What Does Bacterial Anaerobic Corrosion Mean?
Bacterial anaerobic corrosion is a type of bacterial-induced corrosion which involves the oxidation of metals. The microorganisms involved in this mechanism do not require oxygen to live. This type of corrosion can take place on both metal and non-metal materials.
In an anoxic and humid environment, metal corrosion occurs due to the redox reaction that produces molecular hydrogen from ions of hydrogen needing bacteria, unlike anaerobic corrosion that takes place unexpectedly.
Corrosionpedia Explains Bacterial Anaerobic Corrosion
Bacteria that generate hydrogen sulfide could cause sulfide stress cracking (SSC). For instance, acidithiobacillus, which is a type of bacteria, releases sulfuric acid which could cause damage to various industrial structures such as sewer pipes. Moreover, a bacterium called ferrobacillus ferrooxidans can directly turn iron into iron hydroxides and iron oxides.
Without the presence of oxygen, anaerobic bacteria that require sodium chloride at 2.5% concentration can thrive in both salt and fresh water. One example is D. africanus, which is one of the major microorganisms that can trigger the corrosion process.
Anaerobic bacteria layers can be present in inner corrosion deposits while the outer areas are occupied by aerobic microorganisms. Some of these bacteria are capable of utilizing hydrogen that is generated during the process of cathodic corrosion. Moreover, bacterial deposits and colonies can create concentration cells leading to and enhancing the attack of galvanic corrosion.
Bacterial anaerobic corrosion may appear as pits, holes or spots such as in pitting corrosion. This could happen in pipelines of the gas and oil industry. Furthermore, this type of corrosion can be found in cast iron, resulting in graphitic corrosion, leaving the affected matter with low strength.
In order to fight bacterial anaerobic corrosion, several types of corrosion inhibitors may be used, such as those formulated with benzalkonium chloride, which is widely used in the oil industry.