The oxidation behavior of alloy 690 exposed to high-temperature and high-pressure steam and water at 280 ℃ for 1 h was investigated by scanning electron microscopy(SEM),atomic force microscopy(AFM) and X-ray photoelectron spectroscopy(XPS).In high-temperature and high-pressure steam,the oxide film is composed of an outermost Ni-rich hydroxides layer,an intermediate layer of hydroxides and oxides enriched in Cr,an inner oxide layer.The film formed in high-temperature water is similar to that in steam,except for missing the Ni-rich hydroxides layer.Samples with different surface finishes(electropolished,mechanically polished,ground,and as-received) were prepared for comparison.A general increase of the oxide thickness with the degree of surface roughness is observed.The equivalent oxide thicknesses lie in the range of 100-200 nm for the as-received samples,150-250 nm for the samples ground to 400# and 10-20 nm for the samples ground to 1500#,mechanically polished,and electropolished. The oxidation behavior of alloy 690 exposed to high-temperature and high-pressure steam and water at 280 ° C for 1 h was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). In high-temperature and high-pressure steam, the oxide film is composed of an outermost Ni-rich hydroxides layer, an intermediate layer of hydroxides and oxides enriched in Cr, an inner oxide layer. The film formed in high-temperature water is similar to that in steam, except for missing the Ni-rich hydroxides layer. Samples with different surface finishes (electropolished, mechanically polished, ground, and as-received) were prepared for comparison. A general increase of the oxide thickness with the degree of surface roughness is observed. The equivalent oxide thicknesses lie in the range of 100-200 nm for the as-received samples, 150-250 nm for the samples ground to 400 # and 10-20 nm for the samples ground to 1500 #, well polished , and electropolished.