What Does Absorption Mean?
Absorption is a chemical or physical phenomenon in which the molecules, atoms and ions of the substance getting absorbed enters into the bulk phase (gas, liquid or solid) of the material in which it is taken up. Absorption is the condition in which something gets mixed or absorbed completely in another substance.
Corrosionpedia Explains Absorption
The process of absorption is completely different from adsorption and should not be confused. In the adsorption process a liquid or gas accumulates on a liquid or solid surface and builds an atomic or molecular film. However, in the absorption process, a substance goes through diffusion into a solid or a liquid to produce a solution (i.e., molecules undergoing absorption are taken up by the volume, not by the surface).
In the absorption process, a substance captures and transforms energy, which can cause metals to corrode. Therefore, in acidic environments corrosion of metal takes place because of oxidation and other reductions. The oxidation reactions occur at the anode where the metal loses its electrons to the environment and becomes absorbed in the solution in the form of positive ions to the cathode. Electrons are lost from the anodic area and absorbed into ions at the cathodic area. There is a tendency for metal to corrode at the anodic area because the electrons are released from the anode, and cathodic reactions such as oxygen absorption, electroplating and hydrogen evolution take place which increase the corrosion reactions in harsh acidic or aqueous environments.