Stevioside–Zn2+ system as an eco-friendly corrosion inhibitor for C1020 carbon steel in hydrochloric acid solution

Abstract An effective and biodegradable Stevioside from Stevia leaf was evaluated as a potential pickling inhibitor in combination with the Zn2+ cation for C1020 carbon steel (CCS). Considering its naturally occurring, cheap and environmentally safe properties, Stevioside has the potential to be widely used to inhibit the CCS corrosion in HCl solutions. The corrosion inhibition performances of Stevioside and Stevioside–Zn2+ were studied with the use of weight loss test, electrochemical techniques, and surface analysis methods. The results demonstrated an incorporation of Zn2+ component into the Stevioside layer can evidently improve the uniformity and anti-corrosion properties (i.e., 76.59% versus 95.68%). The optimal molar ratio of Stevioside/Zn2+ was found to be 1:2, and the highest inhibition efficiency was 95.68% evidenced by electrochemical test. Polarization diagrams revealed that the Stevioside and Stevioside–Zn2+ behaved as mixed type inhibitors and mainly inhibited the anodic process. The surface morphology by SEM, SECM and XPS confirmed the effectiveness of the inhibitor. Molecular dynamics simulations disclosed that the inhibitor retard the CCS corrosion during the descaling process through the mechanism donor-acceptor interaction.