Effect of Fe addition on corrosion behavior of Ni–xFe–5Cr alloys at 570°C in air containing salt vapor

Abstract

The high-temperature corrosion behavior of Ni–xFe–5Cr alloys (x = 0, 10, or 30 wt.%) was investigated in air containing alkali salt vapor at 570°C to clarify the effect of Fe on the corrosion resistance. Fe addition to Ni–5Cr was found to improve the corrosion resistance under the present conditions. In the case of Ni–5Cr, NiCl₂ was formed beneath the NiO scale during the initial stage of corrosion, and it grew thicker over time and then evaporated. The formation and evaporation of NiCl₂ resulted in a porous scale that underwent spallation resulting in mass loss. In the Fe-containing alloys, (Fe, Ni, Cr)₃O₄ spinel and Fe₃O₄ decreased the partial pressures of oxygen and chlorine and thus prevented the generation of NiO and NiCl₂, leading to superior corrosion resistance compared with Ni–5Cr.