Hongchang Qian

Dual-action smart coatings with a self-healing superhydrophobic surface and anti-corrosion properties

This work introduces a new self-healing superhydrophobic coating based on dual actions by the corrosion inhibitor benzotriazole (BTA) and an epoxy-based shape memory polymer (SMP). Damage to the surface morphology (e.g., crushed areas and scratches) and the corresponding superhydrophobicity are shown to be rapidly healed through a simple heat treatment at 60 °C for 20 min. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) were used to study the anti-corrosion performance of the scratched and the healed superhydrophobic coatings immersed in a 3.5 wt% NaCl solution. The results revealed that the anti-corrosion performance of the scratched coatings was improved upon the incorporation of BTA. After the heat treatment, the scratched superhydrophobic coatings exhibited excellent recovery of their anti-corrosion performance, which is attributed to the closure of the scratch by the shape memory effect and to the improved inhibition efficiency of BTA. Furthermore, we found that the pre-existing corrosion product inside the coating scratch could hinder the scratch closure by the shape memory effect and reduce the coating adhesion in the scratched region. However, the addition of BTA effectively suppressed the formation of corrosion products and enhanced the self-healing and adhesion performance under these conditions. Importantly, we also demonstrated that these coatings can be autonomously healed within 1 h in an outdoor environment using sunlight as the heat source.

Mussel-inspired superhydrophobic surfaces with enhanced corrosion resistance and dual-action antibacterial properties

In this study, a multilayer antibacterial film was assembled onto 316L stainless steel via mussel-inspired depositions of polydopamine (PDA) and silver (Ag) nanoparticles followed by post-modification with 1H, 1H, 2H, 2H-perfluorodecanethiol. The resulting surface exhibited excellent superhydrophobicity with hierarchical micro/nanostructures that were constructed by both PDA and Ag nanoparticles. The crystal structure and chemical composition of these surfaces were investigated using X-ray photoelectron spectroscopy (XPS) analysis. Potentiodynamic polarization measurements revealed that the corrosion resistance of the as-prepared surfaces were sequentially increased after each step of the fabrication process. Compared with the surface covered with only Ag nanoparticles, the superhydrophobic surfaces exhibited substantially enhanced antibacterial activity against the Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, resulting from the synergistic antibacterial actions of the superhydrophobic surface and Ag nanoparticles. The superhydrophobic surface exhibited lower cytotoxicity, compared to the surface covered with Ag nanoparticles.

Effect of surface microstructures on hydrophobicity and barrier property of anticorrosive coatings prepared by soft lithography

Enhancing the hydrophobicity of organic coatings retards their interaction with water and often leads to better protectiveness over metal corrosion. In this study, a soft lithography method was used to prepare epoxy coatings which showed surface microstructures in high replication to sandpapers. The effect of microstructures on coating’s hydrophobicity and barrier property was investigated. Compared to flat coatings, the microstructured coatings showed much higher water contact angles, which further increased with finer sandpapers. Determined by electrochemical impedance spectroscopy (EIS), the flat coating exhibited a higher anticorrosive performance than the microstructured coatings. With the use of finer sandpaper, the groove size of the corresponding microstructured coating was reduced. And a lower anticorrosive performance was observed since more defects might be formed in a given area of coating during the imprinting process. As the groove size of the coatings was further decreased to 5.7 µm, the microstructures became too small for water to easily penetrate through. Therefore, trapped air acted as an additional barrier and contributed to an increased anticorrosive performance compared to other microstructured coatings.

Double layer water-borne heat insulation coatings containing hollow glass microspheres (HGMs)

Purpose This study aims to construct a double layer heat insulation coating based on hollow glass microspheres (HGMs) and to investigate the effect of particle size on barrier property and heat insulation performance. Design/methodology/approach The waterborne double layer coating was composed of an anticorrosive epoxy ester primer and an HGM-containing silicone acrylic topcoat. With varied HGM sizes (20 μm, 40 μm, 60 μm and a 1:3 w/w mixture of 20 and 60 μm particles), the coating was immersed in 3.5 wt% NaCl solution for 28 days and was then subjected to a salt spray test for 450 h. The barrier properties of the coating were evaluated through electrochemical impedance spectroscopy. Heat insulation performance was examined using a self-made device. Findings The addition of HGMs decreased the barrier properties of the coating by creating particle/resin interfaces for water penetration. In the HGMs-containing coatings, the use of larger HGMs showed relatively good barrier properties because of the lower particle density. The coating with smaller particles yielded a higher heat insulating capacity as indicated by lower equilibrium temperatures. Research limitations/implications Future work will be focused on improving the barrier properties of the coating. Field exposure tests should also be performed to assess the long-term performance of the coating. Practical implications The mechanical properties of the coatings in this study also implied that HGMs can be used to develop scratch-resistant and impact-resistant coatings. Other potential applications for further studies include the uses of HGMs for coatings with improved fire retardancy and electromagnetic interference shielding. Originality/value A double layer coating was developed to provide balanced performance on both anticorrosion and heat insulation. The effects of HGM size were particularly highlighted.

Triple-Action Self-Healing Protective Coatings Based on Shape Memory Polymers Containing Dual-Function Microspheres

In this study, a new self-healing shape memory polymer (SMP) coating was prepared to protect the aluminum alloy 2024-T3 from corrosion by the incorporation of dual-function microspheres containing polycaprolactone and the corrosion inhibitor 8-hydroxyquinoline (8HQ). The self-healing properties of the coatings were investigated via scanning electron microscopy, electrochemical impedance spectroscopy, and scanning electrochemical microscopy following the application of different healing conditions. The results demonstrated that the coating possessed a triple-action self-healing ability enabled by the cooperation of the 8HQ inhibitor, the SMP coating matrix, and the melted microspheres. The coating released 8HQ in a pH-dependent fashion and immediately suppressed corrosion within the coating scratch. After heat treatment, the scratched coating exhibited excellent recovery of its anticorrosion performance, which was attributed to the simultaneous initiation of scratch closure by the shape memory effect of the coating matrix, sealing of the scratch by the melted microspheres, and the synergistic effect of corrosion inhibition by 8HQ.

Corrosion Behavior of X80 Steel with Coupled Coating Defects under Alternating Current Interference in Alkaline Environment

The corrosion behavior of X80 steel in the presence of coupled coating defects was simulated and studied under the interference of alternating current (AC) in an alkaline environment. The results from electrochemical measurements showed that the electrode potential of the coating defect with the smaller exposed area was lower than that with the larger area, which indicated that the steel with the smaller coating defect was more prone to corrosion. The result of weight loss tests also showed that the smaller coating defect had induced a higher corrosion rate. However, the corrosion rate of X80 steel at the larger coating defect decreased gradually with the increase of the larger defect area at a constant smaller defect area. The corrosion morphology images showed that the coating defects with smaller areas suffered from more severe pitting corrosion.