Investigation of bio-corrosion in galvanized steel by Desulfovibrio desulfuricans and its mitigation by Butea monosperma leaf extract as green inhibitor

This work is intended to examine the microbially influenced corrosion on galvanized steel (GS) caused by sulfate-reducing bacteria (SRB). The efficacy of Butea monosperma (palash) leaf extract to mitigate the corrosion caused by Desulfovibrio desulfuricans was investigated in modified Barr's medium. Weight loss and electrochemical analysis were performed to check the corrosion rate at regular time intervals. SEM images were performed to understand the level of deterioration of the metal surfaces. Image analysis of the unprotected sample showed the presence of pits. From the gravimetric study, the maximum inhibition efficiency (IE) of 98% was obtained with 500 ppm of Palash leaf extract for the fourth-week sample. With the addition of 500 ppm of palash extract, the sulfide concentration decreases to 0 ppm from 123 ppm. Outcomes of potentiodynamic polarization (PP) studies showed that the extract disturbs the cathodic reaction significantly and moves the corrosion potential to a more negative value and IE was about 71% from PP studies. FTIR and GC-MS analysis was performed to recognize the plausible chemical compounds present in Palash leaf powder. EIS results confirmed that the resistance to corrosion increases substantially with the addition of inhibitor. The mechanism for corrosion inhibition has been proposed based on the results obtained.