A mechanistic study on the hydrogen trapping property and the subsequent electrochemical corrosion behavior of quenched and tempered steel

Kim, Sung Jin,Park, Jin Sung,Hwang, Eun Hye,Ryu, Seung Min,Seong, Hwan Goo,Cho, Yeol Rae Elsevier 2018 International journal of hydrogen energy Vol.43 No.37

<P><B>Abstract</B></P> <P>The hydrogen-facilitated anodic dissolution of steel is an interesting experimental phenomenon, but the persistent gaps in this knowledge area are great. The changes in the Tafel slopes and the reaction rates of steel that has been cathodically charged with hydrogen are interpreted mainly in the context of hydrogen trapping and de-trapping behaviors of steel using a variety of electrochemical methods. This study reveals that the increase in the anodic current density and the decrease in the polarization resistance are attributed primarily to the hydrogen-induced lattice expansion. Based on the Tafel-slope change, the oxidation of hydrogen cation partly contributed to the increase in the total anodic current density together with the dominant anodic reaction of the steel dissolution. The electrochemical permeation measurements showed much slower effusion kinetics of the hydrogen that has been trapped at the ε-carbide particles, and the trapping and de-trapping behavior at the fine particles are one of the controlling factors of the hydrogen-enhanced anodic dissolution of steel. From an engineering aspect, it is believed that the current study will provide an important insight into future perspectives on stress corrosion cracking failure occurring in various high-strength steels.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogen-facilitated anodic reactions of steel are demonstrated experimentally. </LI> <LI> Effect of fine precipitates (ε-carbide) on hydrogen effusion kinetics is discussed. </LI> <LI> The presence of atomic hydrogen in the steel lattice contributes to lattice expansion. </LI> <LI> Anodic and cathodic reaction rates depend on hydrogen charging and subsequent aging. </LI> <LI> Hydrogen trapping at ε-carbide particles leads to slower hydrogen effusing kinetics. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Thickness Dependence of Size and Arrangement in Anodic TiO_2 Nanotubes

Sunmi Kim,Byung Gun Lee,최진섭 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.10

The degree of self-assembly and the size variation of nanotubular structures in anodic titanium oxide prepared by the anodization of titanium in ethylene glycol containing 0.25 wt % NH4F at 40 V were investigated as a function of anodization time. We found that the degree of self-assembly and the size of the nanotubes were strongly dependent on thickness deviation and thus indirectly on anodization time, as the thickness deviation was caused by the dissolution of the topmost tubular structures at local areas during long anodization. A large deviation in thickness led to a large deviation in the size and number of nanotubes per unit area. The dissolution primarily occurred at the bottoms of the nanotubes (D_(bottom)) in the initial stage of anodization (up to 6 h), which led to the growth of nanotubes. Dissolution at the tops (D_(top)) was accompanied by D_(bottom) after the formed structures contacted the electrolyte after 12 h, generating the thickness deviation. After extremely long anodization (here, 70 h), D_(top) was the dominant mode due to increase in pH, meaning that there was insufficient driving force to overcome the size distribution of nanotubes at the bottom. Thus, the nanotube array became disorder in this regime.

Thickness Dependence of Size and Arrangement in Anodic TiO₂ Nanotubes

Kim, Sun-Mi,Lee, Byung-Gun,Choi, Jin-Sub Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.10

The degree of self-assembly and the size variation of nanotubular structures in anodic titanium oxide prepared by the anodization of titanium in ethylene glycol containing 0.25 wt % $NH_4F$ at 40 V were investigated as a function of anodization time. We found that the degree of self-assembly and the size of the nanotubes were strongly dependent on thickness deviation and thus indirectly on anodization time, as the thickness deviation was caused by the dissolution of the topmost tubular structures at local areas during long anodization. A large deviation in thickness led to a large deviation in the size and number of nanotubes per unit area. The dissolution primarily occurred at the bottoms of the nanotubes ($D_{bottom}$) in the initial stage of anodization (up to 6 h), which led to the growth of nanotubes. Dissolution at the tops ($D_{top}$) was accompanied by $D_{bottom}$ after the formed structures contacted the electrolyte after 12 h, generating the thickness deviation. After extremely long anodization (here, 70 h), $D_{top}$ was the dominant mode due to increase in pH, meaning that there was insufficient driving force to overcome the size distribution of nanotubes at the bottom. Thus, the nanotube array became disorder in this regime.

