Why aluminium hulls offer little to treaty-era warships

How useful would aluminium hulls be for treaty-era warships if the metallurgy were adequate?

The benefit would be limited, with a steel hull and selected aluminium sections more plausible than an all-aluminium warship.

An aluminium hull would reduce structural weight, but a treaty-era warship would still have to carry heavy weapons and equipment. The answer therefore does not treat an all-aluminium hull as especially useful even if metallurgy could meet the basic demand. A more plausible arrangement would retain a steel hull and use aluminium only in selected sections. The material change cannot remove the weight and strength requirements imposed by the ship's combat load.