TITLE:
Effects of Zinc Addition on the Performance of Aluminium as Sacrificial Anode in Seawater
AUTHORS:
A. Muazu, S. A. Yaro
KEYWORDS:
Sacrificial anode, anode efficiency, protection efficiency, polarized potential, andanode mass requirement.
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.10 No.2,
February
20,
2011
ABSTRACT: In this work, the effect of zinc addition on the performance of aluminium-based sacrificial anode
in seawater was investigated. The parameters used in assessing the performance of the cast
anodes are anodic efficiency, protection efficiency and polarized potential. The percentages of
Zn in the anodes were varied from 1 to 8%Zn. The alloys produced were tested as sacrificial
anode for the protection of mild steel in seawater at room temperature. Current efficiency as
high as 86.69% was achieved at 6%Zn in the alloys. The polarized potential obtained for the
couples(steel/Al based alloys) are as given in the pourbaix diagrams with the steel lying within
the immunity region/cathodic region ( S-0.5V SHE) and the sacrificial anodes within the
anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th
week were measured. Protection efficiency values as high as 99.26% and 99.13% were achieved
after the 7th and 8th with Al-6%Zn. The microstructure showed the intermetallic structures of
β-phase which breakdown the alumina passive film and thus enhancing the anode efficiency.