ANAEROBIC MICROBIAL INFLUENCED CORROSION OF OIL PIPELINE STEEL INHIBITIONS WITH Manniphyton fulvum mull LEAVES ETHANOL EXTRACT AND AQUEOUS EXTRACT

Anaerobic microbial influenced corrosion of oil pipeline steel inhibitions with Manniphyton fulvum mull leaves ethanol extract and aqueous extract each and respectively was studied using gravimetric and media absorbance examination techniques. The test organism Desulphurvibro species were isolated from corroded pipeline steel immersed in crude oil and water mixture sample, collected from Agip drilling site in Ahoda Porthacourt, Rivers state, Nigeria. Postgate medium was used for the isolation of the organism, and the coupons used for the study were prepared from the rusted pipeline steel. Absorbance results of the media containing the plant extract (ethanol extract and aqueous extract each) are lower than the absorbance result of the blank medium (without the extract). The decrease in absorbance is suggested to be, as a result of inhibition of the growth of sulphate reducing bacteria (Desulphurvibro species) by the plant extract in the media, which leads to fewer bacteria that obstructs the passage of light through the medium. Gravimetric results showed decrease in weight loss and corrosion rate of the pipeline steel in the plant extract containing media, from the weight loss and corrosion rate of the steel immersed in the blank medium (without extract). The decrease in corrosion rate was more pronounced as the concentrations of the extracts in the media increased from 10 mg/ml to 500 mg/ml. Inhibition efficiency of the plant extract increased as concentrations of plant extract increased. Meanwhile, increase in inhibition efficiency was found to be more susceptible in ethanol extract than aqueous extract. The microbial influenced corrosion is inhibited by Manniphyton fulvum mull extract by both inhibition of the growth of the sulphate reducing bacteria cells and adsorption of the plant extract molecules, on the metal surface forming a barrier between the metal and the invading bacteria. The adsorption of the plant extracts both ethanol extract and aqueous extract best fitted into Langmuir adsorption isotherm.