Researchers Analyze Corrosion to Design Better Protective Thin Films for Metals

Researchers from University of Wisconsin-Madison analyzed oxide films at the atomic level and to decipher the arrangement of atoms in the oxides

Corrosion of metals is normally protected by naturally forming and super-thin oxide films. Conventionally, these protective films are considered as simple oxides of well-anticipated compounds. However, now a team of researchers from Northwestern University, the University of Virginia, and the University of Wisconsin-Madison demonstrated novel insights into these oxide films. The team used state-of-the-art experimental techniques and theoretical modeling to analyze oxide films at the atomic level and to decipher the arrangement of atoms in the oxides. The team found that the protective films develop new structures and compositions that depend on the speed of the growth of the oxide film. The findings published in the journal Physical Review Letters on October 04, 2018, could facilitate development of effective oxide films.

The researchers analyzed the oxides that form on alloys composed of nickel and chromium. These oxides are often used for applications with presence of water. Moreover, these oxides work when hot and resist corrosion in the mouth, owing to formation of an oxide of chromium. It was previously assumed that nickel formed a separate oxide, however, the researchers found that the oxide contained a very large number of nickel atoms along with chromium and oxygen. This is owing to the inability of nickel atoms to escape from the oxide. The fraction of nickel atoms that are captured depends upon the speed of growth of the oxide. When the oxide grows slowly, nickel atoms can escape, however, they get trapped when oxide grows very fast. This phenomenon occurs both when the metals are reacting with oxygen from the air at high temperatures and when they are reacting with water. According to the researchers, the atoms that are captured in the oxide change several of the properties. The findings suggested that it is possible to deliberately trap atoms into these oxides in new ways to change their behavior.