Education 【 display / non-display 】

Education 【 display / non-display 】

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  1970

  Waseda University  

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  1970

  Waseda University   Graduate School, Division of Science and Engineering  

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  1968

  Waseda University   School of Science and Engineering  

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  1968

  Waseda University   Faculty of Science and Engineering  

Degree 【 display / non-display 】

Degree 【 display / non-display 】

• The University of Tokyo   (BLANK)

• Waseda University   (BLANK)

Research Experience 【 display / non-display 】

Research Experience 【 display / non-display 】

• 1970

  -

  1999

  日本鋼管(株)研究員

• 1970

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  1999

  Research Scientist of NKK

Professional Memberships 【 display / non-display 】

Professional Memberships 【 display / non-display 】

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  （社）日本保全学会

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  （一社）日本原子力学会

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  （一社）表面技術協会

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  （公社）化学工学会

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  （一社）日本鉄鋼協会

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Research Areas 【 display / non-display 】

Research Areas 【 display / non-display 】

• Material processing and microstructure control

• Structural materials and functional materials

• Biomaterials

• Biomedical engineering

Papers 【 display / non-display 】

Papers 【 display / non-display 】

• After-effects induced by interactions between hydrogen and the martensite transformation in Ni-Ti superelastic alloy

  Ken'ichi Yokoyama, Yuki Hirata, Jun'ichi Sakai

  PHILOSOPHICAL MAGAZINE LETTERS   97 ( 9 ) 350 - 358  2017  [Refereed]

  　View Summary

  The effects of dynamic interactions between hydrogen and a stress-induced martensite transformation on the recovery of deteriorated tensile properties by ageing in air at room temperature have been investigated for a Ni-Ti superelastic alloy. A specimen is subjected to single stress-induced martensite and reverse transformations immediately after hydrogen charging. Upon tensile testing, brittle fracture occurs in the latter half of the elastic deformation region of the martensite phase after the stress-induced martensite transformation. Upon ageing before the tensile test, fracture occurs during the stress-induced martensite transformation. In addition, the nano- and micro-morphologies of the brittle outer part of the fracture surface of the specimen are changed by ageing. Thus, the tensile properties markedly deteriorate, rather than recover, by ageing. The present results clearly indicate that dynamic interactions between hydrogen and the stress-induced martensite transformation have serious after-effects on hydrogen embrittlement of Ni-Ti superelastic alloy.

  DOI

• Effects of temperature, phase, elastic deformation and transformation on inhibition of localized corrosion of hydrogen-charged Ni-Ti superelastic alloy in NaCl solution

  Shigekazu Nishimoto, Ken'ichi Yokoyama, Toshiaki Inaba, Kenichiro Mutoh, Jun'ichi Sakai

  JOURNAL OF ALLOYS AND COMPOUNDS   682   22 - 28  2016.10  [Refereed]

  　View Summary

  The effects of the solution temperature, phase, elastic deformation and the phase transformation on the inhibition of localized corrosion of a small amount of hydrogen-charged Ni-Ti superelastic alloy in 0.9% NaCl solution have been investigated by electrochemical measurements. No pitting potentials are observed in the anodic polarization curves obtained above room temperature and under static applied stress in the presence of parent or stress-induced martensite phases. In a dynamic cyclic tensile test in the elastic deformation region of the parent phase under various constant applied anodic potentials, the critical applied potential for an increase in the current density, which corresponds to the occurrence of localized corrosion, considerably shifts in the noble direction. At the stress plateau, i.e., in the superelastic region, caused by stress-induced martensite and reverse transformations, the critical applied potential for a marked increase in the current density slightly shifts in the noble direction. In the elastic deformation region of the stress-induced martensite phase, the critical applied potential for a marked increase in the current density shifts in the noble direction. The present results indicate that hydrogen charging is effective for inhibiting the localized corrosion of Ni-Ti superelastic alloy in NaCl solution at various temperatures, irrespective of the phase itself, under dynamic elastic deformation and the phase transformation. (C) 2016 Elsevier B.V. All rights reserved.

  DOI

• Inhibition of localized corrosion of Ni-Ti superelastic alloy in NaCl solution by hydrogen charging

  Ken'ichi Yokoyama, Yuki Hirata, Toshiaki Inaba, Kenichiro Mutoh, Jun'ichi Sakai

  JOURNAL OF ALLOYS AND COMPOUNDS   639   365 - 372  2015.08  [Refereed]

  　View Summary

  Inhibition of the localized corrosion of Ni-Ti superelastic alloy in 0.9% NaCl solution has been attempted by charging with a small amount of hydrogen, which causes negligible hydrogen embrittlement. Upon a small amount of hydrogen charging, no pitting potential is observed in anodic polarization curves. From scanning electron microscope observations, localized corrosion is inhibited on the entire side surface of charged specimens. With increasing amount of charged hydrogen, the corrosion potential shifts in the less noble direction and the current density increases under anodic applied potential. When the hydrogen charged specimens are aged in the atmosphere at room temperature, the corrosion potential becomes almost the same as that of the non-charged specimen, but the inhibition of localized corrosion remains. The present study indicates that a small amount of hydrogen charging is effective for inhibiting the localized corrosion of the alloy in NaCl solution. (C) 2015 Elsevier B. V. All rights reserved.

