Corrosion

It’s all Redox!

Iron 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

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 O2(g) + 2H2O(l) + 4e- 4OH-

(aq)

**Iron goes through 2 oxidations before “rust” forms.

Corrosion Protection

Multiple ways

2 main ways

1) Galvanized Iron

2) Cathodic Protection

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)

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

ENJOY YOUR SPRING BREAK !!!