ABSTRACT

 The inhibitive/ adsorptive behavior of Bryophyllum pinnatum leaves extract on microbial corrosion of oil pipeline steel in anaerobic medium were studied using UV Spectrophotometer, Gravimetric and Scanning Electron Microscope (SEM). The test organism Desulphovibro species was isolated from corroded pipeline steel supplied by Shell Petroleum Development Company Limited (SPDC). Postage medium was used for the isolation of the organism and the coupons used for the study were prepared from the rusted pipeline steel. The absorbance in the media containing Bryophyllum pinnatum leaves extract from the absorbance values of the blank uninhibited medium. The decrease in absorbance indicates inhibition growth of the sulfate reducing bacteria in the incubated medium based on the fact that the high absorbance showed by blank medium wad as a result of more growth of the Desulphovibrio species which then obstruct the passage of light. The gravimetric results showed decreased in weight loss and corrosion rate in medium containing Bryophyl/um pinnatum leaves aqueous and ethanol extract respectively when compared to the corrosion rate of the coupon immersed in the extract free medium (blank). The inhibition efficiency of the plant extract ethanol and aqueous respectively increased with increase in extract concentration was found to be more susceptible in ethanol extract. The Scanning Electron Microscope (SEM) results showed an evidence of pitting corrosion on the surface of the coupons. The coupon immersed in blank sulfate reducing bacteria incubated medium, has rougher surface with greater number of pits corroded surface than the one's immersed in the Bryphyllum pinnatum containing media. The corrosion inhibition by Bryophyllum pinnatum leave extracts is suggested to result from its phytochemicals that facilitated adsorption behavior on the metal surface because of its organic nature protecting the metal from invading microbial. The extract adsorption fitted best in Langmuir adsorption isotherm.