1. Biological Corrosion,Underground Corrosion and Corrosion in Water
Group 4
Canan Canlı
Cem Peynirci
Özgür Deniz Hamamcı 1302D006
November 27, Wednesday

2. Microbial Corrosion

3. INDEX What is Microbial Corrosion ?
Organisms that cause Microbial Corrosion
Sulfate-reducing bacteria (SRB)
Industries Affected by Microbial Corrosion
Protection from Microbial Corrosion

4. What is Microbial Corrosion ?
Microbial corrosion, also called bacterial corrosion, bio-corrosion, microbiologically influenced corrosion, or microbially induced corrosion (MIC), is corrosion caused or promoted by microorganisms, usually chemoautotrophs. It can apply to both metals and non-metallic materials.
Microbes can interact in the environment with materials/surfaces in so many ways that make the complexity of the system too high to be evaluated by standard corrosion model predictions. Biofilm* formation is considered as the primary step to start a biocorrosion process, allowing the cells to be in close contact with the surface and creating a microenvironment that can be totally different from the bulk with distinct properties: pH, dissolved oxygen, and the presence of organic and inorganic species.
*A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances The cells within the biofilm produce the EPS components, which are typically a polymeric conglomeration of extracellular polysaccharides, proteins, lipids and DNA.

5. Organisms that cause Microbial Corrosion
Some sulfate-reducing bacteria produce hydrogen sulfide, which can cause sulfide stress cracking. Acidithiobacillus bacteria produce sulfuric acid; Acidothiobacillus thiooxidans frequently damages sewer pipes. Ferrobacillus ferrooxidans directly oxidizes iron to iron oxides and iron hydroxides. In presence of oxygen, aerobic bacteria like Acidithiobacillus thiooxidans, Thiobacillus thioparus, and Thiobacillus concretivorus, all three widely present in the environment, are the common corrosion-causing factors resulting in biogenic sulfide corrosion. Layers of anaerobic bacteria can exist in the inner parts of the corrosion deposits, while the outer parts are inhabited by aerobic bacteria.

6. Some bacteria are able to utilize hydrogen formed during cathodic corrosion processes.
Bacterial colonies and deposits can form concentration cells, causing and enhancing galvanic corrosion.
Bacterial corrosion may appear in form of pitting corrosion, for example in pipelines of the oil and gas industry. Anaerobic corrosion is evident as layers of metal sulfides and hydrogen sulfide smell. On cast iron, a graphitic corrosion selective leaching may be the result, with iron being consumed by the bacteria, leaving graphite matrix with low mechanical strength in place.
Various corrosion inhibitors can be used to combat microbial corrosion. Formulae based on benzalkonium chloride are common in oilfield industry.
Microbial corrosion can also apply to plastics, concrete, and many other materials. Two examples are Nylon-eating bacteria and Plastic-eating bacteria.

8. Sulfate-reducing bacteria (SRB)
Sulfate-reducing bacteria (SRB) is a type of microbiologically induced corrosion. The presence of SRB is commonly found in various attributes of the oil and gas industry places as deep as the wells on an offshore oil plant, all the way into the refineries. SRB can occur in any aqueous environments or soil and is a common problem in oil and gas industry facilities due to the omnipresent nature of microbes and corrosive by-products in the pipelines. The presence of the SRB in the crude oil in the form of microbes uses the sulfate as an electron acceptor to generate corrosive hydrogen sulfide (H2S) as their product. SRB utilizes hydrogen to corrode the metal and depolarizes the metal surface due to the hydrogen sulfide product. The following chemical reactions explain the process of SRB.

