Recent research on gas-phase nanomaterials in anti-corrosion coatings
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Following the Hong Kong-Zhuhai-Macao Bridge, the world-class cross-sea project that combines bridges, islands, tunnels, and underwater connections – the Deep Bay–Zhongshan Channel – faces numerous challenges in complex marine environments, where chemical corrosion, biological corrosion, mechanical corrosion, and electrochemical corrosion occur at all times. To ensure that this infrastructure has a long service life, corrosion prevention is a crucial element. As a special material designed for use in harsh corrosive environments, anti-corrosion coatings play a vital role in protecting pipelines and storage tanks in the petrochemical industry, railway and rail transit systems, highway and bridge steel structures, building steel frameworks, power generation projects, offshore engineering, and the automotive industry. Their importance is self-evident. Among them, China is a major country in the coatings industry and also possesses the world’s largest market for anti-corrosion coatings, offering very promising prospects for this sector. In actual production, anti-corrosion coatings are classified into conventional anti-corrosion coatings and high-performance anti-corrosion coatings based on the application environment; they are categorized by raw materials as epoxy resin, polyurethane, zinc-rich paint, acrylic, silicone chloride, alkyd, and fluorocarbon anti-corrosion coatings; and they are divided by solvents into coatings using ordinary solvents, water-soluble coatings, high-solid-content coatings, and solvent-free anti-corrosion coatings. For anti-corrosion coatings, how to increase the application efficiency of these coatings during installation and enhance the corrosion resistance of the resulting paint film are common challenges encountered in their use in various applications. So, can vapor-phase silica solve these problems? The latest research conducted by Hubei Huifu Nanomaterials Co., Ltd. will provide an answer. HF Nano’s technical staff have recently conducted applied research and practical testing on solvent-based epoxy anti-corrosion coatings. First, experiments were conducted to examine the thickening and thixotropic effects of fumed silica on the performance of anti-corrosion coatings (Figure 1). By adding 0.8% fumed silica to the anti-corrosion coatings, viscosity and thixotropy tests were carried out compared with the control sample and competing products. The researchers at HuiFu Nano found that fumed silica could significantly increase the viscosity and thixotic properties of the coatings; at the same addition level, the performance of HB-139 was comparable to that of competing product A, and better than that of competing product B.
Subsequently, the sagging behavior of solvent-based epoxy anti-corrosion coatings was tested (Figure 2), and silica in the gas phase significantly improved the resistance to sagging in epoxy zinc-rich coatings. The blank sample showed severe sagging, with a sagging value of 75μm; HB-139, as well as Competitor A and Competitor B, exhibited no signs of sagging at all, indicating that their sagging values were ≥275μm, which allows for effective prevention of the paint film from flowing or dripping during application. In the experiments on the appearance of paint films (Figure 3), technicians applied a zinc-rich paint film containing 0.8% fumed silica onto tinplate, with a thickness of 25 μm. Through comparison between Group A and Group B, the control sample without added fumed silica contained protruding particles and exhibited significant reflectivity, while the sample with fumed silica had no particles, no notable reflectivity, and presented a good matte finish. Through the comparison between groups C and D, the control coating film without added fumed silica developed thick edges and an uneven surface, whereas the coating film with the additive was smoother. It can be seen that adding fumed silica to zinc-rich paints effectively enhances the directional arrangement of zinc powder, improving the uniformity of the paint film (such as color variation), the particle structure, and glossiness; it also significantly reduces the phenomenon of thick edges.
In the investigation into the settlement resistance of epoxy anti-corrosion coatings (Figure 4), sedimentation of the pigments occurred in all four groups of samples after 15 days of heat storage. Compared with the control sample, the addition of fumed silica improved the sedimentation behavior of all coatings; the control sample exhibited hard sedimentation, while those containing fumed silica showed soft sedimentation. HB-139 has a certain advantage over competing products A and B in terms of anti-sedimentation performance. In the study on the salt spray resistance of epoxy anti-corrosion coatings (Figure 5), after 1500 hours of salt spray testing and observation, the researchers at Hui Fu Nano found that the control sample developed bubbling and rusting after 300 hours; Sample B from a competing brand showed bubbling after 800 hours, while neither HB-139 nor Sample A from the competing brand exhibited any abnormalities during the 1500-hour testing period.