Fabrication of Protective Organic Layer Using Schiff-Base Metal Complex Responsible for Excellent Corrosion Performance: Experimental and Theoretical Perspectives.

The effectiveness of a copper(II) complex with a Schiff base derived from 2-amino-4-phenyl-5-methylthiazole and salicylaldehyde (APMS) as a corrosion inhibitor for XC18 steel in an HCl solution was investigated. Experimental findings indicated a slight negative correlation between inhibition efficiencies in 1 M HCl and temperature but a positive correlation with both inhibitor concentration and immersion time, respectively. The weight loss measurement revealed that APMS achieved a maximum inhibition rate of 92.07% at 303 K. A fitting analysis demonstrated that APMS adheres to the Langmuir adsorption isotherm. The electrochemical results revealed an enhanced inhibitive performance of APMS, with the efficiency increasing as concentrations increased, ultimately reaching a peak of 94.47% at 5 × 10-3 mol L-1. Potentiodynamic polarization measurements revealed that APMS acted as a mixed-type inhibitor without affecting the corrosion mechanism. Scanning electron microscopy investigations of the metal surfaces corroborated the presence of an adsorbed organic layer. Advanced theoretical calculations utilizing density functional theory and first-principles density-functional tight-binding were conducted to gain insights into the behavior of APMS on the metal surface. APMS derives its advantages from crucial inter- and intramolecular interactions, resulting in the formation of a resilient adsorption layer, in line with the experimental findings. It is found that the presence of the APMS-based inhibitor exhibits a significant synergistic corrosion inhibition effect. The current study offers a design direction for enhancing the structural characteristics of Schiff base metal complexes, laying the groundwork for multifunctional frameworks to minimize corrosion rates with considerations for real-world use and cost-efficiency. The ability to replace harmful, expensive constituents with sustainable, and cost-effective organic alternatives represents a significant outcome of this study.

A Novel Coating System Based on Layered Double Hydroxide/HQS Hierarchical Structure for Reliable Protection of Mg Alloy: Electrochemical and Computational Perspectives.

Growing research activity on layered double hydroxide (LDH)-based materials for novel applications has been increasing; however, promoting LDH layer growth and examining its morphologies without resorting to extreme pressure conditions remains a challenge. In the present study, we enhance LDH growth and morphology examination without extreme pressure conditions. By synthesizing Mg-Al LDH directly on plasma electrolytic oxidation (PEO)-treated Mg alloy surfaces and pores at ambient pressure, the direct synthesis was achieved feasibly without autoclave requirements, employing a suitable chelating agent. Additionally, enhancing corrosion resistance involved incorporating electron donor-acceptor compounds into a protective layer, with 8-Hydroxyquinoline-5-sulfonic acid (HQS) that helps in augmenting Mg alloy corrosion resistance through the combination of LDH ion-exchange ability and the organic layer. DFT simulations were used to explain the mutual interactions in the LDH system and provide a theoretical knowledge of the interfacial process at the molecular level.

Development of Natural Plant Extracts as Sustainable Inhibitors for Efficient Protection of Mild Steel: Experimental and First-Principles Multi-Level Computational Methods.

In the present work, we present the superior corrosion inhibition properties of three plant-based products, Fraxinus excelsior (FEAE), Zingiber zerumbet (ZZAE), and Isatis tinctoria (ITAE), that efficiently inhibit the corrosion of mild steel in phosphoric acid. The anti-corrosion and adsorption characteristics were assessed using a combination of experimental and computational approaches. Weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy methods were used to evaluate the inhibitive performance of the inhibitors on the metal surface. Then, both DFT/DFTB calculations and molecular dynamic simulations were further adopted to investigate the interaction between organic inhibitor molecules and the metal surface. The protective layers assembled using the active constituents, such as carbonyl and hydroxyl groups, of the three plant-based products offer high electrochemical stability at high temperatures and robust protection against aggressive acidic solutions. All electrochemical measurements showed that the inhibition performance of extracts increased by increasing their concentration and improved in the following order: FEAE > ZZAE > ITAE. Further, these extracts worked as mixed-type inhibitors to block the anodic and cathodic active sites on the mild steel surface. Multi-level computational approaches revealed that FEAE is the most adsorbed inhibitor owing to its ability to provide electron lone pairs for electrophilic reactions. The experimental and theoretical results showed good agreement. These results indicate the possibility of replacing conventional compounds with natural substituted organic products in the fabrication of hybrid materials with effective anti-corrosion performance.