What is meant by cathodic protection?
(a) Steel is coated with a layer of paint.
(b) Iron in steel is oxidized to form a protective oxide coating.
(c) Steel is coated with zinc because zinc is more easily oxidized than iron.
(d) A strip of magnesium is attached to steel because the magnesium is more easily oxidized than iron.

Question

What is meant by cathodic protection? 
(a) Steel is coated with a layer of paint.
(b) Iron in steel is oxidized to form a protective oxide coating.
(c) Steel is coated with zinc because zinc is more easily oxidized than iron.
(d) A strip of magnesium is attached to steel because the magnesium is more easily oxidized than iron.

Accepted Answer

Hello. In this problem we are asked which is the following best describes cathartic protection. So cathartic protection means that we have two metals that are connected and so one of them serves as what we call a sacrificial anodes and that means that it will get oxidized preferentially to the other metal. So if we look at the standard reduction potentials for iron and magnesium, So the reduction of iron to two iron, then standard reduction potential Is negative 0.44V and for magnesium brian is being reduced for magnesium metal. The standard reduction potential, which we can find in tables generally independence of textbook to point 356V. So this then says that iron with the smaller and less negative standard reduction potential is going to be more likely to be produced. And that means then that magnesium is gonna be more likely oxidized. And so magnesium for example, could serve them as a sacrificial anodes and this would be our iron metal that then would be preferentially reduced so electrons would be passed to the fire metal which should then maintain it being in the reduced state rather than um forming iron ions. So if we look at the answers that have been provided, he says, then steel is coated with magnesium. Magnesium is more easily oxidized and protects the steel from resting. So magnesium is more easily oxidized but it is not coded by magnesium. So that's incorrect. It's just connected to um the steel, it's not coating the steel. The next one then CB says steel is covered with lustrous paint. So we're not talking about painting metal in this case, so that's incorrect. The next one says steel is connected to a metal, like magnesium is more easily oxidized, which protects the steel from rusting. So that is our correct answer. D says iron oxide is added as a thin layer in steel, so that is not athletic protection. And the next one says multi metals like tin and zinc are more easily oxidized than iron and used to coat steel. Again, it says coat and so we're not cutting anything so that again eliminates E. So the correct answer in this case is C. Thanks for watching. Hope this helped.

Verified Solution

Key Concepts

Cathodic Protection

Sacrificial Anodes

Oxidation and Reduction