A ship has lots of bronze fittings and a steel hull. Sea water is a perfect electrolyte so the bronze fittings would immediately attack the steel hull unless something could be done to either protect the steel or give the bronze something else to attack. The classic way to solve this problem is to attach sacrificial zinc pieces to the hull and let the bronze go after them. Again, looking at the chart, you will note that zinc is found on line three from the top of the chart. In other words the zinc is further away from the bronze than the iron is, so the galvanic action takes place between the zinc and the bronze, rather than between the steel and the bronze.
Zinc paint is used for the same reason in many applications.
You will note that active nickel is located twenty one rows from the top of the chart. Passivated 316 stainless steel is positioned nine rows from the bottom. This means that the stainless steel can attack the nickel in the tungsten carbide causing it to corrode. Many of you have run into this problem already. The temperature and concentration of the electrolyte.