Aluminium is probably the quickest metal to rust ( I've heard it starts almost instantaneously that's why its hard to solder/braze ) so it will react with the brass, I`m hoping that because ali rust is a usually in powder form, and the ali sleeve in my boat is only 10mm long, I`m hoping some WD40 will be enough to free the rod if it does seize itself together. the bore is near perfect to stop water penetration . Less than a 10th of a millimetre all round, which as you say may cause it to seize, but it wont be heat/friction seizure ,there can be literally no heat is generated in the short time of the 1/2 turn the brass rod has to travel , but chemical reaction between the 2 metals is in the lap of the gods.