Definition - What does Anaerobic Corrosion mean?
Anaerobic corrosion is a type of microbiologically influenced corrosion (MIC) which causes metal deterioration due to the microorganisms' metabolic activity. In this case, the bacteria causing the corrosion do not need oxygen to survive.
One example of anaerobic bacteria is sulphate reducing bacteria (SRB), which are accountable for accelerated corrosion to offshore steel and ships. Manganese and iron oxidizing bacteria are also classified as anaerobic and are typically associated with accelerated pitting on metals like stainless steel.
Corrosionpedia explains Anaerobic Corrosion
Anaerobic corrosion is commonly caused by specific bacteria which are capable of feeding on nutrients as well as elements found in soil and water. For instance, seawater is the major source of one of the most damaging anaerobic species, known as SRB. The biological actions of such microorganisms change the local chemistry of a certain matter or environment, making it more corrosive, especially to metals. Bacteria that is iron oxidizing can bore a hole in 316 stainless steel that is 5 mm thick in just one month.
This phenomenon affects many industries, including:
- Chemical processing - pipelines, stainless steel storage and tanks, flanged joints, etc.
- Nuclear power - brass, stainless steel tanks and piping, aluminum bronze
- Gas and oil - gas and oil handling systems, water flood and mothballed systems
- Underground pipelines - clay soil that is water saturated, source of SRB
- Aviation - fuel tanks, aluminum tanks
- Metallurgy - increased wear due to emulsions and machining oil breakdown
- Shipping and marine - accelerated corrosion on barges and ships
Once anaerobic corrosion has been identified, biological, metallurgical and chemical analysis of soils, metals and water samples are required. This problem can be prevented through frequent mechanical cleaning as well as chemical treatment using biocides to prevent bacterial growth. Dry storage and complete drainage can also help in controlling the occurrence of anaerobic corrosion.