Question

The process of corrosion can be viewed as an electrochemical cell with cathodic reactions such as:

O2+2H2O+4e−⟶4OH− at +1.229 V

H++e−⟶1/2H2(g) at 0 V

M2++2e−⟶M(s)

Where M is a metal. If this is the case, and we assume iron serves as the anode,

Fe0(s)⟶Fe+2(aq)+2e− at −0.447 V

what must be true of the cathode reactions for corrosion to occur?

a. The standard reduction potential of the cathode must be less than 0 V.

b.  The standard reduction potential of the cathode must all be greater than 0 V.

c. The standard reduction potential of the cathode must be greater than 0.447 V.

d.  The standard reduction potential of the cathode must be less than −0.447 V.

Answer 1

1. The given cathode reaction is taken to decide corrosion of the metals in this context of question.
2. For corrosion to occur the anode having higher negative reduction potential value higher the corrosion of the metal as anode by the oxygen.
3. The cathode having higher positive reduction value it will corrode the metals below it in the galvanic series/ simply can be said electro chemical series.
4. For the given instance the cathode reduction potential be better greater than 0 volts
5. since iron has negative 0.447 v as reduction potential value , it can be corroded by electrodes having greater than -0.447 volts i.e towards 0 and above zero.
6. option b is true here.