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炭素鋼さび層の構造と防食性に及ぼすAl³⁺イオンの影響を調査した．Al³⁺イオンの共存によりα-FeOOH構造を主体とするさび層が生成することが明らかとなった．重防食塗料にAl³＋イオンを共存させた反応性塗料を，塩化物イオンを含む残存さび層を有する炭素鋼に適用した場合，β-FeOOHとFe₃O₄構造を主体とした防食性に乏しい残存さび層が，反応性塗料によりα-FeOOH構造を主体とした防食性を示すさび層に変化した．このようなさび構造の変化がない場合は，さび層の防食性は確認できなかった．, Effect of Al ion on the structure and corrosion protection of rust layer on a carbon steel has been examined. It was found that coexistence of Al ion in atmospheric corrosion environment leads to preferential formation of α-FeOOH structure in the rust layer. Addition of Al ion into heavy-duty coating brings the structural change effect to the rust layer; that is, residual rust consisting mainly of β-FeOOH and Fe₃O₄ on salinity-pre-corroded carbon steel can change its structure to α-FeOOH considerably after applying the heavy-duty reactive paint coating. This change in the structure of rust layer results in higher corrosion protection properties of the reactive paint.

含水率5.5 ppm, 30 ppm, 5000 ppmに制御した室温のEMI-TFSIイオン液体中でSUS304とSUS430LXのCVを行った．CV中に変化した皮膜をAESならびにTEM/EELSで解析した．CV後の不働態皮膜は，水溶液中で形成された皮膜と同様に主としてCrおよびFeの酸化物で構成されていた．CVサイクル数の増加に伴い，膜厚と皮膜中のCrカチオン分率が増大した．さらに，EMI-TFSI中の含水率が低いほど，よりCrが濃化し，より薄い皮膜を形成する傾向が認められた．これらの結果から，SUS304とSUS430LXは低含水率のEMI-TFSI中で耐食性を有すると考えられる．, SUS304 and SUS430LX stainless steels were subjected to cyclic voltammetry (CV) in EMI-TFSI ionic liquid containing water of 5.5, 30 and 5000 ppm at room temperature. Structural changes of passive film during CV was characterized by AES and TEM/EELS. Passive films after CV were mainly composed of mainly Cr and Fe oxides similar to that formed in aqueous solutions. The thickness and Cr cation fraction of passive film increased with increasing CV cycles. Furthermore, much Cr concentrated and thinner passive films were formed with less water content in EMI-TFSI. It is concluded that SUS304 and SUS430LX stainless steel are corrosion resistant in EMI-TFSI ionic liquid with small amount of water.

加圧水型原子炉の一次系冷却水を模擬した高温高圧水中にて，冷間加工を加えたAlloy600，Alloy690に生成する不働態皮膜を光電気化学応答によって評価した．一部の試料について放射光をX線源とする光電子分光法による表面分析を実施した．Alloy600とAlloy690に生成する不働態皮膜は，バンドギャップ3.5 eVのp型半導体としての性質を示す酸化物層と2.3 eVのn型半導体的性質を示す水酸化物層から構成されていることが分かった．しかし，酸化物層中には，一般にp型半導体としての性質を示すNi酸化物はほとんど含まれていなかった．一方，皮膜生成時の溶存水素とこれら合金に対する冷間加工の影響はAlloy600で顕著に現れたがAlloy690ではほとんど見られなかった．すなわち，Alloy600に生成する不働態皮膜は溶存水素により薄くなる．また，冷間加工によってやや厚くなり，保護性が低下することが明らかとなった．, Passive films formed on Alloy 600 and Alloy 690 in the simulated primary water of pressurized water reactor were characterized by photo electrochemical current response focusing on the influence of the dissolved hydrogen and cold working. Some specimens were also analyzed by X-ray photoelectron spectroscopy using the hard X-ray generated by SPring-8. Passive films on both alloys consisted of the oxide layer of p-type semiconductor properties with band gap energy (Eb) of 3.5 eV and the hydroxide layer of n-type semiconductor with Eb of 2.3 eV. However, the content of Ni in the oxide layer which may induce p-type semiconductor property is negligible small. The passive films on Alloy 600 become thinner by dissolved hydrogen, and less protective by cold working. Whereas passive films on Alloy 690, which were more protective than that on Alloy 600, were rarely influenced by cold working and dissolved hydrogen.

解説特集, ロータス型ポーラス金属は医療材料としての応用など様々な特徴を有している．加圧した水素，窒素等の雰囲気中で，溶融金属を一方向凝固すると，一方向に伸長した気孔を含むインゴットが得られる．このプロセスによって金属材料を機械的特性を損なうことなく軽量化できる．本稿では，腐食挙動や生体親和性などのロータス型ポーラス・ステンレス鋼の特徴を著者らの研究成果に基づき解説する．, Lotus type porous metals and alloys have various properties including advantages to be applied bio-medical use. Ingot with randomly distributed directionally elongated pores is able to be produced by unidirectional solidification in a pressurized gas atmosphere such as hydrogen and nitrogen. This material exhibits apparently low density without loss of mechanical properties. In this review, corrosion behavior and bio-compatibility of lotus-type porous austenitic stainless steels are described based on the authors' experimental results.

SUS304ステンレス鋼に各種塩の希薄水溶液を塗布した試料を大気環境を模擬した相対湿度90％，60℃の恒温恒湿環境に保持し，不働態皮膜を光電子分光法にて解析した．不働態皮膜の厚さとCr濃度は微量塩類の影響を受けた．この環境中で，ステンレス鋼表面に生成する水薄膜の厚さは塗布した塩の飽和溶液の平衡相対湿度に対応して変化するとみられる．すなわち低い平衡相対湿度の塩を塗布した試料ほど厚い水膜を生成し，その結果Feの選択溶解が進行し，よりCr分率の大きな不働態皮膜を形成する．塩化物はCr濃縮を促進するが，高濃度となると局部腐食を発生した．塩化物を塗布した場合，生成する不働態皮膜は条件次第では高い耐局部腐食性を示すことがあった．硫酸塩もFeの選択溶解を促進するが局部腐食を生じることはなく，不働態皮膜は安定に成長した．, Passive films formed on SUS304 stainless steel that were covered with thin water layer containing various kinds of salt and exposed to atmospheric corrosion environment of 90％ relative humidity and 60℃ were characterized using X-ray photoelectron spectroscopy (XPS). Thickness and Cr content of passive films were affected by a minute amount of salts provided on the surface as a thin water layer. Thickness of the thin water layer on the surface of the steel seemed to be controlled by the equilibrium relative humidity of saturated solution of chlorides supplied on the specimen. Namely, the thickness of the thin water layer containing chloride with low equilibrium relative humidity was larger compared to that containing the chloride with higher equilibrium relative humidity. As a result, the selective dissolution of Fe is stimulated under the thicker water layer to be the more Cr containing passive films. Chlorides enhanced the formation of more Cr enriched passive films, but more concentrated chloride caused localized corrosion. In particular, passive films formed with the thin water layer containing suitable amount of sodium chloride occasionally exhibited high localized corrosion resistance. Sulfates also accelerated the selective dissolution of Fe and increased Cr content in passive films, resulting in stable growth of passive film without localized corrosion.