Synthesis of a novel Ce(iii)/melamine coordination polymer and its application for corrosion protection of AA2024 in NaCl solution

Abstract

We present the synthesis of a new cerium(III)–melamine coordination polymer (CMCP) by a mixed-solvothermal method and its characterization. Characterization techniques included Raman, Fourier Transformation Infra-Red (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM), in which the change in the electronic environment and the crystallinity were tracked. The characterization results confirm the coordination of cerium(III) with melamine through –NH₂ groups, instead of the N atoms of the triazine ring, for which we propose a mechanism of interaction. In addition, Biovia Materials Studio package was applied to determine and investigate the molecular structure of the CMCP. All simulations were done using COMPASS force-field theory and atom-based method for summation of electrostatic and van de Waals forces. The application of the CMCP for the corrosion inhibition of AA2024 in 3.5% NaCl solution was tested using the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results point out that the presence of cerium as cerium(III) in the CMCP structure plays the fundamental role of inhibition, whereby the inhibition mechanism occurs by cathodic oxidation of Ce(III) to Ce(IV) and cyclic reduction of Ce(IV) to Ce(III) by melamine part of CMCP.