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Though the classical transport theory does not mathematically express the Arrhenius-like relation between Cr-loss flux due to volatilisation and absolute temperature, such relation was experimentally observed for 409L stainless steel exposed at 600–750 °C. Volatilisation calculation in the present cases can be estimated giving such relation because of the nearly linear relation between mass transfer coefficient and temperature. Cr-loss fluxes in O 2 with 20 and 40 % H 2 O are close to or coincided with the fluxes calculated from MnCr 2 O 4 evaporation. Increasing water vapour could enhance volatilisation contributed from the raised CrO 2 (OH) 2 pressure, reduce oxidation rate, and worsen scale adhesion. • 409L stainless steel was assessed at 600–750 °C for SOFC interconnect application. • Flux of Cr loss by volatility related to temperature in the Arrhenius-like form. • Cr-loss flux equation can be simplified resulting in the Arrhenius-like relation. • Water vapour could help reduce oxidation rate with enhanced scale volatilisation. • Water vapour could worsen the scale adhesion. [ABSTRACT FROM AUTHOR]

• A type 430 stainless steel is coated by Mn-Co spinel by a slurry method. • Continuous Cr 2 O 3 formed by pre-oxidation before coating reduces a scaling rate. • Pre-oxidation helps reduce Cr loss by volatilisation. • Coating structure e.g. pore size affects the flux of Cr loss. • Dependence of gas diffusivity on the coating structure is graphically proposed. An AISI 430 stainless steel was coated by Mn-Co spinel using a slurry method. Pre-oxidation before the coating helped reduce the oxidation rate of the coated steel at 800 °C in O 2 -5%H 2 O, relating to the formation of the continuous chromia layer which inhibited the outward diffusion of iron to the coating layer. It also helped reduce the mass flux of Cr loss due to the volatilisation. The combined molecular and Knudsen diffusion of the volatile species through the coating layer was suggested to explain the reduced volatilisation rate of the coated sample with pre-oxidation. [ABSTRACT FROM AUTHOR]

Less mass gain and poorer scale adhesion assessed by the tensile test of the AISI 430 stainless steel exposed to O 2 -40%H 2 O at 800 °C were observed in comparison with the exposure to O 2. The reduced mass gain was partly due to Cr-species volatilisation while the worse scale adhesion related to pores formed at scale/steel interface. The Brouwer diagrams were proposed to help discuss the water vapour effect on altering defect concentrations that could affect the oxidation rate and scale adhesion of the studied steel. • AISI 430 stainless steel was exposed to O 2 -40%H 2 O and O 2 at 800 °C. • The steel oxidised in O 2 -40%H 2 O had less mass gain and poorer scale adhesion. • Cr volatilisation in O 2 -40%H 2 O had significant effect on reducing mass gain. • Pores were observed at the interface between steel and scale formed in O 2 -40%H 2 O. • Brouwer diagrams of Cr, Mn and H interstitials in O 2 -H 2 O were proposed. [ABSTRACT FROM AUTHOR]