Hey everyone, this question is a bit long so bear with me. It’s from the BMAT 700 book and it’s Q2.191. Also, is this kind of stuff in the IMAT syllabus because I know galvanic cells are not.
The presence of water lead to corrosion of iron bar. To prevent such corrosion, iron bars can be coated with an element such as zinc using electroplating, in a process called galvanisation.
Which of the following statements is correct?
A. During corrosion of an unplated iron bar, water is oxidised. During electroplating, iron acts as anode.
B. During corrosion of an unplated iron bar, oxygen is reduced; during electroplating, zinc acts as cathode.
C. During corrosion of an unplated iron bar, iron is oxdised; during electroplating, zinc is deposited on the anode.
D. During corrosion of an unplated iron bar, iron is reduced; during electroplating, zinc is deposited on the cathode.
The answer is B and the answer key explains galvanisation by saying:
“During the galvanisation process, the zinc coating, being less noble than iron, tends to corrode selectively. Dissolution of this sacrificial coating leaves behind electrons, which concentrate in the iron, making it cathodic and thus inhibiting its dissolution.”
Is this saying that the zinc is oxidized by water instead of the iron and then leaving the electrons it has lost on the iron bar or are the electrons supposed to be in the water as it has been reduced? I’m not very familiar with the process of galvanisation or corrosion so I’d appreciate any explanation! Thanks in advance