Every explosion is “just” a reaction, admittedly one that progresses very quickly (Boom! Kaboom!). Oxidisation is the word used in chemistry to mean “a reaction with oxygen”. Oxidation reactions are essential because they release energy – respiration is an oxidation reaction, as is burning (combustion) and also corrosion. Respiration is good, burning can be good, and corrosion is rarely good. An example of corrosion is iron (Fe) rusting. When Iron combines with oxygen and water, iron oxide is produced:
4 Fe(s) + 3 O2 (g) + 2 H2O (l) → 2 Fe2O3·H2O
The reactants (Iron, Oxygen, and Water) combine chemically to make saturated (·H2O) iron oxide (Fe2O3). Iron oxide has none of the properties that are desirable in alloys of iron – it has low strength, is friable (crumbly) and completely non conductive. We try and prevent corrosion at all times, because it degrades materials. the two most common ways of preventing corrosion are:
- Painting: The paint provides a protective layer that keeps the water/ oxygen from coming into contact with the iron. This stops the iron from contacting either water or oxygen, thus preventing the corrosion reaction.
- Sacrificial Protection: This works by coating one metal by another. The coating metal must be higher on the activity series than the coated metal. One example of this is coating Iron with Zinc (also called galvanisation). This prevents the coated metal from corroding by causing the more reactive metal to corrode first.
The activity series shows some metals are more active than others – here is a video that shows how reactive (explosive!) some metals can be: