50 and 70 oC were investigated by  by using optical microscopy, X-ray diffraction measurements, Raman spectroscopy, electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) plots. Increasing temperature from 25 oC to 70 oC significantly accelerated the corrosion of non-charged iron. Figure 1 shows that yellow rust formed on the non-charged iron after immersion 21h at 40 oC, while the surface of hydrogen-charged iron after immersion in the same condition was gray. Figure 2 shows that the film formed on the non-charged iron after immersion 21h at 70 oC was dark, while the surface of hydrogen-charged iron after immersion in the same condition was covered with loosely distributed yellow rust particles. Raman spectra showed the different compositions of formed films on non-charged and hydrogen-charged iron specimens, as shown in Fig. 3. Normally the high valence iron oxides were formed on non-charged iron while relative low valence iron oxides were formed on the hydrogen-charged iron, with exceptions. The stability and semiconductor properties of the surface films formed on non-charged and hydrogen-charged specimens were characterized by EIS and M-S plot measurements in boric acid-borate buffere solutions, showing significant effect of hydrogen.

Figure 1
Effects of H2s and pH on Tafel Slopes in Electrochemical Corrosion of High Strength Carbon Steel S-135 in Alkaline Brines
Authors: Feng Ruishu , Beck Justin , Ziomek-Moroz Margaret , Lvov Serguei N.
Published: February 2020

Effects of H2S concentration and pH on electrochemical corrosion of high-strength low-alloy steel, Grade S-135, in NaCl-based solutions containing H2S were investigated using linear sweep voltammetry (LSV). S-135 is often used as drill pipe in oil and natural gas exploration. LSV was conducted at a scan rate of 5 mV/s in 5 %wt. NaCl solutions of pH 7.9, 10.7, and 12.4 and with four H2S partial pressures (P
H2S) ranging from 0 to 69 kPa at 85 oC after >60 hours of corrosion. Limiting current density was observed in the anodic LSV plots at lower P
H2S (0 and 0.83 kPa) but disappeared at higher P
H2S (8.3 and 69 kPa). The cathodic LSV plots did not show limiting current densities, suggesting that H2O was probably the main reactant for hydrogen evolution reaction at high pH. However, the cathodic current density increased in the presence of H2S. A modified Tafel analysis method was employed to obtain the Tafel slopes when the LSV plots were influenced by limiting current. Electrochemical reaction mechanisms have been discussed based on the anodic and cathodic Tafel slopes. Also, the corrosion rate values have been calculated using the Tafel slopes obtained from LSV and compared to those calculated with the Tafel slopes from electrochemical frequency modulation.
A Comparative Study of Cerium and Aluminum Conversion Coatings on AZ31 Magnesium Alloy in Aqueous and Ethanol Solutions
Authors: Chu Yu-Ren , Lin Chao-Sung
Published: February 2020

Regarded as a potential replacement for chromate conversion coating, cerium-based conversion coating system for magnesium alloys has been widely discussed for many years. As revealed in previous research, trivalent cerium conversion coating formed in aqueous solution is found to have a loose structure with a fibrous layer on the top, which leads to a limited barrier protection. To enhance the corrosion resistance of trivalent cerium conversion coating, some approaches that include non-aqueous system and quadrivalent cerium conversion coating have been investigated. In contrast, an aluminum conversion coating based on aluminum nitrate, which is expected to have a protection effect similar to that of cerium nitrate, has also been proposed. However, the corrosion behavior of aluminum conversion coating and its feasibility of being conducted in non-aqueous solution have not been well studied so far. Hence, this study is focused on a comparative understanding through a combination of electrochemical analysis and microstructural characterization.

Prior to conversion coating process, the AZ31 plates were abraded using emery paper up to 2500 grit and rinsed with deionized water. The conversion coating process was conducted in aqueous or ethanol solution for 60 s under room temperature, after which the coated plates were heated by hot air of approximately 75 °C for drying.

