Electrochemical characterisation of hybrid activators for aluminium sacrificial anodes in natural sea water
Date
2013Author
Mohd Subhi, Din Yati
Mohd Nazree, Derman, Dr.
Mahdi, Che Isa
Mohd Moesli, Mohammad
Hasril, Nain
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This paper reports on the electrochemical behaviour of as-cast Al-Zn-Mg alloys activated by tin (Sn) and ruthenium dioxide (RuO2) in natural sea water. The potential and advantages of Sn and RuO2 as hybrid activators in Al-Zn-Mg alloys will be studied by using direct (DC) and alternating (AC) current electrochemical measurement techniques. The morphology of the alloys' corroded surface was studied using a scanning electron microscope (SEM). This study showed that the addition of 1.5%wt. Sn as an alloying element gave a stable corrosion free process that can be achieved after 2 ks of immersion. The results also showed that RuO2 catalytic coating applied on the surface of Al-Zn-Mg-Sn alloy slightly shifted the values of open circuit potential (OCP) towards a more electropositive direction as compared to Al-Zn-Mg-Sn without RuO2. The morphology of the corroded surface of Al-Zn-Mg-Sn alloy coated with RuO2 showed a more uniform corrosion attack with the formation of porous and fibrous mud-like cracks on the outer layer. This type of corrosion morphology features were believed to facilitate ionic species adsorption and diffusion through corrosion product layer at solution-alloy interface. Electrochemical impedance spectroscopy (EIS) showed that both Sn and RuO2 are capable to activate Al-Zn-Mg-Sn alloy in sea water by modifying the electrical properties of the oxide layer, reducing resistance to polarisation Rp values and thus, activating and accelerating the aluminium alloy dissolution process.
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http://www.myjurnal.my/public/article-view.php?id=74570http://dspace.unimap.edu.my:80/dspace/handle/123456789/34119