The influence of tin implantation on the oxidation of iron

The high-temperature oxidation of metallic iron implanted with Sn ions at doses between 5 X 10 15 and 5 X 10 16 Sn ions cm-² is studied in the temperature range from 300 to 500 °c. Ion implantation of Sn reduces the oxidation rate constant of iron up to a factor of 10 at all experimental temperatures. The mechanisms that underlie this process are investigated using physical techniques such as Rutherford backscattering of 4He particles, conversion electron Mössbauer scattering of 57Fe and 119Sn and scanning electron microscopy to analyze the surface of the implanted and oxidized samples. The FeSn2 intermetallic phase was formed in the sample implanted at room temperature. This compound is partially decomposed to the FeSn intermetallic and free Sn in solution in iron when the implanted sample is oxidized at 500 °C. Ion implantation produces a surface composition very similar to that obtained with the more conventional methods oftinplating. The observed inhibition of the corrosion is discussed on the basis of this similarity