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Extracellular polymeric substances (EPS) were studied with regard to their potential application as inhibitors of biocorrosion. EPS that have been isolated from biofilms of sulphate-reducing bacteria (SRB) were adsorbed on samples of high alloyed steel (type 1.4301) at different temperatures. The samples were exposed to SRB containing solution and afterwards analysed by fluorescence microscopy (FM). The results show that the EPS form an incomplete layer and lead to a smaller amount of cell adhesion when compared to pure surfaces. The results are discussed with regard to the application of EPS for the prevention of biofilm formation.

Microbially influenced corrosion (MIC) of steel has gained increasing attention in recent years because the damage caused by this process is a significant cost factor for industry. Consequently, inhibition of corrosion and especially the development of corrosion protective films is an important present-day research topic. In this connection, application of microbially produced EPS for mitigating steel corrosion is an innovative idea. However, observations of ”protective” biofilms on metallic surfaces have been previously reported. Their inhibiting effect is generally thought to be caused by oxygen depletion or the formation of passivating layers. In contrast to many conventional corrosion protective methods, EPS or EPS-derived agents would be a cheap and environmentally friendly solution. Extensive research activities are still required, before biofilms or cell-free EPS can be used for corrosion protection on larger scale. In this study, we are developing a novel EPS-based corrosion protection method for unalloyed and corrosion resistant steel in aqueous media, which is based upon the application of microbial metabolic products. EPS of various sulfatereducing bacteria and other microorganisms are investigated for their inhibiting effect. The extent of such inhibition is evaluated in a model test system, in which different steels are subjected to corrosive conditions under sulfate-reducing conditions. To elucidate the protective mechanisms, comparative analyses of the chemical composition of the applied EPS are performed.

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