New highly corrosion-resistant alloys

Iron alloys are widely used in the industry. Corrosion is a process as an effect of which oxidation of metal in weather conditions occurs, which results in the formation of defects in the material and deposition of metal oxides on its surface. The yearly cost of corrosion is 3-4% of GDP of all industrialised countries. For this reason there is a constant, intensive search for corrosion preventing solutions.

Iron alloys with chromium and silicon demonstrate good anti-corrosion properties. A serious restriction is the amount of added doping – chrome creates intermetallic bonds while silicon increases the brittleness of the material. The publication describes obtaining Fe-Cr and Fe-Cr-Si alloys using oxygen-induced surface segregation of chromium and silicon molecules and presents the resistance of such materials to high-temperature corrosion. The alloys mentioned self-organise in ultra-high vacuum such that the Cr and Si atoms migrate to the surface layer while the iron atoms remain in the volumetric layer. This means that as a result of annealing in atmospheric conditions in the first place oxides of chromium and silicons are formed, while the degree of iron oxidation does not change.

The graph presents spectra using the transmission Mossbauer spectroscopy, for 90% Fe- 5% Cr – 5% Si alloys obtained by arc furnace smelting method. The alloy marked as „-1270K/2h” was additionally annealed at 1270K for 2h in vacuum. The absence of peaks from iron oxides in the region above 7 mm/s and below -7 mm/s after oxidation at 870K indicates that these alloys are highly resistant to corrosion.