9. A base metal, such as iron (Fe) goes into aqueous solution as positively charged cation, Fe2+. As the metal is oxidized under anaerobic condition by the protons of water, H+ ions are reduced to form molecular H2. This can be written in the following ways under acidic and neutral conditions respectively:
Fe + 2 H+ → Fe2+ + H2
Fe + 2 H2O → Fe(OH)2 + H2
Usually, a thin film of molecular hydrogen forms on the metal. Sulfate-reducing bacteria, oxidize the molecular hydrogen to produce hydrogen sulfide ions (HS−) and water:
4 H2 + SO42− → HS− + 3 H2O + OH−
The iron ions partly precipitate to form iron (II) sulfide. A reaction with water also occurs, producing iron hydroxide.
Fe2+ + HS− → FeS + H+
3 Fe H2O → 3 Fe(OH)2 + 6 H+
The net equation comes to:
4 Fe + SO42− + H+ + 3 H2O → FeS + 3 Fe(OH)2 + OH−
This form of corrosion by sulfate-reducing bacteria can, in this way, be far more harmful than anaerobic corrosion.

10. Industries Affected by Microbial Corrosion
Chemical processing industries: stainless steel tanks, pipelines and flanged joints, particularly in welded areas after hydrotesting with natural river or well waters.
Nuclear power generation: carbon and stainless steel piping and tanks; copper-nickel, stainless, brass and aluminum bronze cooling water pipes and tubes, especially during construction, hydrotest, and outage periods.
Onshore and offshore oil and gas industries: mothballed and waterflood systems; oil and gas handling systems, particularly in those environments soured by sulfate reducing bacteria (SRB)-produced sulfides
Underground pipeline industry: water-saturated clay-type soils of near-neutral pH with decaying organic matter and a source of SRB.
Water treatment industry: heat exchangers and piping
Sewage handling and treatment industry: concrete and reinforced concrete structures
Highway maintenance industry: culvert piping
Aviation industry: aluminum integral wing tanks and fuel storage tanks
Metal working industry: increased wear from breakdown of machining oils and emulsions
Marine and shipping industry: accelerated damage to ships and barges
Positive identification of microbiologically influenced corrosion requires chemical, biological and metallurgical analysis of the waters, soils and the metal samples.

11. Protection from Microbial Corrosion
Regular mechanical cleaning if possible
Chemical treatment with biocides to control the population of bacteria
Complete drainage and dry-storage

12. References

13. Stray Current and Soil Corrosion
Until about 35 years ago,underground corrosion was attributed solely to stray electric currents from exterral sources such as d-c power lines and electric railways such current pass through parts of underground structures and then discharge to the earth where conditions are favarable; corrosion occurs at the discharge area.

15. Then the importance of underground corrosion was recognized by Congress in In 10 years of field and labratory studies methods were developed that eliminated stray current electrolysis is a major factor in underground corrosion. Unexpectedly, however these studies also showed that serious corrosion often occured when stray currents were obselt.

17. What's the Underground Corrosion?¿
Buried gas or water supply pipes can suffer severe corrosion which is not detected until an actual leakage occures, by which time considerable damage may be done.

18. Electronic Components
In electronic equipment it's very important that there should be no raised resistance at low current connections. Corrosion products can cause such damage and can also have sufficient conductance to cause short circuit. These resistors form part of a rador installation.

21. Factors That Affect Underground Corrosion
Aeration: Aeration factors are that affect the accress of oxygen and moisture to the metal and thereby affect the corrosion process. Oxygen either from atmosphere source of from oxidizing salts or compounds stimulates corrosion by combining with metal ions to form oxides, hydroxides or salts of metals.

23. Electrolyte: Also chemical reactions can occur with electrolyte that cause underground corrosion. The principal function of soil moisture in underground corrosion is to furnish the electrolyte for carrying the current and thereby proruoting the electrochemical corrosion process.

25. Results: Inhomogeneties of the metal surface
Concentration cell effects due to adhering soil particles or crevices where stagnant conditions may exist
Prosences of chlorides in the soil
Microbiological organisms
Abrasion of the metal surface by soil particles or foreign debris

28. Corrosion in Water

29. What is Corrosion?
The corrosion process is an oxidation/reduction reaction that returns refined or processed metal to their more stable ore state.
Because of it, buildings and bridges can collapse, oil pipelines break, chemical plants leak, and bathrooms flood.
Corrosion is one of the most damaging and costly naturally occurring events seen today.

