Influence of dissolved oxygen concentration on the oxide film formed on 304 stainless steel in high temperature water

Characteristics of the oxide films formed on 304 stainless steel under different dissolved oxygen (DO) concentrations in 290 °C water were investigated. Less hematite and more spinel oxides form on fresh sample as DO decreases. Meanwhile, relative Cr content in the film increases. Spinel develops on the film preformed under 3 ppm DO when it was further immersed under DO below 5 ppb while the preformed hematite degrades. The spinel preformed under DO below 5 ppb still grows up when further immersed under 3 ppm DO while the base layer becomes more porous due to dissolution of Cr.

► Less hematite and more spinel oxides form on fresh SS sample as DO decreases.
► Spinel grows while hematite degrades on film preformed under 3 ppm DO as DO drops.
► Spinel still dominates on film preformed under DO below 5 ppb as DO rises to 3 ppm.
► The base layer preformed under DO below 5 ppb becomes porous as DO rises to 3 ppm.