Mitigating Metal-dissolution in a High-voltage 15 wt% Si-Graphite‖Li-rich Layered Oxide Full-Cell Utilizing Fluorinated Dual-Additives

Kim, Jaeram,Kwak, Sehyun,Pham, Hieu Quang,Jo, Hyuntak,Jeon, Do-Man,Yang, A-Reum,Song, Seung-Wan The Korean Electrochemical Society 2022 Journal of electrochemical science and technology Vol.13 No.2

Utilization of high-voltage electrolyte additive(s) at a small fraction is a cost-effective strategy for a good solid electrolyte interphase (SEI) formation and performance improvement of a lithium-rich layered oxide-based high-energy lithium-ion cell by avoiding the occurrence of metal-dissolution that is one of the failure modes. To mitigate metal-dissolution, we explored fluorinated dual-additives of fluoroethylene carbonate (FEC) and di(2,2,2-trifluoroethyl)carbonate (DFDEC) for building-up of a good SEI in a 4.7 V full-cell that consists of high-capacity silicon-graphite composite (15 wt% Si/C/CF/C-graphite) anode and Li_1.13Mn_0.463Ni_0.203Co_0.203O₂ (LMNC) cathode. The full-cell including optimum fractions of dual-additives shows increased capacity to 228 mAhg^-1 at 0.2C and improved performance from the one in the base electrolyte. Surface analysis results find that the SEI stabilization of LMNC cathode induced by dual-additives leads to a suppression of soluble Mn²⁺-O formation at cathode surface, mitigating metal-dissolution event and crack formation as well as structural degradation. The SEI and structure of Si/C/CF/C-graphite anode is also stabilized by the effects of dual-additives, contributing to performance improvement. The data give insight into a basic understanding of cathode-electrolyte and anode-electrolyte interfacial processes and cathode-anode interaction that are critical factors affecting full-cell performance.

Anodic Dissolution Behavior of Zr-Nb Alloy in Chloride-based Molten Salts

Jungho Hur,Yeonghwan Jeon,Seungmin Ohk,Jaeyeong Park 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

Zirconium(Zr) alloys are commonly used in the nuclear industry for applications such as fuel cladding and pressure tubes. To minimize the levels and volumes of radioactive waste, molten salts have been employed for decontaminating Zr alloys. Recently, a two-step Zr metal recovery process, combining electrolysis and thermal decomposition, has been proposed. In the electrolysis process, potentiostatic electrorefining is utilized to control the chemical form of electrodeposits(ZrCl). Although Zr metals are expected to dissolve into molten salts, reductive alloy elements can also be co-dissolved and deposited on the cathode. Therefore, a better understanding of the anodic side’s response during potentiostatic electrorefining is necessary to ensure the purity of recovered Zr and long-term process operation. As the first step, potentiodynamic polarization curves were obtained using Zr, Nb, and Zr-Nb alloy to investigate the anodic dissolution behavior in the molten salts. Nb, which has a redox potential close to Zr, and Zr exhibit active or passivation dissolution mechanisms depending on the potential range. It was confirmed that Zr-Nb alloy also has a passivation region between -0.223 to -0.092 V influenced by the major elements Zr and Nb. Secondly, active dissolution of Zr-Nb was performed in the range of -0.9 to -0.6 V. The dissolution mechanism can be explained by percolation theory, which is consistent with the observed microstructure of the alloy. Thirdly, passivation dissolution of Zr, Nb, and Zr-Nb alloy was investigated to identify the pure passivation products and additional products in the Zr-Nb alloy case. K2ZrCl6 and K3NbCl6 were identified as the pure passivation products of the major elements. In the Zr-Nb alloy case, additional products, such as Nb and NbZr, produced by the redox reaction of nanoparticles in the high viscous salt layer near the anode, were also confirmed. The anodic dissolution mechanism of Zr-Nb alloy can be summarized as follows. During active dissolution, only Zr metal dissolves into molten salts by percolation. Above the solubility near the anode, passivation products begin to form. The anode potential increases due to the disturbance of passivation products on ion flow, leading to co-dissolution of Nb. When the concentration of Nb ion exceeds the solubility, a passivation product of Nb also forms. In this scenario, a high viscous salt layer is formed, which traps nanoparticles of Zr metal, resulting in redox behavior between Zr metal and Nb ion. Some nanoparticles of Zr and Nb metal are also present in the form of NbZr.

아르곤 분위기의 NaCl 수용액에서 구리의 산화 용해반응에 미치는 염화이온의 영향

천정균,김연규,Chon, Jung-Kyoon,Kim, Youn-Kyoo 한국전기화학회 2008 한국전기화학회지 Vol.11 No.3

변전위법, 순환전압전류법, 대시간전류법 및 대시간전기량법을 이용하여 구리의 산화 용해반응에 미치는 $Cl^-$의 영향을 조사하였다. 아르곤 분위기의 NaCl 수용액에서 Cu의 산화 용해반응은 전반응식 $Cu+2Cl^{-}{\rightleftharpoons}{CuCl_2}^{-}+e^-$ 에 따라 일어나며, Cu 표면에 $Cl^-$가 흡착하는 과정에 잘 맞는 등온식은 Temkin 흡착등온식 임을 알 수 있었다. We investigated chloride ion effects on anodic dissolution of copper using potentiodynamic method, cyclic voltammtery, chronoamperometry and chronocoulometry. The anodic dissolution reaction of copper in NaCl solution under argon atmosphere is $Cu+2Cl^{-}{\rightleftharpoons}{CuCl_2}^{-}+e^-$ and chloride ion adsorption process in copper surface can be explained by Temkin isotherm.

