A study of the mechanisms involved in corrosion produced by micro-organisms within fuel systems

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McEvoy, J., 1985. A study of the mechanisms involved in corrosion produced by micro-organisms within fuel systems. PhD, Nottingham Trent University.

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Abstract

Fuel tank sludge yielded bacterial, yeast and fungal isolates; several were partially identified. The growth characteristics of mixed and pure cultures, especially Cladosporium resinae, were examined. The corrosion effect of C. resinae was described for stainless steel, mild steel, cupronickel and aluminium alloys in modified sea water or Turner's solution with n-undecane. Growth was assessed by dry weight and subsequent pH, acid content, redox and corrosion potentials in the aqueous environment. Corrosion was assessed by weight loss, pit depths and microscopic appearance. Corrosion rates of the culture filtrates were also determined electrochemically. A laboratory mixed culture and particularly a sludge sample were more corrosive than C. resinae, though the organisms, the metal and the environment all interacted with each other and collectively affected the result. In addition the relative corrosivity was dependant on the exposure time.

Corrosion was more severe below adherent growth; pits, channels, blisters or intergranular corrosion being dependant on the metal under test. In the presence of C. resinae weight loss was generally found to be more severe in Turner's solution than in modified sea water, the losses being up to nine times greater than in the control. Using the linear polarisation technique corrosion rates were continuously monitored in and below the interfacial growth of C. resinae and this showed that both a modified environment and particularly adherent growth enhanced corrosion.

Several organic acids produced by C. resinae were corrosive to the four metal alloys, this seeming to depend on the anion rather than the subsequent pH. C. resinae sequestrated several metal ions, whose presence showed variable inhibition of germination, growth and adherence, and modified acid production and enzyme activity of the fungus.

C. resinae exerted a corrosive effect which depended on the metal, the environment, adherence and exposure time. The action of differential aeration cells, localised concentration of corrosive products and selective removal of metal ions probably played a role in corrosion by C. resinae.

Item Type:

Thesis

Creators:

McEvoy, J.

Date:

1985

ISBN:

9781369325799

Identifiers: