General embedded zinc block on the shell of ships Because of the hull is made of steel to build steel point chemical reaction happens in seawater erosion hull liquidity than iron and zinc In seawater zinc reaction before iron zinc could lose electrons are eroded While the iron is not eroded Hull would be protected In zinc as the anode in the reaction of electronic eroded And the iron is protected as the cathode in what's called cathodic protection at the expense of the anode