Abstract: The feasibility of ingot and 35 steel to cathodic protection for copper tube in seawater was analyzed by measuring their free corrosion potentials,working potentials and driving potentials.The minimum protection potential of copper in seawater was defined.The protection effect was tested by simulated experiment of cathodic protection in lab.The results showed that,iron based materials such as ingot and 35 steel had good protective effect for copper tube in seawater,and the weight loss of copper was decreased by more than 90%.The cathodic polarization potential of copper was stable at about- 680mV and more negative than its minimum protection potential.