Corrosion chemistry
Introduction:
Closely related to the chemical activity of the metals is the phenomenon of corrosion, the
chemical attack on a metal by its environment. The most common type of corrosion is due to the action
of the atmosphere in conjunction with water and various substances dissolved in water. Essentially,
corrosion is an electrochemical process and involves the type of electron transfer that is characteristic of
voltaic cells.
In this experiment, the corrosion of iron will be studied. The effect of a more oxidizing metal in
contact with iron enhances the rate of corrosion, while a more reducing metal retards the rate of
corrosion. Simulation of iron corrosion is done using a colorless gelatin as its medium.
Materials and reagents:
Colorless gelatin bars
Zinc metal
Copper wire
Ungalvanized clean iron nail
0.1M K3Fe(CN)6
1.0% phenolphthalein
Pliers and sand paper
Procedure:
Part A. Preparation of the nails.
1. Using a sand paper, polish the nails to remove the coating on the surface.
2. Prepare two beakers with the following contents:
Beaker 1: Nail A = Straight nail
Nail B = Another nail with a 45o bent.
Beaker 2: Nail C = Straight nail with a copper wire twisted around it.
Nail D = Straight nail with a piece of mossy zinc forced through the nail
Part B. Preparation of the gelatin solution.
1.
2.
3.
4.
5.
Boil 250 ml distilled water. When the water is boiling, stir 1/2 bar of colorless gelatin.
Continue stirring until all the gelatin is dispersed into the solution.
While stirring, add 1 ml of 0.1M K3Fe(CN)6 into the solution.
Cool the mixture to 60oC.
Add 1.0 ml 1.0% phenolphthalein and mix the solution.
Part C. Corrosion simulation
1. Make sure that the nail contents of each beaker do not touch each other.
2. Pour the gelatin solution into the beakers. Make sure that the fluid level covers the nail at least
1.0 cm.
3. Observe the changes in the setup towards the end of the lab period.