Which of the scenarios below are examples of cathodic protection?

1. Using a brass alloy for boat propellors.
2. Treating exposed steel surfaces with acids such as HF.
3. Using paints with pigments containing Fe²⁺ to coat bridges
4. Attaching the metal to be protected to a power supply, making it an electrode in an electrolytic cell
5. Galvanizing steel by coating it in a thin layer of zinc.