Studies on corrosion protection for metals by extracellular polymeric substances

A. Kuklinski, R. Stadler, M. Grooters, W.Fürbeth, W. Sand

Proceedings EUROCORR 2011


Direct application of cell-free EPS represents a promising new approach for pre-vention of MIC due to biofilm formation by detrimental biofilms. Cell-free EPS-extractsfrom 4 different groups of organisms – Desulfovibriospp., Pseudomonasspp., Lactobacillus fermentumand Rhodococcus opacus– were tested regarding their potential to reduce biofilm formation of  sulfate-reducing D. vulgarison alloyed and non-alloyed steel.Biofilm formation was studied on (partially) EPS-covered surfaces. Biofilms and EPS-layers were visualized by fluorescence and scanning electron microscopy. Cha-racteristics of the EPS-films were studied byEDX and EPMA analysesas well as contact angle measurements. Influence of EPS-extracts on corrosion was assessed by gravimetrical analyses. Colorimetric chemical identified carbohydrates, uronic acids and proteins as main fractions of EPS. After coating, EPS formed inhomogeneous films on the steel surfaces increasing their hydrophobicity. Coatings with EPS from Desulfovibrio vulgaris and D. alaskensis strongly reduced biofilm formation by D. vulgaris over periods of more than three days. Films of EPS from  Lactobacillus fermentum reduced MIC of mild steel by up to 88%. However, all EPS-films demonstrated a poor long-term stability against dissolution; increasing temperature during the coating process only slightly improved stability and homogeneity of the EPS-coatings. Currently, specific substance groups found in EPS are assessed for their ability to influence biocorrosion of and biofilm formation by relevant organisms. First results are promising with higher rates of corrosion reduction and better long-term stability compared to natural EPS-extracts.

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