Every element in the periodic table falls into one category of metals, non-metals or metalloids. Metals are the most common type and they are defined by certain chemical and physical properties. Metals can be narrowed down by looking at their chemical properties. They have positive valences, which means that they give electrons to the atoms they bond with. Giving negative electrons away makes the metals form cations. (BrainPop) As metals form cations, they are able to oxidize and this makes them prone to corroding when exposed to dampness.
Corrosion is the deterioration of materials as a result of a chemical reaction. The most commonly referred to corrosion is the process of rusting. Rusting is harmful as it negatively affects the physical properties of the metals. A corroded piece of iron is not durable, malleable, and will no longer provide functionality. Most metals rust, but the rate at which they corrode is different. Metals like Aluminum seem to resist corrosion, but the metal iron corrodes rapidly. (Nimmo, Bill. PDF) Iron alloys such as steel rust when they come into contact with oxygen and water. Oxygen and water are required for rusting to occur, and when the two are in contact with iron, an oxidation reaction takes place to form rust. The term “oxidation” refers to the gain of oxygen in a substance. The element whose atoms bond with oxygen atoms are said to be oxidized. For example:
magnesium + oxygen → magnesium oxide
2Mg + O2→ 2MgO
In this case, magnesium is said to be oxidized as it has bonded with oxygen to form magnesium oxide. (BBC News. BBC)
“Reduction” on the other hand, is the loss of oxygen in a substance. Many metals can be extracted from their ores using reduction methods. For example, copper oxide can be reduced to form copper if it is reacted with hydrogen:
copper oxide + hydrogen → copper + water
CuO + H2→ Cu + H2O
Oxidation and reduction occur simultaneously, and therefore chemists often use the term oxidation-reduction when referring to this type of reaction. ("Oxidation." HowStuffWorks. ) The chemical process of oxidation-reduction (or redox) occurs at the surface of a metal when the metal is exposed to oxygen, water, or acids. In most redox reactions, oxygen and water are the main oxidizing agents, and this can be seen with the rusting of iron. When iron rusts, the oxygen in the air, and the water from moisture chemically combine with the iron to form a coating of hydrated iron(III) oxide on the surface of the iron. (BBC News. BBC) ("Oxidation." HowStuffWorks. )
iron + water + oxygen → hydrated iron(III) oxide
This picture below, is an experiment conducted by the BBC website. The experiment shows a nail being placed into three test tubes. The first containing air and water, the second containing water and no air, and the third containing air and no water. The experiment proves that rust only occurs when both oxygen and water are present. (BBC News. BBC)
Iron is very widely used for construction...