Gray coatings can be observed after both cerium and aluminum coating processes conducted in aqueous solution. As observed in electrochemical impedance spectroscopy (EIS), cerium conversion coating slightly increases the total impedance from around 5,000 to 7,000 Ωcm2 and exhibits a partially blocked electrode behavior, which is coherent with its loose microstructure. However, aluminum conversion coating shows a different behavior with an apparent barrier protection, which strongly elevates the total impedance to over 50,000 Ωcm2.

As conducted in ethanol solution, the formation of cerium and aluminum conversion coatings are both retarded. Without the existence of citric acid, aluminum conversion coating can still provide certain corrosion protection, while cerium conversion coating can barely formed. With citric acid added, however, cerium conversion coating formed in ethanol solution exhibits an impedance even higher than that of the coating formed in aqueous solution in EIS, while the total impedance of aluminum conversion coating is further decreased.
Theoretical Modeling of Erosion-Corrosion of Stainless Steel in NaCl Solution Containing Silica Sand
Authors: Zhou Xiangyang , Zheng Yugui , He Shiyu
Published: February 2020

Erosion-corrosion is an intricate interaction between mechanical damage process (e.g. solid particle impingement) and electrochemical corrosion process which generally results in severe material loss and premature equipment failure. One of the phenomena that are attracting a lot of attentions is the so-called critical flow velocity (CFV) at which the corrosion state transit from passivation to depassivation. Experimental study indicates that the CFV is a function of sand concentration, sand size, sand density, material under erosion corrosion, and polarization potential. It is envisioned that the CFV and phenomenal laws related to the CFV are keys to elucidate the mechanisms of erosion-corrosion in depth. The first level of the systematical modeling for erosion-corrosion is to define the flow field in the sand impingement apparatus using a CFD simulation tool. The second level is to give a theoretical description of the interaction between sand and the alloy surface (specifically the passivating film) based on the concepts of collision dynamics. The experimental results are analyzed using the model. The third level of the modeling is to conduct a molecular dynamics (MD) simulation to probe the damaging process in a molecular scale. The combination of the CFD and collision dynamics models correctly predicts the pattern of erosion-corrosion of the stainless steel surface under an impingement stream. The dependences of CFV on the concentration of sand and size of the particles are correctly predicted by the model. The dependence of the CFV on the applied potential can also be accounted for by the model. Further analysis indicate that the CFV has no direct relation to the breakdown of the passivating film but correlates with the balance between thinning of the passivating film by impingement and repassivation of the corrosion system. The MD modeling gives a new perspective of the effect of impingement in that the minimum impact causing film thinning by sand is the impact that eliminates the counter charges of the electric double layer (EDL) on the fluid side. The modeling work reconfirms the previous observations that erosion-corrosion is a phenomenon characterized with interactions and cross impacts among mechanical and electrochemical processes.
Deposition of Magnetite on 304 SS Under Phosphate & Caustic Treatment Regimes in Boiler Environments
Authors: Raman Balaji , Hall Derek M. , Shulder Stephen J. , Caravaggio Michael F. , Lvov Serguei N.
Published: February 2020

Under the high pressure high temperature (HPHT) conditions in boilers, iron oxides, like magnetite and hematite, are the most common corrosion products. Apart from just degrading the base metal in the feedwater system, corrosion products can also be transported downstream, where they can potentially deposit on surfaces in the boiler. Deposition of magnetite  on orifice plates in lower headers of forced circulation boilers leads to improper flow patterns, poor heat transfer and in some cases lead to tube failures. Field data suggests that the boiler operating conditions, like temperature, pressure and boiler water chemistry could influence the deposition of magnetite from the aqueous stream on to the metal surface. It has been experimentally shown previously that boiler water conditioned to pH25
⁰C 9.3 using NH4OH, favors the deposition of suspended magnetite nanoparticles on 304 stainless steel surfaces at 300 ⁰C and 100 bar. As an extension, the work presented here, explores the effects of additional chemistries on the deposition process and behavior of suspended magnetite particles. This study looks at the influence of all-volatile treatment (AVT) regime with the addition of solid alkali to the boiler water. The aim is to understand the influence of the phosphate treatment-addition of sodium triphosphate-and caustic treatment-addition of sodium hydroxide- on the deposition process with respect to the conventional AVT regime. In addition, the study also investigates the influence of solid alkali addition on the suspended magnetite and hence the nature of the deposits formed on the stainless steel substrate. The boiler environment was simulated in an autoclave pressure vessel. The test solutions were prepared in de-aerated conditions to closely match the boiler feedwater in terms of chemistry. The concentrations of sodium triphosphate and sodium hydroxide used were decided based on the standard operating guidelines followed in the industry. A standard three electrode assembly was used to monitor the deposition process using Electrochemical Impedance Spectroscopy (EIS). The nature of the deposits were investigated using surface characterization techniques. The results showed a clear influence of the zeta potential and double layer compression on the behavior of the suspended particles and their affinity to deposit at 300 ⁰C and 100 bar. The results will add to the existing work on understanding magnetite deposition and suspended particle behavior in high pressure high temperature environments.
Effects of H2s and CO2 on Cement/Casing Interface Corrosion Integrity for Cold Climate Oil and Gas Well Applications
Authors: Beck Justin , Feng Ruishu , Hall Derek M. , Buyuksagis Aysel , Ziomek-Moroz Margaret , Lvov Serguei N.
Published: February 2020

