Corrosion Mechanism and Corrosion Factors

Abstract

First of all, we have to define the term “corrosion” in an interesting way.When you observe the rust spots on a car, the question is why was the rust formed? It was formed because of the reaction between iron and the environment. This may be the atmosphere, water, soil, chemicals, etc. We call rust a “corrosion product” formed on iron surfaces.

Can we always observe a corrosion product (substance, for example, rust) as a result of a reaction between a metal and its environment? No! Sometimes you observe pits in a metal surface, but you do not see the corrosion product in the pits (Figure 1.1).

Why were the pits formed? They were formed as a result of the reaction between a metal and the environment, but we do not see the corrosion product.

Another example – cracks in a tube (Figure 1.2).We do not observe the corrosion product as a substance in the cracks or in the vicinity of the cracks. Why were they formed? They were formed as a result of a reaction between a metal and its environment.