This thesis studied the electrochemical properties of the FeCoNi based alloys, such as FeCoNi, Cr0.5FeCoNi, and CrFeCoNi alloys under as-cast and as-annealed (1000˚C-2hr) states. The results indicated that all the matrix of these alloys were FCC structure. We also observed some HCP-structured precipitates in the matrix of the alloys contented Cr element; and these alloys had precipitation strengthening effect after annealed.Furthermore, these alloys were static immersed into 5M H2SO4 solution by measuring their corrosion rates. And,the polarization curves these alloys were tested under four different temperatures of 1 M H2SO4 solution, 30˚C, 40˚C, 50˚C, and 60˚C. After that, this experiment analyzed corrosion potentials, corrosion currents, and the passive range of potentials. All these results werealso compared with the properties of commercial 304 stainless steel.
After static immersed in the 5M H2SO4 solution, the results indicated thatthe as-annealed alloys containing Cr would be corrodedeasily than the as-cast alloys with same compositions. But the as-cast FeCoNi was worse than as-annealed one because of segregation.The corrosion potentials and currents of these alloys did not change significantly in the H2SO4 solution with different temperatures.However, the currents of passive regions would gradually increase while the temperatures increased.In addition, the passive currents and potentials of as-cast and as-annealed alloys all better than that of commercial 304 stainless steel.