  DOI

• Electrochemical study on corrosion inhibition effect of Mannich-modified phenolic resin coating on galvanized steel

  Ryosuke Sako, Jun'ichi Sakai

  Zairyo to Kankyo/ Corrosion Engineering   64 ( 10 ) 466 - 474  2015  [Refereed]

  　View Summary

  The mechanism of corrosion inhibition of Mannich-modified phenolic resin coating which is one of the alternatives to chromate conversion coating on the electrogalvanized steel sheet was investigated by cross-section analysis and electrochemical measurements of the coating film. The 200°C cured coating film which has good corrosion inhibition has the higher charge transfer resistance (Rct) and the higher film resistance (Rf) calculated by electrochemical impedance measurement than the 80 °C cured coating film. The increase of these resistances is due to decrease of water absorption property of the film caused by crosslinking reaction. Namely the film resistance is enhanced by reduction of ionic conductivity of the film, and the charge transfer resistance is enhanced by reduction of the supply of the water containing dissolved oxygen to interface between the film and substrate. The phosphoric acid added to coating solution forms an insoluble zinc phosphate coating layer at the coating / material interface. The zinc phosphate coating layer, which is formed in close contact with the complex surface shape of the substrate by chemical interaction with the substrate surface by chemical interaction with the material surface, enhances the barrier effect to obstruct the contact of substrate with the water containing dissolved oxygen. Consequently the corrosion inhibition of the coating film is excellent. On the other hand, the 80°C cured coating film without phosphoric acid, which has no chemical interaction with the substrate, has some voids (defects) at film /substrate interface and its corrosion inhibition is inferior.

  DOI

• Dissolution Behavior of Duplex Stainless Steels in Crevice Corrosion Growth Step

  So Aoki, Yushi Nada, Jun'Ichi Sakai

  Zairyo to Kankyo/ Corrosion Engineering   64 ( 8 ) 366 - 372  2015  [Refereed]

  　View Summary

  The objective of this study is to clarify dissolution behavior of duplex stainless steels in crevice corrosion growth step. Crevice corrosion grew on the duplex stainless steels by holding potential at various values. After a certain period, dissolution behavior of the crevice corrosion was analyzed based on observation of corroded area. Change in crevice corrosion dissolution behavior with time was also investigated by means of in-situ observation. Four types of dissolution regions could be observed in the corrosion area from outside toward inside direction, i.e., tip of the corroded area toward initiation point, in a crevice
  they were passive region, the preferential dissolution region of γ phase, α phase and γ phase dissolution region, and the preferential dissolution region of α phase. The crevice corrosion which maintained that four dissolution regions grew toward the edge of the crevice. This dissolution behavior was given at all the potential where crevice corrosion occurred.

  DOI

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Books and Other Publications 【 display / non-display 】

Books and Other Publications 【 display / non-display 】

• 鉄鋼便覧 第5版

  2014

• 社団法人 日本機械学会編 ＪＳＭＥテキストシリーズ 『機械材料学』

  日本機械学会  2008

• 電子機器部品の腐食・防食Q&A 腐食防食協会編

  丸善  2006

• 改訂 4版 化学工学辞典 化学工学会編

  丸善  2005

• 金属の腐食防食Q&A コロージョン１１０番 電気化学入門編

  2003

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Misc 【 display / non-display 】

Misc 【 display / non-display 】

• ステンレス鋼の耐発銹性に及ぼす不働態被膜の安定度の影響

  富士浩行, 青木聡, 石井知洋, 酒井潤一

  材料と環境   64 ( 5 ) 178 - 182  2015

• Corrosion behavior of carbon steels coupled to stainless steels in sea water

  Hirotaka Sato, Toru Yamaji, Jun'ichi Sakai

  Zairyo to Kankyo/ Corrosion Engineering   64 ( 5 ) 183 - 187  2015

  　View Summary

  To evaluate the corrosion risk of offshore steel structures at submerged zone caused by stainless steel sheathing and cathodic protection failures, it is essential to grasp the degree of the carbon steel-stainless steel galvanic corrosion. The objective in this study was to clarify the effect of area ratio of stainless steel coupled to carbon steel on corrosion behavior in sea water. As a result, stainless steels promote galvanic corrosion, but the degree of accelerated corrosion was much smaller than that estimated from the area ratio. Calcareous deposits had formed on the surface of stainless steels during galvanic tests in seawater. The calcareous deposits appeared to diminish the diffusion of the dissolved oxygen and diminish the cathodic reaction of oxygen reduction on the stainless steel surface.

