Microbially induced corrosion attack (MIC) to a locomotive diesel tank

​ESR Technology was requested to determine the cause of blockages leading to fuel starvation in a locomotive diesel tank.  It was suspected by the train operator that the blockage was being caused by debris or contamination entering the tank.  Sampling was performed at various locations within the tank to allow detailed laboratory analysis and the fuel filter was also removed for analysis.

Environmental Scanning Electron Microscopy (ESEM) along with Energy Dispersive X-ray analysis (EDX) was used to examine the collected samples.  Unlike standard electron microscopes, ESEM allows the examination and analysis of non-conducting or biological samples which may contain organic matter and oils.

A rich content of chlorine, carbon, calcium and sulphur along with iron and oxygen was identified within the samples and elongated filament features were observed.  Such features are typical of microbially induced corrosion (MIC), the filaments are caused by yeast and bacteria growth, and are occasionally observed in diesel tanks; being commonly known as diesel sludge.  The presence of iron and oxygen within the samples indicated that corrosion of the tank had taken place, iron and oxygen being the main components of steel corrosion or rust.  The bacteria present within the sludge excrete organic acids which causes pitting corrosion on the steel surface.

In order to prevent future corrosive attack and hence cause fuel starvation, the tank required relatively abrasive cleaning procedures in order to fully remove all traces of the bacteria formation.  Treatments such as diesel biocide may also be used during operational service in order to prevent further microbial activity.

For more information contact Eirwyn Davies on 01925 843417

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