Cathode protection refers to techniques that preventing the corrosion of a metal by making that metal a cathode. What is corroded in turn is the “sacrificial anode” that is either attached, plated, or alloyed to the original metal. The sacrificial anode will break down first before the protected metal, because it is made of a material with lower reduction potential (and thus a higher oxidation potential) compared to the protected metal.
Watch Practical Engineering’s video on how cathodic protection works in real life.