Pitting Corrosion of Ni3(Si,Ti)+4Al Intermetallic Compound at Various Chloride Concentrations

Abstract

The pitting corrosion of Ni₃(Si,Ti) with 4 at% Al consisting of two regions of a Ni₃(Si,Ti) single-phase of L1₂ structure and two phases of L1₂ and fcc Ni_ss was investigated as function of chloride concentrations by using electrochemical method, scanning electron microscope and energy dispersive X-Ray spectroscopy in neutral sodium chloride solutions at 293 K.  In addition, the pitting corrosion of Ni₃(Si,Ti) and  type C276 alloy were also studied under the same experimental condition for comparison.  The pitting potential obtained for the Ni₃(Si,Ti) with 4 at%Al decreased with increasing chloride concentration.  The specific pitting potential and pitting potential of Ni₃(Si,Ti) with 4at%, Ni₃(Si,Ti) and C276 were the lowest, the moderate and the highest, respectively, which means that the pitting corrosion resistance of Ni₃(Si,Ti) was higher than Ni₃(Si,Ti) with 4at% Al, but lower than that of C276.  A critical chloride concentration of Ni₃(Si,Ti) with 4at% Al was found to be lower than that of Ni₃(Si,Ti).  The Pitting corrosion of Ni₃(Si,Ti) with 4at% Al occurred in the two phase mixture (L1₂ + Ni_ss).