30. Corrosion Control

31. Water and Corrosion
Corrosive water, also known as “aggressive water,” is water that will dissolve materials it comes in contact with.
Corrosive water can cause nuisance problems, health-related problems, and in some extreme cases, it can lead to holes in metal plumbing systems that may require replacement.
Corrosion also affect water quality.

32. How Corrosion Occurs in Water
The most common form of corrosion is iron oxide. (Rust)
Rust occurs more quickly in saltwater than in pure water.
CO2 also contains oxygen and it reacts with water to form carbonic acid this acid also attacks iron.
Once rusting starts, it continues to corrode the metal.

33. The Potential for Water to be Corrosive
The LSI is a measure of the balance between pH and calcium carbonate (CaCO3)—as the LSI value becomes more negative, the water is increasingly under-saturated with CaCO3 and therefore has a greater corrosion potential.
The PPGC is based on the ratio of chloride to sulfate; the higher the PPGC, the greater the potential for galvanic corrosion of lead in the plumbing system.
The LR is defined as defined as the sum of equivalents of chloride and sulfate divided by equivalents of bicarbonate. The LR indicates the corrosivity of water to iron and steel. 
The RI examines degree of precipitation formation against corrosion is determined.

35. Factors Affect Water Corrosion
Thickness of the pipe (thinner walled pipes are more susceptible to corrosion)
Age of the water system
Stagnation time of the water within pipework
PH, temperature, oxygen and mineral concentrations of the water
Velocity and pressure of water within the pipe
Microbiological outbreak, such as legionella
Presence of sand, sediment and other suspended solids

36. Examining the Factors
Of the dissolved gases, oxygen is most important.
The higher the oxygen content the more corrosive the water.
The higher the mineral content also cause more corrosion.

37. Examining the Factors
As the temperature is increased, the corrosion rate usually is accelerated. However, if one considers a saline water at atmospheric pressure, an increase in temperature will reduce the oxygen solubility.
High water temperature can increase biological rate of growth and chemical corrosion.
Corrosion is an electrochemical reaction, meaning that electrons are transferred. Higher temperatures cause the reaction to speed up, meaning that high water temperatures cause corrosion to occur at an increased rate.

38. Examining the Factors
pH (acidic water) and high pH (alkaline water)- For high alkalinity water - it is possible that a chemical scale may form that would help to protect against corrosion, but if a bacteria becomes established the scale, such as SRB (sulfur reducing bacteria), environment may experience a problem related to Microbiologically Induced Corrosion. (MIC)
Some water contains a lower pH value, lower alkalinity value and a higher concentration of minerals and chemical salts such as aluminum, calcium, magnesium, and potassium. The effects of low pH levels in the water, low alkalinity and the presence of certain minerals in the water cause the water to become corrosive.

39. Corrosion in Salt Water, Fresh Water and DM Water
Demineralized Water is not corrosive.
Current flows more easily in salt water than it does in fresh water.
Since rusting is all about the movement of electrons, iron rusts more quickly in salt water than it does in fresh water.

40. What are the consequences of corrosion?
Consumption of water with elevated levels of toxic metals, such as lead and copper, have been shown to cause both acute and chronic health problems.
Decreased efficiency
Failure of the entire system
Staining and reduced water quality

41. How to Prevent Water Corrosion?
Improve the flow of water by smoothing out irregularities and increasing pipe diameters
Decreasing flow rate to minimise turbulence
Monitoring and changing water PH
Changing the pipe material (in extreme cases)
Identifying corrosion early
Coatings
Electroplating
Non-metallic coatings — plastics, paints, and oils — can also prevent corrosion.
Corrosion Inhibitors
Water treatment systems

42. Conclusion
Active corrosion and its costly side effects are a valid concern.
Changes are likely called for on multiple levels, including design, construction, monitoring, and maintenance. Technology is ever progressing, and with it we find new and improved materials, products, and testing methods at our disposal to help guard against corrosion.
Using the control strategies available offers a proactive approach, which allows for increased public safety, better performance, extended operational lifespan, environmental protection, and long-term cost benefits.

43. References https://www.thoughtco.com/how-rust-works-608461
corrosion/
corrosive-water-lead-copper-aluminum-zinc-and-more