Corrosion: The Importance of Oxygen

Location:

Concepts Shown:

corrosion, oxidation and reduction

Equipment:

  1. Two jars of equal size and volume
  2. One jar top
  3. Water
  4. Two pads of steel wool
  5. Form-a-gasket or other sealant
  6. Two labels
  7. One permanent marker
Procedure:

At the beginning of the term prepare the first jar in the following manner. In class, place a pad of steel wool into one of the jars and fill with water. Cover the rim of the jar with sealant and cover. The sealant will insure that the jar is air tight. Write the date the jar was prepared on a label and place it on the jar. Also ask a few students to sign the label, verifying the jar was prepared in class on the date listed. Instruct the class that they will see the jar when corrosion will be taught. Two days before corrosion will be covered, prepare the second jar in class using the same procedure as before, but do not cover the jar. In class, compare both jars. The jars must be prepared in class and signed by students in order to convince the class that these are the original jars.

Science:

In the first jar, corrosion was stopped when the oxygen supply ran out while in the second jar, corrosion is still occurring proving oxygen is needed for corrosion to happen. By looking at the steel wool, it is easy to see the corroded areas. The steel wool will lose its metallic color and rust. The following oxidation-reduction reactions apply to this corrosion system: oxidation: Fe(s) Fe2+(aq) + 2e- -440V reduction: O2 + 2H2O + 4e- 4 OH- -401V ___________________________________________________ 2Fe(s) + 2H2O + O2 2Fe(OH)2 -1.281V The ferrous hydroxide 2Fe(OH)2, is further oxidized to ferric hydroxide by the following equation: 2Fe(OH)2 + 2H2O + 1/2 O2 2Fe(OH)3

References:

Author:
Dave Goodman
Credits:


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