High temperature oxidation behavior of Ni in an 1%HCl-50%O-2-N-2 atmosphere was examined at 973-1273 K by thermogravimetric technique, XRD and EPMA analyses. Mass loss was observed at all the temperatures and increased with time and with temperature. The consumptions of Ni in 1%HCl were larger than those in 100%O-2. This fact suggests that Ni is acceleratedly corroded in 1%HCl. After the oxidation test, a NiO scale was found on the specimen. Furthermore, it was found that the NiO scale is constructed of some layers and Cl exists around the metal/scale interface in the scale. Evaporation of NiCl2 was identified by analysis of deposits inside the experimental reaction tube. The formation of NiCl2 was also recognized from the fact that total consumption of Ni was larger than consumption of Ni for NiO formation. Namely, the difference of the two consumptions represents Ni consumption for NiCl2 formation. From these results and thermodynamical discussion, it was suggested that the oxidation of Ni in an 1%HCl atmosphere proceeds by alternate reactions of oxidation and chlorination.