A study has been carried out to investigate sweet and sour corrosion at the cement-casing interface for offshore oil and gas wells in cold climate. The test solution chemistry was determined by sampling pore water from cement exposed in an autoclave system to brine and CO2 at 100 °C and 10 MPa. The extracted pore water was used to define the composition of a cement simulated pore solution (CSPS), which was then used for the ensuing corrosion tests. Samples made of high strength casing steel, grade Q125, were exposed to the CSPS at 4 °C and 10 MPa in CO2-only and two mixed CO2-H2S environments. The corrosion rate measured in-situ with linear polarization resistance and electrochemical impedance spectroscopy was generally found to range between 10 and 20 μm y-1 after 60 hours of exposure, with the average corrosion rate decreasing slightly with increasing H2S content. The corrosion potential, measured versus a custom high pressure Ag/AgCl electrode, was also found to shift slightly in the negative direction as the H2S content increased. The corrosion products were determined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The corrosion products had the chemical compositions close to iron carbonate and iron oxide. Sulfur was detected in the inner film region when H2S was present. These results were compared to the corrosion rates and Pourbaix diagrams modeled using commercial software. The reaction mechanisms are discussed in the paper based on the potentiodynamic polarization measurements and electrochemical impedance spectroscopy taking into account the modeled solution speciation of the CSPS and corrosion product film.
Synergistic Effect of Anodic and Organic Inhibitors on Corrosion Inhibition of Ductile Cast Iron
Authors: Kim Ki Tae , Chang Hyun Young , Lim Bu Taek , Park Heung Bae , Kim Young Sik
Published: February 2020

Organic inhibitor, in general, reveals the different inhibition mechanism to that of anodic inhibitor. When triethanolamine or nitrite added separately to water for inhibiting corrosion of ductile cast iron, huge amounts of inhibitor should be needed because the corrosion inhibitors have to overcome the galvanic corrosion between graphite and matrix. This work used ductile cast iron and corrosion properties were evaluated in a tap water with/without inhibitors. Corrosion rate was measured using chemical immersion test and also electrochemical methods including anodic polarization test were performed. Inhibited surface was analyzed using EPMA and XPS. Test solutions were analyzed using a FT-IR measurement. When triethanolamine and nitrite coexist in water, synergistic effect built up and thus their mixed concentration was reduced to about 1/30 times than single addition. This work focused on synergistic effect by nitrite and triethanolamine and its mechanism was newly proposed (This work was supported by the Nuclear Power Core Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20131520000100).).
Corrosion and Redox Potential Control of High Temperature Materials in Fluoride and Chloride Molten Salts
Authors: Fuentes Roderick Eliel , Olson Luke Christopher , Martinez-Rodriguez Michael Joe , Gray Joshua R. , Garcia-Diaz Brenda Lee
Published: February 2020

