Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers



Last updated: August 13, 2019

What Does Biofilm Mean?

Biofilm is a ubiquitous, substrate-attached microorganism community confined within a self-developed extracellular polymeric matrix that is highly structured and resistant to environmental disturbance.

Bacterial biofilms generally are most problematic in industrial water systems, as they are responsible for the blockage and fouling of heat transfer equipment. Microorganisms can influence corrosion in a variety of ways, like formation of localized differential cells and sulfate reduction.

Biofilm deposits and biofilm with entrapped suspended debris are foulants themselves, but these often lead to the formation of mineral scales as well. Monitoring and controlling biofilms can prevent equipment failures, reduce environmental damage and minimize revenue loss.


Corrosionpedia Explains Biofilm

Biofilms are collections of microorganisms and the extracellular polymers they secrete, attached to either inert or living substrata. Biofilms are capable of colonizing virtually any surface on earth and they are extremely difficult to kill. In industry, biofilms can be found adhering to surfaces in most aqueous environments, such as those of a pipeline wall or the tubes of a heat exchanger.

Nearly every species of microorganism (such as microalgae, bacteria, archaea, fungi) is able to form biofilm via synergistic adherence to surfaces and to each other. Understanding biofilm and mitigating its adverse effects are critical for a wide range of applications, ranging from corrosion prevention to the treatment of infectious diseases.

Biofilm can accelerate the partial reaction rates in corrosion processes and shift the mechanism for corrosion. Biofilms can influence the corrosion of metals by:

  • Consuming oxygen, the cathodic reactant
  • Generating corrosive substances
  • Generating substances that serve as auxiliary cathodic reactants
  • Increasing the mass transport of the corrosion reactants and products, therefore changing the kinetics of the corrosion process

In the oil and gas industry, biofilms interact with molecular hydrogen present on the surfaces of pipes and produce hydrogen sulfide as a byproduct of metabolism. This process breaks down the iron and steel of even heavy-walled pipes, resulting in leaks and catastrophic pipeline failure. Other classes of biofilm can form thick plaques capable of plugging heat exchangers and valve bodies.

Biofilms can be controlled through the use of microbicides, biodispersants and by limiting nutrients. Microbiocides, both oxidizing and nonoxidizing, can be effective in overall biofilm control when applied properly.


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