2. 7. Determination of anode efficiency
The anode efficiency was determined at two current densities,
namely: 25 and 90 mA/cm 2 for the pure-zinc electrode;
25 and 120 mA/cm 2 for the alloy (Zn + 0.01 wt.% Mg + 0.01
wt.% Pb) electrode. The electrolytes were: (i) 10 M NaOH,
and (ii) 10 M NaOH with 15 wt.% sodium citrate. The
cathode was a cylindrical platinum electrode with a very high
surface area. The experiments were conducted for 1 and 2 h.
The working electrode (anode) and platinum cathode were
immersed in 250 ml of the test solution. The latter was stirred
well by means of a magnetic stirrer throughout the experiment.
At the end of the experiment, the working electrode
was removed, cleaned in chromic acid as before, washed and
dried. The weight loss was determined after correcting for
the blank loss. The anode efficiency was calculated using the
relation: