Effect of Inorganic Particles in the Protection Behavior of Epoxy-based Composite Coatings

Abstract

This research focuses on understanding the different mechanisms underlying the performance of two epoxy-based coatings applied on different substrates. The magnesium-rich coatings applied to aluminum 7075 T6 work aims to use electrochemical methods, such as open circuit potential and electrochemical impedance spectroscopy (EIS) to characterize the real-time performance of a magnesium-rich epoxy coating primer (MgRP) varying in magnesium content and exposed to a neutral buffer solution. The magnesium-rich primer (MgRP) illustrates the evolution of the sacrificial and barrier effects with different amounts of Mg particles and carbon nanotubes (CNTs) added to the epoxy matrix. The results can be used to characterize the performance of this coating/substrate system under a neutral environment condition. The epoxy-trimetallic oxide (Epoxy-TMO) coatings were synthesized and integrated on stainless steel surface in order to study the effect of the trimetallic oxides (TMO) ZrO2/TiO2/ZnO (Z2T) for the barrier properties of the epoxy polymer matrix. The different ratios of TMO were synthesized using the ball-milling method and later dispersed on the polymer matrix. Elemental characterization and morphological studies of the oxides were performed with x-ray diffraction (XRD) and SEM. The thickness of the epoxy-TMO coatings was estimated using SEM cross-sectional imaging. UV-Vis was performed to study the light absorption properties of the coatings. The effect of the addition of these oxides on the electrochemical behavior was studied in a 3.5 wt% NaCl solution using electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR). The epoxy-TMO coating with a ratio of 50/40/10 Z2R hybrid showed the highest corrosion resistance and the formation of a second protective barrier following 28 days in the corrosive environment. The proposed mechanisms consider the effect of the oxides in corrosion control actions and the natural barrier effect due to the polymer matrix. The results show that the combination of these three oxides in the polymer matrix increases the barrier properties.