Investigating inhibition characteristics of Butea monosperma leaf extracts to retard stainless steel biocorrosion in the presence of sulfate-reducing bacteria

Abstract

The influence of sulfate-reducing bacteria Desulfovibrio desulfuricans on stainless steel SS 202 corrosion in neutral media was studied in detail using weight loss and electrochemical routes. The bacterial activity resulted in material loss with an average rate of 0.015 mm/year. The scanning electron microscopy (SEM) analysis showed a significant increase in the sessile bacterial population with the immersion period. Use of 500 ppm palash (Butea monosperma) leaf extract (PLE) reduced the average corrosion rate to 0.002 mm/year. SEM analysis showed a very thin external film formation in the presence of the inhibitor. The X-ray photoelectron spectroscopy studies confirmed the presence of corrosion products such as Fe2O3 and FeS. The gas chromatography–mass spectrometry studies showed the dominant percentage of various terpenoids along with vitamin E as the main components of the PLE. Electrochemical analysis showed the existence of a diffusion barrier. The resistance offered by the diffusion barrier is high in the inhibited sample when compared to uninhibited samples.

Keywords

• biocorrosion
• butea monosperma
• electrochemical study
• x-ray photoelectron spectroscopy