Electrochemical Pourbaix diagrams of NiTi alloys from first-principles calculations and experimental aqueous states

Abstract Pourbaix diagrams (electrode potential-pH diagrams) for pure metals systems are studied completely, whereas researches on diagrams for binary or ternary alloys systems are lagging behind. In this work, we provide a complete procedure for simulations of Pourbaix diagrams of binary and multielement systems. With this scheme, Pourbaix diagrams of Ni Ti alloys with different Ni/Ti molar ratios in aqueous solutions at 25 °C have been constructed based on first-principles chemical potentials of solids and experimental chemical potentials of ions. The corrosion behaviors of different Ni Ti alloys including NiTi, Ti 2 Ni, and Ni 3 Ti are discussed and compared based on the obtained Pourbaix diagrams. The corrosion resistance of Ti 2 Ni is comparable to or even better than that of NiTi while the corrosion resistance of Ni 3 Ti is worse than that of NiTi. In addition, the electrochemical corrosion behaviors of NiTi alloys under Ti-rich and Ni-rich conditions are also investigated; it is found that the precipitations of Ti 2 Ni in Ti-rich NiTi alloys and Ni 3 Ti in Ni-rich NiTi alloys deteriorate the pitting corrosion resistance.