ON THE DISTRIBUTION OF NI3S2 IN CORROSION LAYERS OF NIO-NI3S2

Qualitative studies have been made of the interfacial tension between Ni3+/-xS2 and different oxides (NiO, CoO, and feldspar). The results suggest reasons why Ni3+/-xS2 is distributed as an interconnected network along NiO grains in rapidly growing scales formed during reaction of nickel with SO2 and SO2 + O-2 at temperatures from about 550 to 850 degrees C. In the system NiO-Ni3+/-xS2 interfacial energies may stabilize a network of sulfide along edges of NiO grains. Ni3+/-xS2 does not wet the silicate material (feldspar), and this is consistent with previous interpretations that silicates formed by segregation of silicon to NiO interfaces disrupt the sulfide network in scales and thereby provide improved corrosion resistance.