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

Abstract

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.