Sinapis arvensis (Mustard) extract derived bio-molecules linked Zinc-II ions; Integrated electrochemical & surface investigations

Abstract

One way to diminish the steel corrosion rate and enhance its lifetime in the saline (NaCl-based) solutions is by inserting the plant-sourced organic inhibitor into the aggressive media. However, the plant-sourced organic inhibitor's performance in neutral chloride solutions is not promising, so, the metal cations, i.e. Zinc, were used for aiding the synergistic corrosion inhibition effect. In the current work, mild steel (MS) substrate was inhibited against chloride ions by utilizing different ratios of Sinapis arvensis (Mustard) seed extract (SASE) and Zinc (Zn) combinations.The microstructures of the immersed samples were investigated by FE-SEM, EDS, GIXRD, and AFM analysis. The results affirmed that a protective hybrid film comprising of SASE and Zn was created over the MS surface. The FT-IR test and UV–Visible analysis were utilized for studying the SASE-Zn interaction type and electro-transitions of SASE and SASE:Zn complexes.According to the EIS analysis for the protected sample by 200–600 ppm SASE:Zn complexes, the inhibited samples resistance in front of saline attack (3.5 % sodium chloride) was improved about 85% after 24 h of immersion. Besides, the Tafel curves showed both anodic and cathodic inhibitions against corrosion, confirming the mixed-mode protection where 88% effectiveness was obtained after introducing 200–600 ppm SASE:Zn complexes. Also, the results of morphological analysis displayed the formation of a more smooth protective layer over the MS substrate after adding 200–600 ppm SASE: Zn to the saline solution. On another side, the results of FT-IR and UV–Vis results showed successful interactions between SASE and Zn cations. Furthermore, the outcome of the Raman test illustrated the presence of both D and G bands after SASE: Zn adsorption over the MS substrate.