Generally thety will armore around the magazines and engineering spaces. In my day everything above the main deck was that al-yu-minium stuff. Repair 5, my station during GQ and responsible for fires in the engineering spaces mustered on the mess decks. Protected my about 1/4" of aluminum plate. Common knowlegde was that it would just barely slow a .50 cal round down as it passed through and through. Never made lot of sense to any of us. What good were we if the first hit amidships, even a minor one like being raked by .50 cal, took us out?
