[논문]Investigation on electrochemical performance of Al anode material for marine growth prevention system

Kim, Seong-Jong; Jang, Seok-Ki; Han, Min-Su; Lee, Seung-Jun

doi:10.5916/jkosme.2014.38.8.968

Investigation on electrochemical performance of Al anode material for marine growth prevention system 원문보기

한국마린엔지니어링학회지 = Journal of the Korean Society of Marine Engineering, v.38 no.8, 2014년, pp.968 - 973

Kim, Seong-Jong (Division of Marine Engineering, Mokpo Maritime University) , Jang, Seok-Ki (Division of Marine Engineering, Mokpo Maritime University) , Han, Min-Su (Division of Marine Engineering, Mokpo Maritime University) , Lee, Seung-Jun (Division of Marine Engineering, Mokpo Maritime University)

Abstract ▼ AI-Helper

Aluminum anode of marine growth prevention system for ship is installed in seachest or sea water strainer. The Al anode is connected to a control panel that feeds a current to the anode. The dissolved ions produced by the anode are transferred in sea water, spreads through the sea water pipe system and creates a protective film in the pipelines. Thereby, corrosion in pipeline system significantly is reduced. In application on condition as a steel ship, the big accident can be caused by the corrosion. Accordingly, in this research, we evaluated influence of applied current and flow velocity on electrochemical characteristics of Al anode for marine growth prevention system (MGPS). Based on the results of the erosion-cavitation experiments, cavitation rate increased greatly until 120 min. of the experimental time and decreased a little at the point of 180 min. where pit grew and merging occurred but showed a tendency of steadily increasing consumption rates. Based on the results of the Tafel analysis, compared to static states, corrosion current densities show a rapidly increasing tendency when flow occurred.

주제어

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문제 정의

The corrosion resistance of the piping systems is determined by the passive film formed in the relevant environment and if these film is destroyed, the rates of erosion corrosion will be increased rapidly [4][5]. Therefore, in this study, as a study for preventing damage to the seachest of Al vessels by MGPS, the electrochemical characteristics of Al anodes for MGPS in seawater relative to changes in flow velocities and mutual effects of Al anodes and 5083-H116 Al alloy relative to changes in applied currents.

제안 방법

In this study, the Al anode was used which is the MGPS for corrosion protection. Currents were applied to an Al anode (exposed area: 600 cm²) to measure the potential of 5083-H116 Al alloy with distance for 3,600 sec.
Based on the results of the Tafel analysis, compared to static states, corrosion current densities show a rapidly increasing tendency when flow occurred. This study investigated physical properties and electrochemical characteristics of Al alloy for MGPS due to cavitation and corrosion, respectively. It is common that the presence of cavitation under a corrosive environment induces more damage due to synergistic effect[8] between cavitation erosion and electrochemical corrosion[9].
The experiment cell (1500 × 910 × 450 mm) was made of the 5083-H116 Al alloy considering the size of an actual sea chest. To examine the electrochemical characteristics with flow velocity and its effects on performance, experiments were conducted at four flow velocity variables using static state and an agitator. The electrochemical test specimens were mounted with epoxy to expose the area of 1 cm², and all the specimens were polished with emery paper #2000 before testing, washed with ethanol and distilled water, and then dried.

대상 데이터

The experiment cell (1500 × 910 × 450 mm) was made of the 5083-H116 Al alloy considering the size of an actual sea chest.

성능/효과

That is, 2Al³⁺ + 3O^2- → Al₂O₃ will be formed and the corrosion rates will be temporarily decreased in some cases [7]. In conclusion, although a tendency of rapid increases of corrosion current densities compared to static was shown due to the occurrence of flows, the effect of flow velocity increases was shown to be minor. This is considered to be due to the rotating seawater flow which can reduce the thickness of mass transfer boundary layer and promote the diffusion of Al ions and corrosion products into the solution, resulting in increase of reaction rate.
In 800 RPM and 1100 RPM, the potential rapidly moved toward noble direction at the beginning of immersion and then steadily increased thereafter until the end of the experiment. In conclusion, lower potential was shown when there were flow velocities compared to static states and this is because the thickness of the diffusion layer becomes thinner due to flow velocity. Due to this decrease in the diffusion layer, the metal becomes to be subject to more active states and thus it is considered that corrosion damage will be increased compared to static states.

후속연구

It is common that the presence of cavitation under a corrosive environment induces more damage due to synergistic effect[8] between cavitation erosion and electrochemical corrosion[9]. Therefore, in future work, it is valuable to plan an electrochemical-cavitation combined experiment to further examine the damage mechanism.

참고문헌 (8)

U. J. Lim, H. K. Jeong, K. T. Shim, and H. O. Park, "The effect of flow velocity on corrosion characteristics of A1-brass tube," Proceedings of the Korea Society of Marine Engineering Fall Conference, pp. 147-150, 2003 (in Korean).
H. R. Copson, "Effects of velocity on corrosion," Corrosion, vol. 16, no. 2, pp. 130-136, 1960.
T. Sydberger and U. Lotz, "Relation between mass transfer and corrosion in a turbulent pipe flow," Journal of Electrochemical Society, vol. 129, no. 2, pp. 276-283, 1982.

상세보기
S. R. De Sanchez and D. J. Schiffrin, "The use of high speed rotating disc electrodes for the study of erosion- corrosion of copper base alloys in sea water," Corrosion Science, vol. 28, no. 2, pp. 141-151, 1988.

상세보기
L. L. Shreir, Corrosion Handbook Vol. 1, Newnes-Butter Worths, pp. 3-31, 1979.
S. J. Kim and J. Y. Ko, "Investigation on optimum protection potential of high-strength Al alloy (5456-H116) for application in ships," Journal of The Korea Society of Marine Engineering, vol. 30, no. 1, pp. 157-169, 2006 (in Korean).
S. J. Kim, D. H. Kim, M. H. Lee, K. J. Kim, and K. M. Moon, "A study on the influence of Al alloy sacrificial anode efficiency due to marine environmental variation," Journal of Ocean Engineering and Technology, vol. 9, no. 2, pp. 106-111, 2000.
R. J. K. Wood and S. A. Fry, "The synergistic effect or cavitation erosion and corrosion for copper and Cupro-Nickel in seawater," Journal of Fluids Engineering, vol. 111, no. 3, 271-277, 1989.

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