Mechanism of corrosion in acidic medium.
An acidic environment refers to an environment having a pH value of less than 7.Acidic environments are more prone to cause corrosion than alkaline and neutral environments.
When an acid reacts with a metal, salt is produced with the evolution of hydrogen gas. The general chemical reaction between an acid and a metal is ,
Acid contains H+ ions and tend to accept electrons. They tend to grab electrons and form hydrogen gas. Metals give up electrons and form metal ions. For example ,
Thus , when we put an iron nail in an acid , the H+ ions resent in the acid grab electrons from the iron. Iron gives up electrons and gets converted into soluble Fe2+ ions and the solid material (nail) gradually disappears. The electochemical reaction (which is the sum of oxidation and reduction reaction) is ,
If the acid used is HCl, then the corrosion product is FeCl2.