3. Iron Corrosion—in generalIron Corrosion—in general  A redox reaction in a makeshift voltaic cell  Processes are separate on metal, but often occur at same areas  Spontaneous process  Electrons move through metal and electrolyte solution is air

4. Iron Corrosion—now in detail  Cracked/dented iron more susceptible to corrosion  Higher energy state---oxidation likely  Oxygen from air oxidizes iron  Occurs at “anodic areas”  Fe (s)  Fe +2 + 2e -  Electrons travel along the iron to “cathodic areas” where reduction occurs  Oxygen is reduced  O 2(g) + 2H 2 O (l) + 4e -  4OH - (aq) **Iron goes through 2 oxidations before “rust” forms.

6. Corrosion ProtectionCorrosion Protection  Multiple ways  2 main ways 1) Galvanized Iron 2) Cathodic Protection

7. Corrosion Protection— Galvanized Iron  Iron coated with more reactive metal (Zn)  Outer layer of zinc placed around iron  Zinc reacts with oxygen in the place of iron  Zinc sacrifices itself—goes through corrosion (Ex. Galvanized iron nails)

8. Corrosion Protection— Cathodic Protection  Iron/steel connected directly or indirectly to an active metal (Mg, Al, or Zn)  Active metal sacrifices itself in place of the iron/steel  “Sacrificial anode”  Iron acts as the cathode and reduction occurs there  Ex. Ships, plumbing, pipes

10.  ENJOY YOUR SPRING BREAK !!!