A scientific research team from Sun Yat-sen University (SYU) (Guangzhou, Guandong, China) has developed an epoxy-based coating with a thickness of about 200 microns (7.9 mils) with iron oxide black (Fe3O4) nanoparticles and tetradecanol that exhibited self-healing properties under solar irradiation. This self-healing coating (SHC) is able to protect underlying carbon steel substates from erosion and solves a key problem common to organic coatings: microcracks that form under different natural conditions, thus allowing water and other corrosive media to penetrate.
The study was recently published in Frontiers of Chemical Science and Engineering.
Metal materials directly exposed to air, water, or other corrosive media are prone to damage due to various physical and chemical changes, resulting in resource waste and environmental problems. A protective layer can effectively slow down the corrosion of the matrix material by isolating the metal from the environmental medium, and its compactness and corrosion resistance are two key factors for the final protective effect.
SHC is a new type of coating system with an extended life expectancy that repairs microcracks or damage to form a repairable physical barrier. Although such coatings can be applied in several ways, including external repair, adding corrosion inhibitors, or using polymer resin and thermoplastic materials, UV irradiation and high-temperature conditions are needed to include the necessary chemical reactions. Thus, SYU researchers looked to develop a SHC that could activate under milder conditions.
They found that their SHC could be heated to 70 °C (158 °F) under simulated solar irradiation due to the photothermal effect of Fe3O4 nanoparticles, which greatly exceed the melting point of tetradecanol at 37.6 °C (99.7 °F). Perforations and scratches caused by scalpels scraping the coating surface were repaired after being irradiated for three minutes. The coating’s wettability was also shown to increase with the addition of tetradecanol. To further confirm the performance of the SHC, the researchers conducted the scratch-heal experiment in a natural outdoor environment and achieved ideal results.
The efficiency of the SHC’s corrosion protection properties on metal substrates can be maintained above 99 percent regardless of repair. It can effectively prevent the infiltration of oxygen, water, and chloride, and shows good stability and protective performance even after immersion in a 3.5 wt% sodium chloride solution for 168 hours.
Source: EurekAlert!, www.eurekalert.org.