Alloy specimens were prepared either by alloying four nine grade Al with four nine grade Mg or by alloying commercial grade Al with Mg, the composition of the first series being 2.5-5.5% of Mg, and of the second series 52S, ANP and 56S.
The corrosion resistance was tested with a specimen immersed in 1N HCl by measuring the amount of evolved H per unit surface area and per unit time.
The results obtained were as follows:
When Al-Mg alloys, super-saturated with Mg are aged at 65°C for a long period (1-3.5yr), their corrosion resistance rapidly decreases and the grain boundaries are selectively corroded. Such a variation in corrosion resistance property is accelerated if cold working is added on the super-saturated alloys and then aged.

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As clearly stated in the previous notes, the adding of silver has proven to be the most important factor in improving the anti-corrosive quality of lead. However, this involves two problems: 1) silver is relatively costly, 2) how should we determine the quantity to be added to the lead?
This time, I conducted the experiment only from the corrosion point of view, aside from this economical problem. And, I was able to obtain some favorable results on the determination of adding amount of silver.
The corrosion test was performed in artificial sea-water at constant current density. The results obtained were as follows:
1) The most suitable addition of silver to obtain the best anti-corrosive quality is from 3.0% to 4.5% in range.
2) When its addition is 1% or less, anodic corrosion advances so that it no more keeps an anti-corrosive property.
3) The addition more than 4.5% will not improve its anti-corrosive quality when performed in 3.0%-4.5% solution.
4) The temperature of solution does not affect the adding amount of silver, i. e., 3.0%-4.5%.
5) The stirring, also, does not change the adding amount of silver, to get the best possible results.

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The reason why the Pb-Ag alloy, as an anti-corrosive electrode, is proved to be excellent, is that the alloy forms a precise and sturdy film on its surface in the corrosive solution, i. e., the artificial sea-water.
And as observed in other electrodes composed of different material, this surface is also greatly affected by the electric current density.
So, the experiment was conducted to find out how the said Pb-Ag, Pb-Ag-Sn, Pb-Ag-Sb anodes react with various current densities.
The results obtained are as follows:
1) At the current density of 0.3A/dm², it did not form a precise and anti-corrosive film. Corrosion amount was increased in proportion with the time spent in experiment.
2) At 1A/dm², the most stable film had been obtained.
3) At the current density of 10A/dm², or less, Pb-Ag anode as well as that containing other component alloys was proved to be quite useful.
4) At the current density of 1-4A/dm², Pb-Ag-Sn anode was proved to be quite useful.
5) At the current density of 1-8A/dm², Pb-Ag-Sb anode was proved to be quite useful.

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