Neem extract as a green inhibitor for microbiologically influenced corrosion of carbon steel API 5LX in a hypersaline environments

In this study, the efficiency of neem extract to inhibit the corrosion of carbon steel API 5LX in the presence of different bacterial strains (Bacillus subtilis A1, Streptomyces parvus B7, Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3) were evaluated. 150 ppm of Azadirachta indica leave extract (AILE) was identified as minimal inhibitory concentration for the bacterial strains B. subtilis A1, S. parvus B7, P. stutzeri NA3 and A. baumannii MN3. Weight loss, electrochemical studies including potential measurements, potentiodynamic polarization and impedance and surface analysis includes Fourier transform infrared spectroscopy (FT-IR) were used to examine the corrosion inhibition efficiency (IE) of AILE on carbon steel API 5LX. The individual bacterial strains and mixed consortium had showed severe corrosion of carbon steel API 5LX in hypersaline environment. In contrast with AILE, the IE of abiotic control and mixed consortia were about 81% and 72% respectively. The corrosion rate was observed as increased trends in presence of all bacterial strains (0.179 mm/y) when compared to abiotic system with AILE system (0.012 mm/y). X-ray diffraction spectroscopy (XRD) confirms that all bacterial strains has accelerates the corrosion by the production of higher intensity peaks of corrosion products when compared to AILE systems. FT-IR data reveals that AILE extracts consists of azadirachtin and other phytochemical compound which was play a key role in control of bacterial biofilm on metal surface and thus leads to inhibit corrosion process. This is the first report on the application of AILE as a natural, eco-friendly corrosion inhibitor with antibacterial activities to control microbiologically influenced corrosion in hypersaline environment of oil reservoir.