mercury can dissolve large amounts of aluminium metal, making it dangerous to transport in aluminium containers. the thin layer of oxide on aluminium stops it from amalgamating (making an amalgam with) aluminium, but the oxide coating can be damaged to expose the metal. then the aluminium metal is dissolved and oxidizes to aluminium oxide. the aluminium oxide forms a solid and releases the mercury, which amalgamates more aluminium. this process keeps repeating until a large amount of aluminium is dissolved.