Efficacy of Aloe Vera extract and scent leaf extract as biocorrosion inhibitors were evaluated using stainless steel coupons as the target surface/substratum. Stainless steel coupons were weighed and immersed in suspension containing (1) iron oxidizing bacteria (IOB) and scent leaf extract (SLE), (2) IOB and aloe vera extract (ALE), (3) sulfate reducing bacteria (SRB) and SLE and (4) SRB and ALE respectively. Scent leaf and aloe vera extracts had 3.9% and 1.4% yield respectively. IOB had log10 IOB counts that ranged from 4.19 to 5.16 cfu/ml while SRB had log10 counts range of 4.11 to 5.16 cfu/ml. IOB isolates identified are Leptothrix sp., Sphaerotilus sp. and Gallionella sp. while that of SRB are Desulfovibrio sp., Desulfotomaculum sp. and Desulfovibrio sp. In IOB culture, conductivity increased from 1.0130 to 3.90 s/m for ALE and 1.0140 to 2.80 s/m for SLE. The pH increased from 7.61 to 7.87 for ALE and 7.72 to 7.96 SLE medium. In SRB suspension, conductivity decreased for Aloe vera and increased in scent leaf. Iron II ions involving IOB in stainless steel coupons with aloe vera decreased by 56.7% and decreased by 48.9% for scent leaf medium while iron II ion involving SRB in suspension with ALE and SLE decreased by 43.01% and 46.52% respectively. Stainless steel immersed in SLE containing IOB had 272.7 mpy biocorrosion inhibitions than those immersed in ALE and IOB (167.8 mpy). Biocorrosion was significantly (p<0.05) higher in suspension containing IOB and SLE (99.1%) than in IOB and ALE suspension (74.8%). Steel immersed in SLE and SRB biocorroded at 206.6 mpy (64.2%) and in ALE and SRB suspension, it biocorroded at 344.4 mpy (63.7%). Bicorrosion monitoring and mitigation using locally sourced plant extracts as inhibitors could significantly reduce the spate of pipeline ruptures along pipeline Right of Ways in the Nigerian petroleum industries.
Keywords: Plant extracts, Biocorrosion inhibitors, Pipelines ruptures, Stainless steel coupons