Enhanced corrosion resistance of titanium foil from nickel, nickel-molybdenum and palladium surface alloying by high intensity pulsed plasmas

The corrosion resistance of titanium, surface-treated by high intensity, nitrogen-plasma pulses to alloy the surface with nickel, nickel-molybdenum or palladium is determined in 0.1 M H₂SO₄ at 80 °C for immersion times up to 100 h. The purpose of the study is to identify surface treatments that have the potential to extend the life of the titanium foil window used in the clean-up of flue gases, including removal of SO₂, NO_x and volatile organic compounds, employing electron beam technology. The alloy layers, less than 1 μm thick, were produced using either deposition by pulsed erosion or pulsed implantation doping (PID) modes, with various conditions examined for each mode. The results revealed major improvements in the corrosion resistance of titanium, typically by about two orders of magnitude, following the various treatments, which are explained by the promotion of passivity of the titanium associated with a shift in the open-circuit potential. Thus, the open circuit potential of titanium was about −780 mV (SCE), compared with −300 to −250 mV (SCE) for nickel alloying, −130 to 50 mV (SCE) for nickel-molybdenum alloying and 400-470 mV (SCE) for palladium alloying. The PID process tended to result in slightly more positive potentials.