When a piece of magnesium is connected to an iron pipe, the iron is prevented from corroding. which of the following is the best explanation? magnesium reacts with the ground water to form a protective coat on the iron pipe of mg(oh)2. magnesium atoms replace the iron atoms lost when the iron corrodes. electrons flow from the iron through the wire to the magnesium leaving a protective coating of fe+3 on the pipe. when magnesium corrodes, electrons flow through the wire to the iron pipe, thus preventing the iron atoms from losing electrons. the electric current flowing through the ground from the magnesium to the iron kills the organisms which attack and corrode the pipe.