10 The Rusting Of Iron

THE RUSTING OF IRON Introduction There are ninety two elements found in nature. More than 80% of these are known as metals or metallic elements. Metal atoms loose some of their electrons to combine with other elements, in particular with oxygen. This process is called the “oxidation” of a metal. This happens at different rates according to the reactivity of the metal as we have already studied. Atmospheric agents are to blame for the oxidation of metallic structures. We call this weathering of metals “corrosion”. The photographs below show the effects of metal corrosion in iron and copper.

Oxidation of iron and other metals occurs when iron heated on a strong flame but not usually at room temperature. Nevertheless we see that some metals (copper, iron, steel especially) form oxides if kept outdoors. This is due to the action of atmospheric agents other than oxygen favouring this process as told before. Particularly in the case of iron the oxide formed is called “rust” and the chemical change is called “rusting”. The rusting of iron is a complex chemical change; it is not combining with oxygen as when iron is heated, but a series of reactions in which humidity (atmospheric moisture) is as important as air. .Other substances may influence the rusting of iron (e.g. salt). To prevent rusting, sometimes a second more easily corroding metal is attached to iron. The metal will rust instead of it. This process is called sacrificial protection

Aims To determine some factors that affect the rusting of iron. Lab ware Test tubes, stoppers, a test tube rack, glass rod, watch glasses. Procedure 1- Put an iron nail (or some iron wool) in each of four different test tubes. 2- Add one of them with 1 ml of distilled water close with a rubber stopper and keep in a rack till next week. 3- Add a spatula measure of anhydrous calcium chloride to the second one, close with a rubber stopper and keep till next week. 4- Boil some distilled water in a 50 ml beaker for 2 – 3 minutes. Cover it with a watch glass and let it cool down without shaking or moving. 5- Cover the nail (iron wool) in the third test tube with this recently boiled water and add it with 1 ml kerosene to prevent oxygen from dissolving in the water. Close with a rubber stopper and keep it till next week. 6- After a week observe the four test tubes and draw your own conclusions about the factors affecting iron rusting. 7- You can dry and stick the four samples to your report.