Corrosion of metals in an oxygenated aqueous environment is an electrochemical phenomenon in which the metal ions go into solution, leaving electrons that combine with oxygen to produce hydroxyl ions. Biocorrosion, microbial corrosion, or microbiologically influenced corrosion is an electrochemical process where the participation of the microorganisms is able to initiate, facilitate, or accelerate the corrosion reaction without changing its electrochemical nature. Average dimensions of bacteria, yeast, and fungi involved in the corrosion processes range in the scale of micrometers. This characteristic allows the microorganisms to colonize inaccessible areas such as the interior of crevices or pits, resisting the fluid shear stress of a liquid circulating over the metal surface. Most mineral media used for culturing microorganisms in the laboratory usually differ from the composition of natural and industrial aqueous environments. Opposite to biodeterioration, the biodegradation is man's utilization of the decaying abilities of organisms to render a waste material more useful or acceptable.