The influence of ingot annealing on the corrosion resistance of a PrFeCoBNbP alloy

The influence of the annealing time on the corrosion resistance of a Pr–Fe–Co–B–Nb alloy with the addition of 0.1 wt% P was investigated here using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The cast ingot alloys were annealed at 1100 °C for 10, 15 and 20 h. The specimens were immersed for 30 days in naturally aerated 0.02 M Na₂HPO₄ solution at room temperature, during which period the evolution of the electrochemical behavior was assessed using EIS. The results indicated that the corrosion resistance of the Pr₁₄Fe_balCo₁₆B₆Nb_0.1P_0.25 alloy was related to the annealing time and, hence, to its microstructure. Annealing at 1100 °C for 10 h was insufficient to eliminate the Fe- phase from the alloy microstructure, whereas annealing for 15 and 20 h removed an increasing amount of Fe- phase, thereby increasing the alloy's corrosion resistance.