Exam Question

### (a) Definition of 'Corrosion' and its Natural Occurrence
**(i) Definition of Corrosion**
Corrosion is a natural electrochemical process that causes the degradation of a metal due to its chemical reaction with the surrounding environment. From a thermodynamic perspective, it is the tendency of refined metals to revert to their more stable, lower-energy natural states, such as oxides, sulfides, or carbonates, which are the forms in which they are found as ores.
The process of extracting a pure metal from its ore requires a significant input of energy. This energy is stored within the refined metal, making it thermodynamically unstable. Corrosion is the spontaneous process through which the metal releases this stored energy, returning to its stable compound state.