Synergistic corrosion inhibition effects of the non-hazardous cerium nitrate and tannic acid polyphenolic molecules on the surface of mild-steel in chloride-containing solution: Detailed surface and electrochemical explorations

Abstract

The generation of novel inhibitive molecules that can compete with harmful conventional chromium ones has remained a serious challenge in corrosion engineering. The present study aims to develop a newfangled natural compound to hinder the aggressive consequences of steel corrosion. To this end, the synergistic effects of the eco-friendly cerium nitrate on the corrosion retardation ability of the tannic acid (TAA) were examined for the metal specimens subjected to the saline (NaCl containing) solution. The adsorption of the TAA molecules and Ce:TAA complex on the metal substrate was evaluated by FTIR analysis. The surface properties of the samples were analyzed via SEM, UV–Vis spectroscopy, GIXRD, AFM, contact angle, and the Raman spectroscopy techniques. The effectiveness of the Ce:TAA mixture on the mild steel (MS) corrosion mitigation was examined through the EIS and polarization techniques. The results showed that the minimum corrosion current density (icorr = 0.54 μA/cm2) and the maximum total resistance (Rt ~ 22 Kohm.cm2) were observed for the samples immersed in the solution containing the Ce:TAA mixture (with the 1:1 mass ratio). The complex formation between the TAA molecules and Fe/Ce cations was proved the surface studies. The contact angle of the steel samples immersed in the saline solution containing Ce:TAA mixtures increased at least threefold. The inhibition efficiencies of the independent Ce and TAA inhibitors in the saline solution was measured around 74–92% and − 16-64%, respectively, while their optimum composition showed more than 86% efficiency all over the immersion time.