Effect of rare earth oxide (Pr₄O₇) second phase and fine grain on the corrosion behavior of Ti-0.3Mo-0.8Ni

The effect of grain refinement and second phase (Pr₄O₇) on the corrosion mechanism of the Ti-0.3Mo-0.8Ni was studied. The Pr₄O₇ nanophases are distributed in the α/β phase boundaries and the β phases (Pr ≤ 0.5 wt. %). Most of the Pr₄O₇ phases are distributed at the boundaries (Pr ≥ 1 wt. %). The Pr element refines the primary β grains. With the increment of Pr content, the passivation film becomes more stable, denser and thicker, which prolongs the decrease time of OCP, increases the corrosion potential and reduces the corrosion tendency. After the passivation film ruptures, the Pr₄O₇ aggravates the galvanic corrosion.