Advanced Chemistry Projects - Corrosion

Corrosion is the process wherein a metal is oxidized by loss of electrons to more electronegative elements like oxygen, sulfur etc. With the formation of metal sulfides and oxides. Corrosion of iron occurs primarily in the presence of moisture and oxygen. It is an electrochemical phenomena where iron acts as an anode and oxygen as cathode.

Oxidation: Fe(s)-Fe2+(aq) + 2e-
Reduction : O2(g) + 4H+(aq) + 4e-2H2O (l)
Atmospheric oxidation-
2Fe2+(aq)+2H2O(l) +1/2 O2(g) Fe2O3(s)+ 4H+(aq)

In the process of corrosion, iron gets oxidized to ferric oxide. Hence an informative study would entail, tracking the consumption of oxygen. Weigh a known amount of iron filings or iron wire and place it in a netted bag. Place this in a measuring cylinder. In a beaker containing a known volume of water invert a measuring cylinder containing one third the volume of water. The height of the water in the empty measuring cylinder rises till the point where there is air trapped. Note this volume of air. Similarly, placing the netted bag containing iron filings in the measuring cylinder, filled one third with water and invert it into a beaker containing the same volume of water.

Note the volume of air trapped. As rust begins to form and oxygen is utilized the water level in the measuring cylinder rises. The process of rusting may take a maximum of three to four days at 30oC.

The experiment at the K-11 or K-12 grade can be made more quantitative by calculating the amount of oxygen that has combined with the iron filings. The rust formed is weighed. From the weight of the iron oxide formed, the amount of oxygen that has stoichiometrically combined with the given amount of iron filings can be determined.

From the volume change of the water level, the amount of oxygen utilized can be approximated. Thus the first part of the project on corrosion would throw light on the oxygen consumption in the formation of rust. A further step ahead would be to determine the oxygen consumption and formation of rust under different pH conditions. Similarly, presence of electrolytes that would expedite the formation of rust can also be studied.