Attack by Organisms Other than SRB

Ammonia and amines may be obtained by microbial decomposition of organic matter under aerobic and anaerobic conditions. These eompounds are oxidized to nitrite by aerobic bacteria such as Nitrobacter. Nitrobacter destroys the corrosion inhibition properties of nitrite-based corrosion inhibitors by oxidation in the absence of a biocidal agent in the formulation. The release of ammonia at the surfaces of heat exchanger tubes has a detrimental effect (50). 

Thiobacillus oxidizes inorganic sulfur compounds such as sulfides to sulfuric acid. 

Some Thiobacilli leach metal sulfide ores as follows  

It is useful to note that it is necessary to have oxygen and reduced sulfur for Thiobacilli to act on and produce sulfuric acid. The growth of anaerobic sulfate-reducing bacteria in sewage produces H2S, which migrates to the air space at the top of the line, where it is oxidized to sulfuric acid in the water droplets at the crown of the pipe by Thiobacilli. The corrosion problem is because of the dissolution of alkaline mortar by the sulfuric acid produced by the bacterial action, followed by the corrosion of the ductile iron in the sewage pipe (50). 

The influence of microbiological organisms can be the initiation of either general or localized corrosion. This influence is because of the effect of organisms to change variables such as pH, oxidizing power, flow velocity, and concentration of chemical species at the metal/solution interface. 

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