Concentrating solar power (CSP) systems that can operate at higher temperatures can achieve higher efficiencies and power production using high temperature power cycles.  Operating at these higher temperatures requires identifying heat transfer fluids and materials of construction for heat transfer systems that will provide good operating characteristics and long system lifetimes under these conditions. Advanced power cycles such as the supercritical CO2 Brayton cycle can operate above 800°C and molten salts are one of the best options to transfer heat at these conditions due to their very high boiling points and good heat transfer properties.  However, a potential drawback with using high temperature molten halide salts is materials corrosion.  Therefore, it is important to identify pairs of heat transfer materials and molten salts that will have the mechanical properties and chemical stability that will provide long system lifetimes. Several alloys that can be used for high temperature operation includes alloys with high nickel and chromium content, such as Haynes 230, and high cobalt and chromium content, such as Haynes NS-163. However, weight loss by dealloying of Cr from high temperature alloys containing Cr was observed. In this work, several high temperature alloys were exposed to molten KCl-MgCl2 and FLiNaK (LiF-NaF-KF) at several temperatures ranging from 750 to 950 °C for 100 hours. For redox potential control, Mg and Zr were added into the test. The alloys were examined via SEM/EDS post corrosion at the surface and cross-section to account for the corrosion attack and element depletion from bulk. The salts were analyzed via ICP-OES to quantify the elements that were depleted and diffused into the salt.
Electrochemical Study of Corrosion in High Temperature Molten Salts
Authors: Garcia-Diaz Brenda Lee , Olson Luke Christopher , Martinez-Rodriguez Michael Joe , Fuentes Roderick Eliel , Gray Joshua R.
Published: February 2020

Concentrating solar power systems are projected to need to produce energy with a cost of $0.06/kWh when implemented on a very large scale.  It is generally believed that temperatures of the heat transfer fluids will need to be higher than 800oC to drive an advanced Brayton cycle or Rankine cycle with superheated steam to reach this target.  However, current state-of knowledge of corrosion science indicates a lack of published data on the impact of molten salts at temperatures above 800°C on corrosion of molten salt contacting materials such as steels or high temperature alloys and ceramics. This work investigates the corrosion mechanism of selected alloys and ceramics in chloride and fluoride molten salts used for high operating temperature heat transfer fluids using a combination of electrochemical techniques, theoretical calculations, and thermodynamic predictions. The electrochemical characterizations included linear polarization resistance scans, electrochemical impedance spectroscopy, and cyclic potentiodynamic polarization.  Results show that the Fe-Ni-Cr alloys tested have high general corrosion and require corrosion inhibition. Advanced materials, such as SiC-SiC and TZM, have been shown to have much lower corrosion and good passivation behavior.  Experimental tests using coupon immersion in the molten salts support the mechanism determined from electrochemical testing that the main element being oxidized is Cr. Analysis of samples also indicates selective Cr oxidation concentrates along grain boundaries and creates porous networks in the sample. The electrochemical impedance tests suggest that the corrosion is diffusion controlled and this assumption correlates well with corrosion modeling studies.  The electrochemical testing data combined with thermodynamic modeling led to the development of a reaction mechanism for high temperature corrosion in molten salts.
The Effect of Nickel Alloy Corrosion Under Cathodic Protection inside High Temperature Molten Salt Systems
Authors: Tavakoli Bahareh Alsadat , Shimpalee Sirivatch , Weidner John W. , Garcia-Diaz Brenda L. , Martinez-Rodriguez Michael J. , Olson Luke Christopher
Published: February 2020

One way to potentially reduce the costs of concentrated solar power (CSP) central receiver systems is to operate the central receiver at high temperatures that allow for more efficient thermodynamic power conversion cycles. Molten salts are one potential heat transfer fluid at that can operate efficiently at these temperatures, but their use will introduce other technological challenges, such as corrosion and mass transfer reactions.  The corrosion of alloys at high-temperature (700-1000°C) in the receivers and heat exchangers cause a reduction in heat transfer efficiency and durability. Cathodic protection may mitigate corrosion of metal surfaces by shifting the potential of the alloy below its oxidation potential.  The behavior of molten salt cooled concentrated solar power (CSP) systems under cathodic protection can be obtained by developing a 3-D model. A simplified model was designed for and benchmarked against a  thermosiphon reactor.  This thermosiphon reactor exposed alloy coupons to non-isothermal conditions expected in concentrated solar power (CSP) plants. When the cathodic current density is equal to the protection current density and the potential is a protective, the model calculates the corrosion rate and the corrosion potential. Magnesium was used as a sacrificial anode. The rate of Mg consumption, the corrosion potential, and the corrosion current are dependent on several studied variables. Kinetic parameters were obtained from experimental coupon exposures conducted between 700-1000 °C in molten salt in the thermosiphon reactor.  Results were in good agreement with experimental values at different conditions.

