Paper Title:

An Electrochemical Impedance Spectroscopy Study of Al-Zn and Al-Zn-Sn Alloys in Tropical Seawater

Periodical Key Engineering Materials (Volumes 510 - 511)
Main Theme Advanced Materials XII
Edited by Shaheed Khan, Iftikhar us Salam and Karim Ahmed
Pages 284-292
DOI 10.4028/www.scientific.net/KEM.510-511.284
Citation M.C. Isa et al., 2012, Key Engineering Materials, 510-511, 284
Online since May 2012
Authors M.C. Isa, Abdul Razak Daud, M.Y. Ahmad, M. Daud, S.R. Shamsudin, N. Hassanuddin, M.S. Din Yati, M.M. Muhammad
Keywords Aluminum (Al), Electrochemical Impedance Spectroscopy (EIS), Equivalent Circuit Modelling, Open Circuit Potential (OCP), Oxide Layer
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In this paper, a study on the electrochemical behaviour and electrical properties of Al-Zn and Al-Zn-Sn alloys in tropical seawater using open circuit potential (OCP) measurement and electrochemical impedance spectroscopy (EIS) are reported. The results from both the OCP and EIS tests show that surface activation was observed in the Al-Zn alloy with the addition of 1.34 wt.% Sn which can be manifested by the shift of OCP values towards more electronegative direction. The EIS spectra of Al-Zn alloy exhibits a semicircle loop, while the EIS spectra for the Al-Zn-Sn alloy exhibits a semicircle with a semicircle inductive loop. The change in EIS spectra for Al-Zn-Sn alloy is correlated to the increase of surface activation resulting in a less stable passive layer. Equivalent circuits models were proposed to fit the impedance spectra and the corresponding electrical parameters with optimum values were deduced. The modulus impedance in the low frequency region or polarization resistance, Rpol obtained for the Al-Zn-Sn alloy, Rpol = 2.76 kΩ cm2) is slightly decreased compared to the corresponding value of the Al-Zn alloy, Rpol = 3.97 kΩ cm2), indicating a considerable reduction in the protective capability of the oxide layer on the Al-Zn-Sn alloy. It appears that the heterogeneous oxide film and pores formed on the Al-Zn-Sn alloy play a key role in reducing total resistance to the flow of electron at the alloy-electrolyte interface.