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

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.

Automated summary

The corrosion rate of steel in saline solutions can be reduced and its lifetime can be enhanced by using plant-sourced organic inhibitors. However, the performance of plant-sourced organic inhibitors in neutral chloride solutions is not satisfactory. To overcome this, metal cations, such as Zinc, are used to enhance the corrosion inhibition effect. In this study, the combination of Sinapis arvensis seed extract and Zinc was used to inhibit chloride ions from corroding mild steel. The results showed that a protective film consisting of the extract and Zinc was formed on the steel surface, improving its resistance against saline attack. The study also investigated the interaction between the extract and Zinc, as well as the morphological changes on the steel surface after introducing the extract and Zinc.