Experimental and theoretical evaluation of aqueous black mustard seeds extract as sustainable-green inhibitor for mild steel corrosion in H2SO4 acid solutions

The inhibitory potential of aqueous black mustard seed (BMS) extract on mild steel corrosion in H2SO4 solutions was tested using various chemicals (Hydrogen Evolution, HE, and Weight Loss, WL) and electrochemical (Electrochemical Impedance Spectroscopy, EIS, and Potentiodynamic Polarization, PDP) methods. The adsorption process was characterized using scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and contact angle technique. Computational studies were also used to improve the visualization of the adsorption mechanism of the active components found in BMS on the metal surface. The results showed that aqueous BMS extract had a superior ability to inhibit mild steel corrosion in 2 M H2SO4 (IE% = 94.83 at 3.5 g/L). Polarization outcomes demonstrated that the BMS functioned as a mixed-type inhibitor. The findings are consistent with the Langmuir adsorption isotherm. FT-IR, contact angle, and SEM successfully showed the formation of a dense and ordered BMS-adsorbed film. The calculated E-a in the absence and presence of BMS revealed that physisorption and chemisorption played a role in the inhibition mechanism. Using DFT quantum-chemical calculations and MD simulations, a relationship can be established between the electronic structure of Sinigrin, the main component in BMS, and its ability to inhibit corrosion. BMS extract showed exceptional inhibitory activity in a wide range of H2SO4 concentrations. One of the important aspects of this study is the possibility of applying BMS as a greener alternative to design environmentally friendly materials in working on corrosion problems of metallic equipment in acidic environments.