     Fig. 1 shows a comparison of the model prediction of corrosion rate distribution, i (A/cm2) at coupon surfaces for both Hot-Zone and Cold- Zone without (a) and with (b) cathodic protection.

Acknowledgements

The authors gratefully acknowledge the financial support for this work from the DOE EERE SunShot Initiative (DE-AC36-08GO28308) under a subcontract from SRNL to the University of South Carolina. The authors also thank the University of South Carolina Center for Fuel Cells and the CD-adapco group for their support.

Figure 1
The Technology of Corrosion Control with Corrosion Inhibitors in Water Pipes
Authors: Park Young-bog , Choi Young-june , Park Eunhee , Lee Jinsuk , Park Ju-hyun , Min Byungdae , Huh Yujeong , Choi In-cheol , Chung Hyen-Mi
Published: February 2020

Introduction

The principle oxidants in the drinking system are dissolved oxygen and chlorine, and the corrosion of water pipe is going alone because of oxidants reaction. Since 1930, pH control chemicals such as NaOH, Ca(OH)2, NaHCO3, and phosphate corrosion inhibitors have been used to prevent the corrosion of water pipes. However, to directly add Ca(OH)2at inlet of water well in production process of drinking water may cause a problem to make clouding phenomenon in tap water. The objective of this study removes such problems as the turbidity, strengthen more safety of water.

Experimental

Materials – The iron(carbon steel) was in the form of sheet 0.04 cm in thick and the following analysis: Fe 99.62%, Mn 0.26%, Cu 0.08%, Ni 0.05%, Mo 0.01%. specimens cut from this sheet measured 15cm×1.2cm. The chemicals used as corrosion inhibitors were NaOH, Ca(OH)2, and H3PO4 and tap water used as blank. NaOCl was used to disinfect the drinking water made by the demo plant.  In order to examine the effect of disinfectant residual concentration according to adding lime water and corrosion inhibitor such as ortho phosphate(H3PO4), the residual concentration of disinfectant was measured in carbon steel water pipe 50 m in length at the corrosion pilot plant and the temperature of solution was in room temperature between 5°C in the winter to 35°C in the summer. Chlorine residual concentration in the water pipes 50 m in length was measured for 5, 10, 20, 40, 60 min, respectively. The electrochemical tests was measured using Solartron Potentiostat 1480 and the test was performed  in a typical three electrode cell which consist of carbon steel as working electrode, saturated calomel electrode as reference electrode, platinum counter electrode.

Result
s

HOCl and OCl- in drinking water which chlorine was added as disinfectant reach in equilibrium state at nearly pH 7.5. As pH increases, more of OCl- exists than the strong disinfectant, HOCl-, Increasing HOCl below pH 7.5 is more benefit in terms disinfectant efficiency. Figure 2 above shows the concentration of free residual chlorine with time. Running drinking water in the pipe, adding PO4 decreased concentration of chlorine from 0.48 to 0.28 ppm for 40 min, NaOH decreased concentration of chlorine from 0.45 to 0.10ppm, Ca(OH)2 decreased concentration of chlorine from 0.24 to 0.10 ppm, but tap water as blank degreased concentration of chlorine from 0.40 to 0.07 ppm for only 10 minutes. Of three corrosion inhibitors, PO4 showed the highest reduced efficiency for the concentration of residual chlorine. To inhibit the reaction of chlorine with metal water pipe is similar to inhibit the corrosion reaction.

Reference

US EPA, Disinfection Profiling and Benchmarking, EPA Guidance Manual, August 1999.

American Society for Testing and Materials, G 4-95(1996).

Figure 1