Microbiologically induced corrosion of steel structures in port environment: improving prediction and diagnosis of ALWC (MICSIPE) : final report

This project deals with accelerated low water corrosion (ALWC) on steel structures in the port environment. It aims at improving knowledge of this microbiologically influenced corrosion by studying metabolically active bacterial diversity and at proposing a model for ALWC diagnosis. The first part of this work consists in the multidisciplinary analysis (physics, chemistry, microbiology, corrosion, modelling ...) of corrosion deposits sampled in three European ports. Distinctions could be made between ALWC and NLWC (normal low water corrosion) in terms of physicochemical and microbiological compositions. Diversity of total and active bacterial communities was evaluated by molecular methods applied on corrosion deposits for the first time. Specific species of SRB and SOB were found to create an active sulphur cycle in ALWC corrosion deposits. In a particular case, the presence of photosynthetic micro-organisms in NLWC deposits could have influenced corrosion processes. These results lead to a statistical model for ALWC diagnosis. Accuracy of the proposed positive and negative markers could be improved by the implementation of more data. Laboratory system devices were also developed to assess biotic and abiotic parameters influences. ALWC was simulated on steel specimens and a specific active bacterial species (type SRB) has been highlighted to have a role in ALWC, even at low concentration. This project enables to reinforce that ALWC is microbiologically influenced and is a complex phenomenon. Molecular methods developed during the project as well as laboratory devices and statistical model are promising tools to have a more comprehensive insight of ALWC mechanism and to help for its diagnosis.