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Corrosion Type Microbiological Corrosion

 
     
   
     
  Informational MIC whitepapers  
     
Understanding the Science of MIC
     
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  Understanding, Detecting, and Preventing Microbiologically Influenced Corrosion  
     
  Microbial Corrosion  
 

Effects of Pollutants and Microorganisms on  the Absorption of Electrolytic Hydrogen in Iron

The objective of this research is to define the conditions under which pollutants, in particular those produced by bacteria such as the sulfide end product of the SRB, affect the amount of hydrogen absorbed by iron/steel during open circuit corrosion and under cathodic polarization conditions. At the same time we will be investigating protective measures including the development of improved inhibitors that will work under occluded conditions as exist during microbiological corrosion and localized corrosion in general

 
 

The Molecular Basis of Humic Acid Reduction and its Role in Microbiologically Influenced Corrosion (MIC)

Based on the experimental values of the corrosion potential and the polarization resistance it was demonstrated that iron respiration can protect steel from corrosion. A new electrochemical model that explains the mechanism of this process has been developed. This mechanism is based on the assumption that iron-reducing biofilms reduce the rates of both the oxygen reduction and the metal dissolution reactions that are involved in the corrosion of iron and mild steel.

 
 

The Role of Marine Bacteria in Stainless Steel Pitting

Flat plate and welded stainless steel coupons (316L, Nitronic 50 an AL6xN) were evaluated for potential microbiologically influenced corrosion in seawater. No pitting was observed in flat plate of welded AL6xN under the exposure condition after one year. Pits were located at welds of Nitronic 50 and 316L stainless steels after six- and eight-week exposures. In all cases, large numbers of bacteria were associated with the corrosion products. No corrosion was located on flat plate coupons of 316L or Nitronic 50

 
 

Spatial Relationships between Marine Bacteria and Localized Corrosion on Steels

The role that bacteria play in producing/influencing anodic and cathodic corrosion reactions has been documented in the literature on microbiologically influenced corrosion (MIC). However, the impact of established anodic and cathodic polarizations on deposition or settlement of bacteria has not been adequately addressed. One of the most serious challenges in diagnosis of MIC is differentiation between biological and abiological processes. Most MIC investigations determine spatial relationships between bacteria and corrosion products using microscopy or microbiological diagnostic kits. Spatial relationships are then interpreted as casual. Results from laboratory and field experiments demonstrate that spatial relationships cannot be interpreted as causal. Anodic reactions/products influence the distribution of marine bacteria on both carbon and stainless steel. The attraction of bacteria to anodic sites does not depend on viability of the organisms or concentration of the electrolyte

 
 

An Overview of Microbiologically Influenced Corrosion in Aircraft

Most documented cases of microbiologically influenced corrosion (MIC) in aircraft are related to fungi. Fungi are dessicant-resistant microorganisms that can remain active down to a relative humidity of 65%. Fungi are on photosynthetic organisms, having a vegetative structure known as a hypha, the outgrowth of a single microscopic reproductive cell or spore. A mass of threadlike hyphae make up a mycelium (Figure 1).' Mycelia are capable of almost indefinite growth in the presence of adequate moisture and nutrients so that fungi often reach macroscopic dimensions. Yeasts are fungi that multiply by forming buds instead of mycelia. Fungi are ubiquitous in atmospheric and aquatic environments where they assimilate organic material and produce organic acids including oxalic, lactic, acetic, and citric. Spores, the nonvegetative dormant stage, can survive long periods of unfavorable growth conditions, e.g., drought and starvation. In the following sections fungal degradation of polymeric materials and fuels used in aircraft will be reviewed.

 
 

An Analysis of Possible Microbiologically Influenced Crevice Corrosion of 316 Stainless Steel in a Seawater Environment.

An analysis was conducted of 316 Stainless Steel components which exhibited an unusual degree of crevice corrosion after exposure to seawater for approximately one year. After conducting research into the possible chemical and microbiological mechanisms for the corrosion, a metallurgical and microscopic examination of the components was performed. Results of these examinations indicated that the corrosion observed was probably the result of an interaction between the Gallionella aerobic iron bacteria and the anaerobic sulfate reducing bacteria Desulfovibrio and Desulfomaculum.