Hot Corrosion Behavior of Ni-Base Alloys Coated with Salt Film of 75%Na2SO4+25%NaCl at 900 °C

Abstract

Abstract The hot corrosion behaviors of pure Ni, Ni-10Cr alloy and Ni-10Cr-5Al alloy (mass fractions, %, similarly hereinafter) coated with salt film of 75%Na 2 SO 4 +25%NaCl (mass fraction) were investigated at 900 °C in air. Results show that the corrosion kinetic curve of Ni-10Cr approximately follows the parabolic rate law while the corrosion kinetic curves of Ni and Ni-10Cr-5Al alloy follow the parabolic rate low by stages. The corrosion mass gain of Ni-10Cr is minimum, the one of Ni-10Cr-5Al comes next and that of pure Ni is maximum. The corrosion products of Ni-10Cr-5Al can be divided into three layers, of which the outermost layer is mainly composed of NiO, the intermediate layer consists of Cr 2 O 3 and Al 2 O 3 , and the internal corrosion zone contains a small amount of Cr 2 S 3 and Al 2 S 3 . For Ni-10Cr alloy, the corrosion products consist of three layers, the outermost layer of NiO, the intermediate layer of noncontinuous Cr 2 O 3 and the internal corrosion zone with a small amount of Cr 2 S 3 . The corrosion scales of Ni-10Cr-5Al and Ni-10Cr are both loose and porous due to the existence of NaCl.