Atmospheric corrosion of carbon steel in cold regions remains insufficiently understood, particularly under winter conditions characterized by low temperatures combined with high airborne sea salt deposition. This gap necessitates a mechanistically based predictive model. This study developed a concise mathematical model based on outdoor exposure tests to describe the atmospheric corrosion of carbon steel in cold regions, with a focus on oxygen transport. Despite the cold climate, the corrosion rates increased in winter owing to increased airborne sea salt levels and the formation of thicker aqueous salt solution layers. The corrosion rate increased proportionally with the fourth root of the solution-layer thickness. Numerical analyses conducted using the finite element method suggest that oxygen transport processes, including dissolution from the gas phase, influence the corrosion behavior under thin NaCl solution layers. The corrosion rates calculated from solution layer thicknesses using weekly, monthly, seasonal, and/or annual averages of airborne sea salt deposition and relative humidity showed good agreement with the measured values. These results demonstrate the applicability of the proposed simplified model for predicting the corrosion lifetime of carbon steel in cold regions, within the assumptions adopted in this study. Corrosion rate of steel increases with increasing solution layer thickness.Corrosion products of carbon steel are identified as gamma-, beta-, and alpha-FeOOH.Oxygen dissolution rate decreases as solution layer becomes thinner.Corrosion depth calculated from weekly to annual data agree with measured values.

著者は，40年以上にわたり，計測システムおよび測定結果の評価法の開発を通して，金属材料の腐食防食に関する研究に従事してきた．また，コロージョンセミナー企画委員会委員長や「腐食コスト調査委員会」委員長などの重要役職を務め，腐食研究の重要性について広く発信してきた．著者のこれまでの研究とその普及活動を振り返り，今後の課題について述べた．

増子教授は画像解析を腐食分野へ真っ先に持ち込んだ研究者の一人である．彼の業績を振り返るとともに，画像解析を応用した研究の発展と現状，および将来展望について解説した．明暗解析やパターン認識，色解析などによって，さびの組成や分布，あるいは水溶液中のpHやイオン濃度の分布が測定できるようになってきている．ハイパースペクトルカメラなどの新しい技術によって，それらの分布をより正確に捉えられる可能性がある．また，コンピュータの性能の向上に伴い，AIの応用が容易になり，色だけでなく表面性状（テクスチャー）なども加味して，人の感覚に頼らない，腐食状況の把握ができるようになろう．

A new methodology to calculate and visualize the amount of airborne sea salt with a 100 in mesh resolution in high definition has been proposed in this study. A transport calculation module for airborne sea salt is implemented to the atmospheric component of the multi-scale atmosphere ocean coupled model. The computational fluid dynamics model (NuWiCC-ST) results that can calculate the generation and transport of sea salt particles are incorporated to the transport calculation. The coupled methodology has been applied to create a corrosion environment map for Choshi City. The reliability of the developed method was confirmed by comparing airborne sea salt data measured using the dry gauze method with the calculated data.

Galvanic type atmospheric corrosion monitoring (ACM) sensors can distinguish wet and dry conditions of a surface by reporting spiked charge when there is an electrolyte film on the sensor. In this study, Fe-Ag type ACM sensor was exposed to monitor time of wetness (TOWACM) on carbon steel and weathering steel coupons at seven test stations in Thailand. Climate parameters were monitored by weather stations. Chloride and sulfur dioxide deposition rates were obtained by dry gauze and lead dioxide cylinder methods, respectively. The objective was to investigate the effects of TOWACM, climate, and aerosols on corrosion rate in Thailand tropical climate under high temperature, high relative humidity, and frequent monsoon-induced rainfalls. Multivariable linear regression model applied on the first-year corrosion rate yielded predictive equations for ( I ) inland areas-as a function of temperature (T) and relative humidity (RH) and (2) coastal areas-as a function of rainfall (RF) with TOWACM or chloride (CI ) deposition rate. The first corrosion map of Thailand was proposed based on the predictive equations for corrosion rates of carbon steel and weathering steel.

本研究では，マルチスケール大気海洋結合モデル（MSSG）の気象コンポーネントに飛来海塩輸送計算モジュールを実装した上で，海塩粒子の生成と輸送を計算できるCFDモデル（NuWiCC-ST）の結果を取り込むことで飛来塩分量の腐食環境を100 mメッシュ解像度で高精細に視覚化できる新たな方法論を確立した．実際に，千葉県銚子市を対象とした腐食環境マップを作成し，ドライガーゼ法による飛来海塩量観測データとMSSGによるシミュレーション結果の比較により開発した手法の信頼性を確認した．

Based on super-aging society in Japan, a welfare pneumatic device to give passive exercise for the temporally injured elderly and disabled has been actively researched and developed. In previous study, based on opinions of Physical Therapist (PT) and Occupational Therapist (OT), a home-based rehabilitation device that could give passive exercise for patients using extension type flexible pneumatic actuators (EFPA), built-in quasi-servo valves and built-in displacement sensors using a wire type linear potentiometer was proposed and tested. However, the device did not have enough force and stiffness to drive shoulders with both arms. In this study, to get enough generated force and stiffness of the device, a parallel arranged EFPA reinforced with circumferential restraint was proposed and tested. The rehabilitation device for shoulder joint using the improved actuator was also proposed and tested. The built-in attitude control system using valves, sensors and an embedded controller was also developed. As a result, it can be confirmed that the device can give passive exercise with larger moving area and enough force and torque to move patient’s shoulder joint.

