Abstract
Some properties of Al-Zn alloys as a galvanic anode for cathodic protection were considered. Al-Zn alloys containing 2, 3, 4, 5, 10 and 15wt% Zn were tested. Microscopic structures were observed and electrode potential, corrosion rate and anodic polarisation in 3% NaCl solution were measured. Furthermore, the corrosion rate of Zn was measured when coupled with Al-Zn alloys in the same solution.
The results obtained are summarized as follows:
(1) Electrode potential becomes more negative with ncreasing Zn content, and that of alloys containing more than 5% Zn are -0.95V with respect to the saturated calomel electrode.
(2) Corrosion rate of alloys containing less than 5% Zn are nearly equal to that of pure Al.
(3) Al-Zn alloys accelerate the corrosion of Zn when coupled together in 3% NaCl solution, and the corrosion rate of Zn increases by a few % in comparison with self-corrosion.
(4) Anodic polarisation curve of Al-5% Zn alloy have an inflexion at current density of 11mA/dm2.