전기응집을 위한 알루미늄 양극용출반응에 관한 연구

김학준 경남대학교 환경문제연구소 2002 환경연구 Vol.25 No.-

Generally, metal was well formed metallic oxide film in atmosphere or aqueous solution, especially aluminum showed obviously this phenomenon. Therefore, in this study, when anodic dissolution was dont by using various electrolyte and cathode, mechanism of anodic dissolution reaction was examined. As a consequence, oxide film of aluminum surface was dissolved together with the dissolution reaction of metal by the anodic current. It was shown that the dissolution reaction due to the contact between electrolyte and metal happened in the same time.

The Kinetics of Anodic Dissolution and Repassivation on 316L Stainless Steel in Borate Buffer Solution Studied by Abrading Electrode Technique

( H S Xu1 ),( D B Sun ),( H Y Yu ),( H M Meng ) 한국부식방식학회(구 한국부식학회) 2015 Corrosion Science and Technology Vol.14 No.6

The capacity of passive metal to repassivate after film damage determines the development of local corrosion and the resistance to corrosion failures. In this work, the repassivation kinetics of 316L stainless steel (316LSS) was investigated in borate buffer solution (pH 9. 1) using a novel abrading electrode technique. The repassivation kinetics was analyzed in terms of the current density flowing from freshly bare 316L SS surface as measured by a potentiostatic method. During the early phase of decay (t < 2 s), according to the Avrami kinetics-based film growth model, the transient current was separated into anodic dissolution (idiss) and film formation (ifilm) components and analyzed individually. The film reformation rate and thickness were compared according to applied potential. Anodic dissolution initially dominated the repassivation for a short time, and the amount of dissolution increased with increasing applied potential in the passive region. Film growth at higher potentials occurred more rapidly compared to at lower potentials. Increasing the applied potential from 0 VSCE to 0. 8 VSCE resulted in a thicker passive film (0. 12 to 0. 52 nm). If the oxide monolayer covered the entire bare surface (θ=1), the electric field strength through the thin passive film reached 1. 6 × 107 V/cm.

Effect of Electrolytes on Electrochemical Properties of Magnesium Electrodes

Ha, Se-Young,Ryu, Anna,Cho, Woosuk,Woo, Sang-Gil,Kim, Jae-Hun,Lee, Kyu Tae,Kim, Jeom-Soo,Choi, Nam-Soon The Korean Electrochemical Society 2012 Journal of electrochemical science and technology Vol.3 No.4

Magnesium (Mg) deposition and dissolution behaviors of 0.2 M $MgBu_2-(AlCl_2Et)_2$, 0.5 M $Mg(ClO_4)_2$, and 0.4M $(PhMgCl)_2-AlCl_3$-based electrolytes with and without tris(pentafluorophenyl) borane (TPFPB) are investigated by ex situ scanning electron microscopy (SEM) and galvanostatic cycling of Mg/copper (Cu) cells. To ascertain the factors responsible for the anodic stability of the electrolytes, linear sweep voltammogrametry (LSV) experiments for various electrolytes and solvents are conducted. The effects of TPFPB as an additive on the anodic stability of 0.4M ($(PhMgCl)_2-AlCl_3$/THF electrolyte are also discussed.

Phthalate 완충용액에서 전해 석출한 철족 원소의 산화 용해 반응

천정균,김연규,Chon, Jung-Kyoon,Kim, Youn-Kyoo 대한화학회 2007 대한화학회지 Vol.51 No.1

금(Au) 전극 위에 전해 석출한 철족 원소(Fe, Co, Ni)를 전극으로 phthalate 완충 용액에서 철족 원소의 부식과정을 조사하였다. Phthalate 완충용액의 pH의 변화에 대한 부식전위와 부식전류를 측정하여 각 원소(Fe, Co, Ni)전극의 산화반응과 환원반응에 대한 Tafel 기울기를 구하였으며 Tafel 기울기를 포함한 정량적인 전기화학 인자를 측정하여 전극의 산화반응과 환원반응에 대한 반응 메커니즘을 제안하였다. Phthalate 완충 용액에 존재하는 화학 종의 흡착은 철족 원소 전극의 산화반응에 영향을 미치는 것으로 보인다. The anodic dissolution of electrodeposited iron group elements (Fe, Co, Ni) were studied in phthalate buffer solution. The pH dependence of the corrosion potential, the corrosion current and Tafel slope was measured for each element. Based on the electrochemical parameters including Tafel slopes, we proposed the redox mechanism of the corrosion and the passivation. The adsorption of various phthalate species on the electrodeposited iron group elements seemed to be affected the corrosion mechanisms.