Mechanism of Long-Term Corrosion Protection for Silicone Epoxy Coatings Reinforced by BN-PDA-CeO2 Ternary Composites in Harsh Environments

TL;DR

A new coating material using a ternary composite of boron nitride, polydopamine, and cerium dioxide provides excellent long-term corrosion protection for metals in harsh environments.

Contribution

A novel BN-PDA-CeO2 ternary composite was developed to enhance corrosion protection through a synergistic multi-scale mechanism.

Findings

The composite coating achieved a corrosion inhibition efficiency of 99.96% for 2024 aluminum alloy.

After 120 days in NaCl solution, coating resistance and charge transfer resistance were significantly higher than in traditional coatings.

DFT calculations revealed the synergistic roles of PDA, CeO2, and Ce3+ in corrosion inhibition.

Abstract

Corrosion in harsh environments causes global economic losses exceeding 3 trillion US dollars annually. Traditional silicone epoxy (SE) coatings are prone to failure due to insufficient physical barrier properties and lack of active protection. In this study, cerium dioxide (CeO2) was in situ grown on the surface of hexagonal boron nitride (h-BN) mediated by polydopamine (PDA) to prepare BN-PDA-CeO2 ternary nanocomposites, which were then incorporated into SE coatings to construct a multi-scale synergistic corrosion protection system. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) confirmed the successful preparation of the composites, where PDA inhibited the agglomeration of h-BN and CeO2 was uniformly loaded. Electrochemical tests showed that the corrosion inhibition efficiency of the extract of this composite for 2024 aluminum alloy reached 99.96%. After immersing the composite coating in 3.5 wt% NaCl solution for 120 days, the coating resistance (Rc) and charge transfer resistance (Rct) reached 8.5 × 109 Ω·cm2 and 1.2 × 1010 Ω·cm2, respectively, which were much higher than those of pure SE coatings and coatings filled with single/binary fillers. Density functional theory (DFT) calculations revealed the synergistic mechanisms: PDA enhanced interfacial dispersion (adsorption energy of −0.58 eV), CeO2 captured Cl− (adsorption energy of −4.22 eV), and Ce3+ formed a passive film. This study provides key technical and theoretical support for the design of long-term corrosion protection coatings in harsh environments such as marine and petrochemical industries.

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