The role of mill scale on the corrosion behavior of steel rebars in mortar was studied using Hyperbaric-Oxygen Accelerated Corrosion Tests (HOACT) and polarization measurements. Defects of mill scale deteriorated passivity of rebars when mortar and saturated Ca(OH)(2) solution contained chloride. Localized corrosion beneath mill scale with defects was responsible for the acceleration of depassivation. SEM observations and Raman spectroscopy measurements revealed that a Fe3O4 layer initially formed under the mill scale and further corrosion resulted in migration of Fe ions through the defects and formation of a rust layer mainly composed of alpha- and gamma-FeOOH on the mill scale.

Corrosion of reinforcing steel rebar is a main cause for losing the long-term reliability of concrete structures. When the rebar is corroded, the rust induces cracks and detachment of the cover concrete. On the rebars, the mill scale which is a thick oxide film is formed when the rebar is hot rolled. The role of mill scale on corrosion behavior of rebars in concrete has not been clarified, yet. In this study, the corrosion behavior of rebars with mill scale in concrete was studied using a new accelerated corrosion test we developed. Commercial rebars with 19 mm diameter, which have mill scale of several tens of micrometers in thickness, were used in this study. The corrosion behavior of rebars with and without mill scale in mortar was investigated. To remove the mill scale on the rebar surface, electrolytic polishing was carried out. The rebars with or without mill scale were embedded in mortar with 5.5 mm cover thickness and the sample was cured for 28 days. In order to prompt breakdown of passive film on the rebars, 2.06 M NaCl solution was mixed to the mortar. Using these samples, Hyperbaric-oxygen accelerated corrosion test (HOACT) was carried out [1]. In the HOACT, pressurized oxygen gas is supplied to the sample, and the oxygen reduction reaction on the steel surface is enhanced, which leads to the corrosion acceleration of the steel. In this study, the mortar-covered rebar samples were located in a high pressure gas chamber, and pressurized oxygen gas of 0.6 MPa was supplied. The periods of HOACT were 14, 28 and 56 days. After finishing the HOACT, the samples were embedded in resin, and then the cross section of the sample was observed using an optical microscope. The rust composition was analyzed using Raman spectroscopy measurement. The corrosion of the rebar with mill scale was more significant than that without mill scale. In the case of the sample with mill scale after 14-day HOACT, a rust layer was formed between the steel surface and mill scale, whereas no obvious corrosion was observed on the rebar without mill scale. To investigate the effect of the mill scale on the corrosion resistance of the rebar, anodic polarization measurements of the rebars with and without mill scale were carried out in a saturated Ca(OH) 2 solution with Cl - . The pitting potential of the rebar with mill scale was more noble than that of the sample without mill scale. However, when the mill scale was scratched the pitting potential was significantly shifted to the less noble direction and it was below that of the rebar without mill scale. These results show that the mill scale improves the corrosion resistance of the rebar in mortar, whereas the corrosion resistance of the rebar becomes even worth than that of the rebar without mill scale when the mill scale contains defects. After 56-day HOACT of the sample with mill scale, two rust layers were observed above and beneath the mill scale. Raman spectroscopy revealed that the rust layer above the mill scale was mainly composed of a- and g-FeOOH, and the layer just beneath the mill scale was mainly composed of Fe 3 O 4 . The rust formed on the sample with mill scale during 14-day HOACT was monolayer just above the steel surface and it was composed only of Fe 3 O 4 . It is speculated that the Fe 3 O 4 layer grows under the mill scale at the early stage of corrosion of a rebar. [1] K. Doi, S. Hiromoto, H. Katayama and E. Akiyama, Journal of the Electrochemical Society, 165(9), C582-C589 (2018).

