Augmentation in corrosion inhibition efficiency in gram-negative bacterial strains influenced adsorption of Saccharum officinarum bagasse extract at the interphase of copper metal and a mild corrosive environment

Plant extracts and bacterial biofilm are acknowledged to offer impressive corrosion-inhibitory activities. However, anticorrosive properties of their combination are still less reported. Thus, in the present study, we aimed to evaluate the corrosion inhibition efficiency of Saccharum officinarum bagasse (SOB) plant extract, Pseudomonas chlororaphis (P. chlororaphis), and Bacillus coagulans (B. coagulans) individually and in combination (SOB+P. chlororaphis) and (SOB+B. coagulans) using copper sheets in different acidic solutions (pH 5.5) and at three different temperatures (300 K, 305 K, and 310 K). The weight loss and electrochemical measurements were carried out to evaluate the corrosion rate and inhibition efficiencies. Alteration in the surface morphology of copper sheets was analyzed employing Fourier transform infrared (FTIR) spectroscopy, UV visible spectroscopy, scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). Amongst all, SOB extract alone exhibited the highest anticorrosive efficiency, whereas the combination of SOB with P. chlororaphis revealed excellent inhibition efficiency. Weight loss studies indicated that at 300 K, the combination of SOB extract with P. chlororaphis significantly reduces the corrosion rate up to 11.90% with the highest inhibition efficiency of 88.09%. However, with an increase in temperature, i.e. 310 K, the corrosion rate diminishes to 13.04% with inhibition efficiency of 86.95% for 500 µL concentration in HNO₃ solution. The combination of an SOB extract with P. chlororaphis displayed a maximum corrosion inhibition efficiency of 85.11% in the potentiodynamic polarization (PP) study and 88.23% in the electrochemical impedance spectroscopy (EIS), respectively and found in agreement with the efficiency obtained in the weight loss study. Later, the synergistic parameter (S_Ɵ) advocated that the SOB extract and P. chlororaphis do not interact mutually whereas ∆G°_ads values suggested the physisorption of these agents on the copper plates follows Langmuir adsorption isotherm. The spectral analysis and SEM images of the copper plate revealed that the combination of SOB extract with P. chlororaphis forms a strong protective layer over its surface and prevents corrosion. In conclusion, the combination of SOB extract with P. chlororaphis holds impressive anticorrosive properties and may be explored further to attain their industrial utility.