Multilayer Coating Enhances Steel's Corrosion Resistance

Multilayered Coating Enhances Steel's Corrosion Resistance Steel is one of the most durable materials known to mankind. When galvanized with zinc (Zn), it becomes more resistant to corrosion. This makes it an economical choice for use in construction and infrastructure. Over the past decade, zinc reserves have declined significantly, forcing us to use zinc alloys. Magnesium (Mg) is the most commonly used alloy mineral and, when used in small quantities, can increase zinc's corrosive resistance. Professor Myeong-Hoon Lee, Head of the Center for Surface Corrosion Control Engineering at Korea Maritime and Ocean University, and his colleagues proposed a new coating for steel that promises to extend service life. Prof. Lee explains: "During my time serving in the navy, I noticed numerous corroded machines. That's why I embarked on this research with the hope of producing better corrosion-resistant steel. The development of high corrosion-resistant materials is necessary to survive in harsh environments. Steel is such a material, and extending its service life makes steel more sustainable." The study was published in the journal Corrosion Science. The proposed multilayered coating consists of three layers produced using physical vapor deposition (PVD). A Zn-Mg layer is sandwiched between two Zn layers. The upper Zn layer protects the Zn-Mg layer from contact with the corrosive environment. The lower Zn layer serves as the final line of defense for the steel. To test the corrosion resistance of this modified steel, two samples were prepared, one containing 10% Mg and the other 25% Mg. The team found that rust signs appeared at 208 hours and 408 hours for the 10% and 25% compositions, respectively, compared to 96/120 hours for conventional Zn coatings. Subsequently, they compared the corrosion resistance of the two compositions. They found that the 25% composition had higher resistance to rusting than the 10% composition. This contradicted earlier reports suggesting that Mg content higher than 8% reduced steel's corrosion resistance. The scientists attributed this contradictory finding to the presence of the upper zinc layer, which made it possible to increase the Mg content in the Zn-Mg layer. Lee states: "The multilayered coating on steel makes it extremely stable, economical and durable, making it an ideal choice for use in harsh environments."   Academic Reference: Jae-Hyeok Park et al, Effect of Zn-Mg interlayer on the corrosion resistance of multilayer Zn-based coating fabricated by physical vapor deposition process, Corrosion Science (2022). DOI: 10.1016/j.corsci.2022.110330 Source