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

The high‐temperature corrosion behavior of Ni– x Fe–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, NiCl 2 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 NiCl 2 resulted in a porous scale that underwent spallation resulting in mass loss. In the Fe‐containing alloys, (Fe, Ni, Cr) 3 O 4 spinel and Fe 3 O 4 decreased the partial pressures of oxygen and chlorine and thus prevented the generation of NiO and NiCl 2 , leading to superior corrosion resistance compared with Ni–5Cr.