Effect of nickel ion from autoclave material on oxidation behaviour of 304 stainless steel in oxygenated high temperature water

Characteristics of the oxide films formed on 304 stainless steel exposed to 290 °C oxygenated water in a nickel-lined autoclave were examined. The oxides evolve from dominating irregularly shaped hematite to faceted spinels with increasing immersion time. The surface layer of oxide film is first Cr-enriched and then Ni-enriched as immersion time increases. The oxides nucleate by solid-state reactions with selective dissolution of Fe and Ni, and then grow up through precipitation of cations from solution. Nickel ions dissolved from the nickel lining could promote the stability of NiFe2O4 spinel and influence the oxidation behaviour of 304 stainless steel significantly.

Research highlights
► Oxides formed evolve from dominating hematite to spinel as immersion time extends.
► Oxides nucleate by solid-state reactions and then develop through precipitation.
► Ni2+ can stabilize NiFe2O4 and influence the oxidation behaviour of 304 SS notably.