Electrochemical corrosion behavior of the cobalt modified aluminide coating in 3.5 wt% NaCl solutions

Abstract

In this paper, we achieved the Co modified aluminide coating on nickel base superalloys by pack cementation process. The corrosion currents ( i corr ) of coated and uncoated substrate after 1 h of immersion tested by potentiodynamic polarization in 3.5 wt% NaCl solutions are 9.73b × 10 −7 A/cm 2 and 1.31 × 10 −6 A/cm 2 , respectively. With the immersion time extension, the i corr of the coating decreases and the values of |Z| by EIS increase, indicating that the electrochemical reaction rate of the coating becomes slower. The coating presents good corrosion resistance due to the Al 2 O 3 formed on the surface. • Corrosion behavior of Co modified aluminide coating on DZ125 superalloy was studied. • Corrosion current density in NaCl solution decreased with the immersion time. • The impedance |Z| of the coating in NaCl solution increased with the immersion time. • Good corrosion resistance was attributed to the formation of Al 2 O 3 on the coating.