Casestudy: MIC in an industrial water distribution system
The main aim of this project was to assess the occurrence of MIC in an industrial water distribution system that struggled with leakages on a regular basis. Note that several industrial water distribution systems involve old mild steel pipeline infrastructure that, even in the best of cases, is only externally coated or cathodically protected. MIC is a rapid form of highly localized corrosion. Due to the complexity of the phenomena involved in MIC, many cases are ignored or misdiagnosed. Most cases are linked to the distributed water and are therefore related to internal corrosion, which is only detected once leakages appear. Diagnosis of MIC must follow a case-by-case approach.
Failure analyses revealed clearly that the main cause of failure was internal corrosion in the form of homogeneous pitting. Pits penetrating the pipe wall were consistently located under tubercles several cm across. SEM/EDX showed sulfur localized in specific, layered areas within the corrosion products. Typical corrosive microbial products were found associated with corrosion products and an active biofilm community dominated by sulfate-reducing bacteria was in close proximity to perforations.
Due to the presence of surface-bound biofilms, which can be covered by massive corrosion products, Endures recommended that a biocide with a relatively long residual time in the distribution system be used. The exact dosing of this biocide was carefully implemented. A reliable monitoring system was developed in order to avoid extra corrosion problems due to the biocide itself.
Careful analysis reveals the cause of corrosion-related problems and provides answers for a sustainable solution or future improvements.