カーボンをカソード電極としたFeCセンサを試作し，屋外環境および恒温恒湿環境におけるセンサ出力挙動について調査をおこなった．屋外試験にて，FeCセンサは，FeAgセンサとほぼ同等出力を示すが，暴露開始数日間と降雨期間に出力低下となる．FeCセンサは，そのI-RH曲線が海塩付着量および湿度増加に伴い電流増加を示すことから，FeAgセンサと同様に腐食センサとして機能する．FeAgセンサに対するFeCセンサの出力は，Ws＝10 g/m2，RH＞70％で0.2倍に低下，同WsのRH＜60％で0.5～2倍の同等，また，Ws＝0.01～1 g/m2の全湿度域で0.5～2倍の同等，Ws＝0.001 g/m2では全湿度域で検出限界以下である．人工海水中，FeCセンサのEcorrは，FeAgセンサと同程度の－0.65 Vであるが，Igalは90μAと，FeAgセンサIgalの1/3以下に低下する．C電極は，Ag電極に比べてカソード電流低下，また，EIS解析から，Rct増加とCdl低下が確認される．C電極／液界面における溶存酸素の還元反応において電子授受等に反応抵抗があるものと考えられる．

Quasi-cleavage facets have been detected in the stress corrosion cracking fracture of type 304 and type 316 austenitic stainless steels under an environment containing chloride. Their morphology and crystal orientation were analyzed. In both steels the cold-worked material (CW) showed higher crack propagation rate than annealed one (ST), where the variation of the propagated crystal planes of the CW was higher than that of the ST, and the {111} facet was detected in the CW. Then the CW reveals higher possibilities to choose a low energy crack path rather than the ST. The rearrangement and multiply of {111} dislocation arrays may introduce the {111} transgranular cracking in the CW, and the combining duplex {111} slip operations may result in the {110} facet.

The number of photovoltaic system has increased drastically due mainly to a profitable selling price of electricity for owners set by feed-in tariff. Metal piles are currently used as typical foundation of the system from the viewpoint of high workability and low cost. However, there is a problem that the corrosion rate of metal foundation pile at ground level is faster than that of other part of the pile. In this paper, soil corrosion at shallow layer was investigated by exposure test in soil, chemical analysis of soil and electrochemical analysis. The corrosion rate of metal pile in shallow soil layer was higher than 0.02 mm/year which is commonly recognized as the corrosion rate of metal in soil. The corrosion rate in shallow soil layer mostly increased with decreasing the polarization resistance measured in soil environment. Those investigated results showed that the macro cell corrosion at ground level is thought to be attributed to change of chemical composition caused by land creation and dispersion of manure.

走査型振動電極法（SVET）は，金属電極近傍の腐食電流密度分布を測定するために適用される．本稿では，SVETの基本的な性能およびその応用例について解説する．システムの検出感度や分解能が，試験片－センサ電極間距離，h，振動頻度，f，および試験液の導電率，κ，などの測定条件に影響されるので，それらの条件は，測定対象，腐食速度，アノード／カソード位置などを考慮して決定されなければならない．しかしながら，最近では，画像処理技術や微小信号検出技術の開発が進んでおり，腐食測定に有益な道具として確立されるであろう．

The surface roughness evolution of carbon steel under corrosion was studied through outdoor exposure and constant humidity corrosion tests. The statistical analysis of the roughness parameters, such as the degree of skewness and kurtosis, are the good indicators to anticipate the corrosion stages. The results indicated that the corroded surface evolution could be classified into three stages of corrosion. The first stage showed shallow and sparsely distributed pits on the surface of the steel with a probability density function of negative skewness and a high degree of kurtosis (Ku > 3). The second stage exhibited pits distributed densely and partial overlapping of pits. In the third stage, the overlapping pits entirely covered the metal surface, thereby exhibiting uniform corrosion. Statistical analysis of the corroded surface indicated that the random depth variable of the uniform corrosion follows the normal distribution. The samples exposed to outdoor for one year exhibited the corrosion in the first stage only, while the samples exposed to constant humidity chamber for ten months showed all the three stages of corrosion.

Copper oxide (Cu-oxide) electrodes were produced by the vacuum deposition of pure copper on a stainless steel substrate, followed by oxidation in air between 150 and 550 degrees C. The potentials and durability of the Cu-oxide electrodes under xenon light irradiation were evaluated, and the effects of the microstructure on the electrode performance were discussed. The photocatalytic effect of a p-type semiconductor in a Cu-oxide electrode was confirmed for all treatment temperatures. Electrodes oxidized at 150 degrees C showed a very weak photocatalytic effect because the main phase of the thin film comprised amorphous Cu. The potentials of the electrodes oxidized at 450 and 550 degrees C shifted to more than 230 mV (SCE) after light irradiation but they immediately decreased to 100 mV (SCE) due to the self-corrosion (photo-corrosion) of CuO. The electrodes oxidized at 250 and 350 degrees C retained their photocatalytic activities at irradiation time of more than 24 h. The initial potentials of the electrodes oxidized at 250 and 350 degrees C are 100 mV (SCE) and 280 mV (SCE), respectively. The potential of the electrode oxidized at 250 degrees C increased with time because Cu2O, which was the initial main phase of the electrode, was oxidized to CuO by a surface reaction during irradiation. In the electrode oxidized at 350 degrees C, the photo-excited electrons and the photo-generated holes hardly reacted with the electrode surface by the interactions between the Cu-oxide film and the passive film of stainless steel substrate. The electrode exhibited the best performance in terms of potential and durability during the light irradiation.