Question

2. Corrosion in neutral medium Some item is made of two metals - zink and nickel which are in contact with each other. The item undergoes corrosion process in neutral moisture containing environment. What metal is going to oxidize? What chemical element (depolizer) is going to reduce? Write down redox equations for both processes: for metal: for depolizer: po-0.23 V 3. Protection metal against Corrosion (anodic coating) Opt right anodic coating for Pb from the following metals: Pt, Al, Cu, Hg You are given standard potential values Po=-0.13 V Pt2Pt no=0.96 V p,--1.70 V Cu2+ +2e. Cuo po 0.34 V p,-0.85 V 4. Protection metal against Corrosion (cathodic coating) Opt right cathodic coating for Pb from the following metals: Mn, Cr, Ag You are given standard potential values Po=-0.13 V ф,--1.19 V ф,--0.74 V 0.80 V

Answer 1

2) Ni is going to oxidised as it's reduction potential is less.

Zn is going to reduce.

Oxidation half reaction - Ni ----> Ni²+ + 2e-

Reduction half reaction - Zn²+ + 2e-. ---> Zn

3) For anodic coating (oxidation) on Pb the reduction potential of anodic half should be less that the reduction potential of PB.

So aluminium coating can be done on Pb.

4) For cathodic coating (reduction) on Pb the reduction potential should be greater than reduction potential of Pb.

So silver coating can be done on Pb.