Dawei Zhang

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.

Accelerated corrosion of 2205 duplex stainless steel caused by marine aerobic Pseudomonas aeruginosa biofilm.

Microbiologically influenced corrosion (MIC) of 2205 duplex stainless steel (DSS) in the presence of Pseudomonas aeruginosa was investigated through electrochemical and surface analyses. The electrochemical results showed that P. aeruginosa significantly reduced the corrosion resistance of 2205 DSS. Confocal laser scanning microscopy (CLSM) images showed that the depths of the largest pits on 2205 DSS with and without P. aeruginosa were 14.0 and 4.9μm, respectively, indicating that the pitting corrosion was accelerated by P. aeruginosa. X-ray photoelectron spectroscopy (XPS) results revealed that CrO3 and CrN formed on the 2205 DSS surface in the presence of P. aeruginosa.

Microbiologically Influenced Corrosion of 2707 Hyper-Duplex Stainless Steel by Marine Pseudomonas aeruginosa Biofilm

Microbiologically Influenced Corrosion (MIC) is a serious problem in many industries because it causes huge economic losses. Due to its excellent resistance to chemical corrosion, 2707 hyper duplex stainless steel (2707 HDSS) has been used in the marine environment. However, its resistance to MIC was not experimentally proven. In this study, the MIC behavior of 2707 HDSS caused by the marine aerobe Pseudomonas aeruginosa was investigated. Electrochemical analyses demonstrated a positive shift in the corrosion potential and an increase in the corrosion current density in the presence of the P. aeruginosa biofilm in the 2216E medium. X-ray photoelectron spectroscopy (XPS) analysis results showed a decrease in Cr content on the coupon surface beneath the biofilm. The pit imaging analysis showed that the P. aeruginosa biofilm caused a largest pit depth of 0.69 μm in 14 days of incubation. Although this was quite small, it indicated that 2707 HDSS was not completely immune to MIC by the P. aeruginosa biofilm.

The cost of corrosion in China

Corrosion is a ubiquitous and costly problem for a variety of industries. Understanding and reducing the cost of corrosion remain primary interests for corrosion professionals and relevant asset owners. The present study summarises the findings that arose from the landmark “Study of Corrosion Status and Control Strategies in China”, a key consulting project of the Chinese Academy of Engineering in 2015, which sought to determine the national cost of corrosion and costs associated with representative industries in China. The study estimated that the cost of corrosion in China was approximately 2127.8 billion RMB (~ 310 billion USD), representing about 3.34% of the gross domestic product. The transportation and electronics industries were the two that generated the highest costs among all those surveyed. Based on the survey results, corrosion is a major and significant issue, with several key general strategies to reduce the cost of corrosion also outlined.Economics: What corrosion cost China in 2014It is estimated that the effects of corrosion in China cost approximately

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

310 billion USD in 2014. Corrosion is a costly issue, justifying substantial expenditure into techniques to protect and mitigate susceptible metals from its effects, and research investment. China has seen rapid growth in its economy in recent times, driven in part by investment in industry. In order to understand the monetary impact of corrosion in China, The Chinese Academy of Engineering instigated a nationwide study led by the Institute of Oceanology, Chinese Academy of Sciences. It estimates that approximately

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

310 billion USD was lost to the consequences of corrosion and money spent addressing it in 2014, accounting for 3.34% of GDP. Transportation and electronics industries generated the highest costs. Several recommendations are made, including the need for a government-coordinated national strategy.

Atmospheric corrosion behaviour of pure Al 1060 in tropical marine environment

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.

Preparation of Superhydrophobic Film on Ti Substrate and Its Anticorrosion Property

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.

Failure Mechanisms of the Coating/Metal Interface in Waterborne Coatings: The Effect of Bonding

Abstract In this study, atmospheric corrosion behaviour of pure Al 1060 after 1–48 months of exposure in a tropical marine environment was studied. The corrosion kinetics was evaluated by weight loss measurement and pit depth calculation. The rate controlling steps as well as the effect of the native oxide film and the corrosion product layer on the corrosion process were analysed via electrochemical impendence spectroscopy. The results showed that synergetic effect of the deposition rate of chloride ions and time of wetness resulted in an abnormal increase in weight loss and an obvious fluctuation in corrosion rate. During the initial exposure period, corrosion was controlled by charge transfer process attributed to the limited corrosion area. With the increasing exposure duration, the rate controlling step was changed to diffusion due to the barrier effect of the corrosion products. Simultaneously, initiation of the new corrosion areas and the growth of the stable pits dominated the corrosion process during this period, resulting in a lower charge transfer resistance, a larger pit depth and a bigger corrosion area.

Effect of Zinc Phosphate on the Corrosion Behavior of Waterborne Acrylic Coating/Metal Interface

Superhydrophobic films were fabricated on a titanium substrate with or without anodizing by using a self-assembling method. Firstly, the pretreatments of mechanical polishing/anodizing or mechanical polishing only were conducted, respectively. Subsequently, the preparation of polydopamine film layer, deposition of nano-silver particles, and post modification of 1H,1H,2H,2H-perfluorodecanethiol were performed on the surface of the pretreated substrate. The surface morphologies, compositions, wettability, and corrosion resistance of the films were investigated with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), water contact angle measurements, and electrochemical tests, respectively. Meanwhile, the effect of the deposition time in the silver nitrate solution on the hydrophobicity of the specimen surface was investigated. The result showed that with the increase of deposition time, the hydrophobic property enhanced gradually. The surface deposited for 7 h exhibited an optimum hydrophobic effect, which was characterized with a large water contact angle (WCA) of 154°, and the surface was rather rough and covered by a relatively uniform layer of micro-nano silver particles. The excellent hydrophobicity was attributed to a rough stratified microstructure along with the low surface energy. The electrochemical measurements showed that the existence of the superhydrophobic film can effectively enhance the corrosion resistance of Ti samples.