Aluminum is porous and can trap chemicals with in them.
I do not know much of the anti-freeze "leaked" into the tank. It would not take much effort to remove the drain plug and remove what ever amount is in there. I would even suggest using some thing like a turkey baster to squirt some fresh water into drain hole.
Some people do believe the RV anti-freeze is completely toxic free. I do not!
I do not put anti-freeze into the fresh water system. I blow out the lines. I put the RV anti-freeze in the drains and toilet only.