Effect of Chromium Addition on the Corrosion Resistance of Ti-Ni-(Pd, Ru) Alloy

General corrosion and crevice corrosion behaviors of titanium alloys, Ti-Ni-(Pd, Ru)-Cr and Ti-Cr have been investigat-ed in comparison with the unalloyed titanium. The specimens of the alloyed and unalloyed titanium were subjected to conventional immersion test in hydrochloric acid solutions and a concentrated chloride solution at elevated tempera-tures. Electrochemical properties of the alloys were also measured in order to understand the effect of chromium addition on the corrosion behaviors. The results have indicated that an excellent improvement in general corrosion and crevice corrosion resistance is attained by chromium addition with nickel, palladium and ruthenium. However, a single addition of chromium deteriorates the corrosion resistance of titanium in hydrochloric acid solutions. The corrosion kinetics for the alloys is discussed in terms of the compositional change on the corroded surface during the corrosion process. An excellent corrosion resistance of Ti-Ni-(Pd, Ru)-Cr alloy is considered to be originated from enrichment of palladium and ruthenium, which is promoted by chromium addition.