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CORROSION PROTECTION MECHANISM OF THE INTACT, DAMAGED AND HEALED SHCS CREDIT ZHIFENG LIN, WEIHUA LI

Abstract:
Metal materials directly exposed to air, water or other corrosive media are prone to damaged due to various physical and chemical changes, causing huge resource waste and environmental problem. A protective layer can effectively slow down the corrosion of the matrix material by isolating the metal from environmental medium, and its compactness and corrosion resistance are two key factors for the final protective effect.

A sunlight-driven “self-healing” anti-corrosion coating

Beijing, China | Posted on May 27th, 2022

Compared with inorganic coatings such as enamel and ceramics, organic coatings are more likely to form denser cover on the metal surface, with wide range of sources and good corrosion resistance, have been widely used nowadays. But a critical fact is that microcracks are easily to form on the surface of organic coating under different natural application conditions, allowing water and other corrosive media to penetrate.

To solve this problem, the scientific research team of Zhifeng Lin and Weihua Li from Sun Yat-sen University prepared an epoxy-based coating (thickness about 200 μm) with Fe3O4 nanoparticles and tetradecanol which exhibited self-healing ability under solar irradiation and could protect the underlying carbon steel (CS) substrate from erosion. This study has just been published in Frontiers of Chemical Science and Engineering.

Self-healing coating (SHC) is a new type coating which has extended life expectation by repairing microcracks or damage to form a repairable physical barrier, was firstly reported only 20 years ago. Although several ways can be applied to achieve the self-healing coatings, including external repair/corrosion inhibitors addition, polymer resin self-dynamic bonding and thermoplasticity/shape-memory materials usage, UV irradiation or high temperature conditions are necessary to induce chemical reactions, so self-healing coatings achieved under mild conditions are urgently demand.

They found that the SHC coating could be heated to 70 °C in only 200 s under simulated solar irradiation due to the photothermal effect of Fe3O4 nanoparticles, which greatly exceeded the melting point of tetradecanol at 37.6 °C. And the perforations and scratches caused by scalpel on the coating surface were repaired only after the simulated solar irradiating for 3 minutes. Its wettability was also proved to increases with the addition ratio of tetradecanol, attributed to a large number of polar hydroxyl groups on it. To testify the performance of SHC coating in real natural environment, researchers took the coating scratch-heal experiment under natural outdoor light as well and finally achieved ideal results.

The corrosion protection efficiency of SHC coating on the underlying metal substrate is verified can be maintained above 99% regardless of the repair. It can effectively prevent the infiltration of O2, H2O, and Cl–, and shows good stability and protective performance even after immersion in 3.5 wt% NaCl solution for 168 hours.

By selecting appropriate liquefied phase change materials, photothermal particles and mix them with suitable content, scientists achieved a novel self-healing of anti-corrosion coating under sunlight in simple way. The SHC coating possesses good photothermal property and can transform into liquid flow under sunlight to fill the defects. Its impermeability and anti-corrosion property are comparable to commercial coatings, expected to be mass-produced and used for corrosion protection in outdoor facilities.

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About Higher Education Press
Founded in May 1954, Higher Education Press Limited Company (HEP), affiliated with the Ministry of Education, is one of the earliest institutions committed to educational publishing after the establishment of P. R. China in 1949. After striving for six decades, HEP has developed into a major comprehensive publisher, with products in various forms and at different levels. Both for import and export, HEP has been striving to fill in the gap of domestic and foreign markets and meet the demand of global customers by collaborating with more than 200 partners throughout the world and selling products and services in 32 languages globally. Now, HEP ranks among China's top publishers in terms of copyright export volume and the world's top 50 largest publishing enterprises in terms of comprehensive strength.

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About Frontiers of Chemical Science and Engineering

Frontiers of Chemical Science and Engineering presents the latest developments in chemical science and engineering, emphasizing emerging and multidisciplinary fields and international trends in research and development. The journal promotes communication and exchange between scientists all over the world. The contents include original reviews, research papers and short communications. Coverage includes catalysis and reaction engineering, clean energy, functional material, nanotechnology and nanoscience, biomaterials and biotechnology, particle technology and multiphase processing, separation science and technology, sustainable technologies and green processing. The Editors-in-Chief are Academician Jingkang Wang from Tianjin University, Academician Qunji Xue from Ningbo Institute of Industrial Technology and Academician Jiongtian Liu from Zhengzhou University. The journal has been indexed by SCI, Ei, CA, ChemWeb, INSPEC, SCOPUS, Source Journals for Chinese Scientific and Technical Papers and Citations, CSCD, etc.

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