Neem extract as an inhibitor for biocorrosion influenced by sulfate reducing bacteria: A preliminary investigation

This work investigates the inhibition effect of Neem (Azadirachta indica) extract on microbiologically influenced corrosion (MIC) of API 5L X80 linepipe steel by a sulfate-reducing bacterial (SRB) consortium. The SRB consortium used in this study included three phylotypes; Desulfovibrio africanus, Desulfovibrio alaskensis and Desulfomicrobium sp. Steel coupons were incubated in the presence of the SRB consortium without and with 4 wt.% Neem extracts for different periods of time. The morphology, compositions of the interfaces and subsequent corrosive pitting were characterized with field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS). In addition, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and open circuit potential (OCP) were used to investigate the in situ corrosion behavior under the two different conditions. The results revealed that Neem extract has the capability to reduce the biocorrosion rate by approximately 50%. Neem has significantly reduced the propensity of linepipe steel to SRB caused MIC by minimizing the cell growth and has subsequently suppressed the sulfide productions, sessile cell density and biofilm development.