Aqueous corrosion and oxidation behavior of the Pd-FeCr surface alloys produced by ion beam mixing

Singly charged argon ions are used to intermix sputter-deposited Pd thin films of various thicknesses with the Fe-24Cr substrate alloy. The corrision behavior of these ion beam mixed alloys was studied electrochemically in 0.5M HCI solution (25°C). The oxidation behavior of the same alloys in air at 400°C was studied using Auger depth profiling techniques. Electrochemical measurements indicate that the ion mixed 200 Å Pd/Fe-24Cr alloy passivates for a very short period of time (40 min), after which a negative shift in the electrode potential to the active region occurs due to the dissolution of the thin Pd-enriched surface layer. Prolonged corrosion protection against active dissolution in 0.5M HC1 solution can be achieved in the ion mixed 400 Å Pd/Fe-24Cr and 600 Å Pd/Fe-24Cr surface alloys due to the formation of a thicker Pd-enriched surface layer containing Fe-Cr. The Auger depth profiles revealed that a thick chromium oxide layer tended to form with and on the thicker Pd-enriched surface alloy in air at 400°C. © 1991.