Biocorrosion Inhibitory Potential of Aqueous Extract of Phyllanthus amarus against Acid Producing Bacteria

Abstract

Biocorrosion is a form of corrosion of metallic and concrete materials mediated by microorganisms. Acid producing bacteria are major culprits in the corrosion of materials in the environment. This study focused on the inhibition of biocorrosion by acid producing bacteria using aqueous extract of Phyllanthus amarus (PAAE). Acid producing bacteria were isolated from produced water samples collected from oilfields located in Niger Delta, Nigeria. Multiple fermentation tube technique was adopted for the isolation of the acid producing bacteria using phenol red dextrose broth as culture broth medium. The gravimetric analysis was performed with different concentrations of the plant extract incorporated in universal culture bottles containing broth, sample and carbon steel coupon. The setup was incubated at 20ºC, 30ºC and 40ºC for 7 days and for 14 days. The least corrosion rate (CR) at 20ºC, 30ºC and 40ºC for the 7 days test were 1.446mp/y (80mg/ml PAAE); 27.558mp/y (5 mg/mlLeu+20 mg/ml PAAE) and 5.134 mp/y (80 mg/ml PAAE) with corresponding inhibition efficiency (IE) of 81.92, 87.750 and 80.91 respectively. For the 14 days, the CR values at 20ºC, 30ºC and 40ºC were: 3.192mp/y (5mg/mlLeu+20mg/ml PAAE); 1.458 mp/y (5 mg/mlLeu + 20 mg/ml PAAE) and 117.345mp/y (5 mg/mlLeu + 20 mg/ml PAAE) with corresponding IE of 86.09, 83.87 and 98.89 respectively. The results obtained show that the extract could be considered as a good inhibitor for the biocorrosion of carbon steel mediated by acid producing bacteria.