2004 Fiscal Year Final Research Report Summary
Study on the double-layrs structure of electnodeposits on the marine steel structures catbodicay probed in seawater
| Project/Area Number |
15360457
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Naval and maritime engineering
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| Research Institution | Hokkaido University |
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Principal Investigator |
KASHIKI Isamu Hokkaido University, Graduate School of Fisheries Sciences, Associate Professor, 大学院・水産科学研究科, 助教授 (60001624)
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| Co-Investigator(Kenkyū-buntansha) |
AKAMINE Kenichi IHI Co., Ltd., Production Engineering Center, Chief of a section, 生産技術開発センター材料加工グループ, 課長(研究職)
SUZUKI Akira Hokkaido University, Graduate School of Fisheries Sciences, Professor, 大学院・水産科学研究科, 教授 (90002089)
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| Project Period (FY) |
2003 – 2004
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| Keywords | steel / seawater / cathodic protection / calcareous deposit / magnesium hydroxide / calcium carbonate / double layers / electrophoresis |
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| Research Abstract |
Recently, there is an increasing trend of utilizing oceanic space for some activities of human being. This trend makes various kinds of structures be necessary to be constructed in seawater. In accordance with this, the maintenance of these marine structures has become important, particularly because oceanic environments are far more severe in maintaining structures than terrestrial ones. A method of maintaining ferrous marine structures is a cathodic protection (CP) accompanied with calcareous deposits. Previously, we revealed that the calcareous film deposited on a marine structure is composed of double layers of Mg(OH)_2 and CaCO_3 with a clear boundary between the two. The objective of this study is to propose a simple method of analyzing the respective structures of the double layers, i.e., Mg-and Ca-rich layers, separately, and to examine the validity of the method. Needless to say, it is very important to know the structure of calcareous deposits, because the calcareous deposits play a main part in the cathodic protection of a marine structure accompanied with a deposit.
In this study, a new method was proposed of analyzing the double layrs structures of calcareous deposit films formed on the surface of steel cathodically polarized in seawater. The method was based on the assumption that pore-water in the deposits should be distributed between the layrs according to the difference of their water-affinities. From the assumption, various structural factors concerning the double layers in the deposits were derived. In order to examine the validity of the theoretical model for analyzing the double layers structures, calcareous deposit films with various Ca/Mg compositions was prepared through either varying hydrodynamic state of seawater around the cathode or diluting seawater under a constant cathodic current density and temperature. The application of the above model to these deposits proved the validity of the model to analyze the double layrs structures.
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