Real time imaging of thin water layer formation using polarization camera

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K18797
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 26:Materials engineering and related fields
• Research Institution: Hokkaido University
• Principal Investigator: Fushimi Koji 北海道大学, 工学研究院, 准教授 (20271645)
• Project Period (FY): 2021-07-09 – 2023-03-31
• Keywords: 偏光 / エリプソメトリー / イメージング / その場観察

Outline of Final Research Achievements

An imaging ellipsometry that rapidly derives an optical factor image of the sample interfacial structure from the polarization state image of reflected polarized light was developed using a polarization camera. In-situ observation of the formation of water layer by the deliquescence of NaCl particles as a precursor process of atmospheric corrosion was successfully demonstrated. The anodic polarization behavior of the Fe-6Cr surface in Na2SO4 aqueous solution was captured in a movie that depended on the substrate metal microstructure. By converting the obtained polarization state images into optical factor images, it was shown that the changes in the interfacial structure during the transient states of pre-passivation of Cr components in the first half of the active state, formation of a thick salt layer in the second half of the active state, and passivation are functions of the refractive index of the solution or the thickness distribution and time of the salt film and oxide film.

Free Research Field

腐食防食

Academic Significance and Societal Importance of the Research Achievements

金属試料表面に形成する薄膜の物性（光学定数や膜厚）分布をその場動画撮影可能にするイメージングエリプソメトリーの開発に成功した。大気環境における塩微粒子の潮解を要因とする水（溶液）薄膜の形成過程はもとより合金の活性溶解および不働態皮膜の形成過程のその場観察を可能にする本装置を適用することにより、さまざまな金属材料の腐食機構や速度論の解明が進展し、従来より正確な腐食余寿命の予測が可能になるものと期待される。