YES , you can make iron to float , if its shape is such that the water desplaced by it has equal or more than weight of that iron . Many iron ships are there which floats on water.

As you can clearily see in the figure that the shape of iron veseel is such that the weight of water displaced is much more then the weight of iron vessel itself.

EXAMPLE - An iron ship floats because it is shaped such that it will contain air within its hull and therefore the average density of the ship as a whole including cavities and all the air space is less than the water and therefore it floats.