Naked Science Forum

Non Life Sciences => Technology => Topic started by: scientizscht on 19/12/2018 17:20:35

Title: How does cathodic protection works?
Post by: scientizscht on 19/12/2018 17:20:35

Any strong article on cathodic protection?

What's this concept's applications?

Title: Re: How does cathodic protection works?
Post by: Petrochemicals on 19/12/2018 17:34:10

To rust metals require the exchange of electrons with another substance, oxidisers. This means that the electrically cohesive block of metal passes electrical potential to the reacting atoms, usually on the outside.  Metals have a range of reactive electrical potential, some more than others, ie zinc more reactive than iron which is more reactive than gold. If you have two metals with one requiring less energy to react, electrically connected, the metal which is more reactive is the one that corrodes first. It becomes the cathode which atracts other atoms and oxydises first.

Title: Re: How does cathodic protection works?
Post by: evan_au on 19/12/2018 19:37:28

Cathodic protection is often used on ships: A sacrificial lump of zinc is attached to the hull of a ship, under the waterline. The (replaceable) lump of zinc is slowly dissolved away, while the steel hull of the ship remains intact. Forget to replace the zinc, and the ship's hull will start to rust through.

Another form of cathodic protection is used in the telephone network. A battery in the exchange delivers power to telephone in the home through copper wires. The copper wire is held at -48V, relative to Earth. If it were +48V, any water leaking into the wire would quickly corrode the copper wire.

See: https://en.wikipedia.org/wiki/Cathodic_protection