Question

Half reaction E0,(v)
Ni2+(aq) + 2e-  Ni(s) -0.23
Co2+(aq) + 2e-  Co(s) -0.28
Fe2+(aq) + 2e-  Fe(s) -0.41
Cr3+(aq) + 3e-  Cr(s) -0.74
Mn2+(aq) + 2e-  Mn(s) -1.03
Which of the following metals could be used successfully to galvanize steel?

Answer 1

Zn forms a series of layers of alloys with iron and lowers the oxidation rate of iron by a factor of 10 to 100. At least one reason for the protective powers of Zn is because Zn serves as a sacrificial anode; i.e., it is easier to oxidize Zn metal than Fe metal. The potential for Zn^2+ + 2e ==> Zn is -0.763 and Fe^2+ + 2e ==> Fe is about -0.40. Therefore, you want a reduction potential more negative than -0.040. Thus I would go with Mn or Cr assuming that they would form a coating that will cling to the iron base metal.