Abstract
Anticorrosive coatings prepared by sol-gel derived approaches have become an emergent research area in the field of corrosion prevention materials. Furthermore, enhanced coating thickness can greatly improve the barrier effect of the sol-gel coatings, thus influencing their service life in industrial applications. Here, we propose the preparation of a two-layer coating system using a low-cost sol-gel derived method. The coating structure was composed of first an underlying layer incorporated with silica and titania powder as filler and pigment materials, and a second translucent topcoat containing a colloidal silica sol-gel matrix crosslinked by methyltrimethoxysilane (MTMS). This coating system was applied on Q235 carbon steel substrate by a two-step spray deposition method, resulting in an enhanced coating thickness of around 35 μm. The physical and morphological properties of the coatings were characterized using multiple techniques, including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The anticorrosion performance of the sol-gel coatings was studied by a salt spray test, outdoor exposure test and electrochemical impedance spectroscopy (EIS). Results revealed that this two-layer coating system exhibited excellent physical and anticorrosion properties, and that the topcoat played a crucial role in maintaining the barrier effect and preventing water leakage.
Highlights
Corrosion of commonly used metals, such as carbon steel, stainless steel, and aluminum alloy, poses a major threat to various applications ranging from infrastructure to machinery
The anticorrosion properties of the coating structures were investigated by salt spray test, outdoor exposure test and electrochemical impedance spectroscopy (EIS), and the results indicated that the two-layer coating system with enhanced coating thickness exhibited good corrosion prevention durability
After the pH adjustment, 134 g of MTMS was added into the mixture to initiate the hydrolysis and condensation reactions, and the reactions were allowed to continue for 8 h at room temperature under constant agitation using a tube roller mixer working at 300 RPM/min
Summary
Corrosion of commonly used metals, such as carbon steel, stainless steel, and aluminum alloy, poses a major threat to various applications ranging from infrastructure to machinery. The deposition techniques commonly used in these coating preparations were dip-coating or spin-coating [34,35,36], which usually require multiple cycles of deposition procedures, and the as-prepared coatings were often less than 20 μm in thickness [37,38,39] In this regard, sol-gel derived coatings incorporated with nano- or micro-sized filler and pigment materials and prepared using spray deposition can be a solution for creation of coating systems with higher thicknesses, enhanced anticorrosion properties, and selectable color preference. Silica and titania powder were selected as filler and pigment materials in this study due to their low-cost and good compatibility with other chemical components in this reaction system Incorporation of these filler materials into the underlying layer of the coating structure resulted in protective films with increased coating thickness and white colored appearance. Comparative EIS studies revealed that the application of the more uniform and hydrophobic topcoat played an important role in this coating system
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