The reaction of preoxidized nickel in SO2 at high temperatures

The reaction between preoxidized nickel and SO₂ was studied at 800–1000° C. The experimental methods consisted of thermogravimetry, metallography, scanning electron microscopy, and electron microprobe analysis. Sulfur accumulates in the surface layer of the metal during the SO₂ exposure. It is concluded that this is due to transport of SO₂ through the oxide scale. This leads in turn to formation of a Ni-S liquid solution which eventually ruptures the scale and causes an accelerated, breakaway reaction behavior. The induction period for the accelerated reaction increases with increased preoxidation and furthermore is influenced greatly by the microstructure of the oxide scale.