  DOI

• 恒温硫黄蒸気環境の銀の硫化挙動におよぼす銀表面温度の影響

  稲葉康介, 石川雄一, 酒井潤一

  材料と環境   64 ( 5 ) 188 - 192  2015

• Creep corrosion cracking of Sn-3.0Ag and Sn-0.5Cu solder alloys in NaCl solution

  Ken'ichi Yokoyama, Akihide Nogami, Jun'ichi Sakai

  CORROSION SCIENCE   86   142 - 148  2014.09

  　View Summary

  The surface crack nucleation of Sn-3.0Ag and Sn-0.5Cu solder alloys has been examined by performing sustained tensile-loading tests in 0.9 mass% NaCl solution at room temperature. For Sn-3.0Ag alloy, many cracks nucleate and propagate on the side surface of the specimen, similarly to Sn-3.0Ag-0.5Cu alloy reported previously. For Sn-0.5Cu alloy, such cracks are not observed, and ordinary creep deformation occurs in the solution. The effect of sustained applied stress, i.e., creep, on the dissolution of ions is smaller for Sn-0.5Cu alloy than for Sn-3.0Ag alloy. The present results suggest that there are differences in the susceptibility to cracking under applied stress in a solution, i.e., creep corrosion cracking, among lead-free solder alloys. (C) 2014 Elsevier Ltd. All rights reserved.

  DOI

• Risk Based Maintenance (RBM) Toward Risk Based Corrosion Engineering

  Jun’ichi Sakai

  Corrosion Engineering   63 ( 4 ) 116 - 125  2014

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Awards 【 display / non-display 】

Awards 【 display / non-display 】

• 腐食防食学会 技術賞

  2014  

• 腐食防食協会 技術賞

  2008  

• 腐食防食協会 協会賞

  2008  

• 腐食防食協会 岡本剛記念講演者

  2006  

Research Projects 【 display / non-display 】

Research Projects 【 display / non-display 】

• 電子材料の腐食

• リスクベース保全技術

• 高温損傷

• Tiの耐環境特性

• 生体材料・口腔材料

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Presentations 【 display / non-display 】

Presentations 【 display / non-display 】

• ステンレス鋼の耐発銹性に及ぼす不働態皮膜の安定度の影響

  腐食防食学会 関東支部技術交流会 

  Presentation date： 2015

• カソード水素チャージによる純Zrの表層剥離発生挙動の解明

  腐食防食学会 関東支部技術交流会 

  Presentation date： 2015

• 硫黄蒸気環境の銀の硫化挙動におよぼす風速の影響

  日本金属学会 2015年 春期講演大会 

  Presentation date： 2015

• 水素化物の析出形態を変化させた純Tiの変形組織観察

  日本金属学会 2015年 春期講演大会 

  Presentation date： 2015

• ステンレス鋼の耐発銹性に及ぼす塩化物による不働態皮膜の破壊の影響

  日本鉄鋼協会 第169回春季講演大会 

  Presentation date： 2015

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Specific Research 【 display / non-display 】

Specific Research 【 display / non-display 】

• 耐食材料の電気化学的評価に関する予備的調査研究

  2000  

  　View Summary

  　Ni-Ti超弾性合金は優れた耐食性、生体適合性を有しており、医療分野でも利用される機会が多くなっている。しかし、生体内環境や、口腔内環境は金属材料にとって苛酷な環境であり、損傷事例も報告されている。歯科矯正用ワイヤーも期待寿命より短期間で破損している。このような現象を例に予備調査を進めた。Ti合金は環境因子の感受性が高いが、口腔内での腐食現象に影響を与える環境因子は十分には解明されていない。環境因子として腐食現象の結果として生体液から発生し、合金内に侵入する水素イオンに着目し、その材質劣化への影響を検討した。Ni-Tiワイヤーに応力負荷条件下で水素イオンを陰極チャージし、材料履歴とチャージ量とを因子として水素脆性感受性を調査した。水素添加定荷重試験において破断までの時間はマルテンサイト変態誘起応力に依存する事が明らかとなった。応力誘起変態後は環境因子の影響を受けやすく材質の劣化が促進される事が考えられる。超弾性特性に着目した材質的変化と環境因子との相関に着目した研究を進める必要があろう。

Committee Memberships 【 display / non-display 】

Committee Memberships 【 display / non-display 】

• 2009

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  （公社）腐食防食学会  会長

• 2004

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  （公社）日本鋳造工学会  評議員

• 2003

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  （公社）日本金属学会  評議員