<p>The effect of surface roughness on the oxidation behavior of the FBB8 (Fe-9.96Ni-10.7Cr-6.49Al-0.25Zr-3.49Mo-0.0094B) alloy in air at 900&#xa0;°C was investigated in this study. The results indicated that the parabolic rate constants (<i>K</i>_p) for the samples with arithmetic roughness average (Ra) values of 0.2&#xa0;µm, 1.2&#xa0;µm and 2.1&#xa0;µm were 3.68 × 10⁻¹³ g²·cm⁻⁴·s⁻¹, 5.26 × 10⁻¹³ g²·cm⁻⁴&#xa0;s⁻¹, and 7.91 × 10⁻¹³ g²·cm⁻⁴·s⁻¹, respectively. This positive correlation indicates that increased surface roughness accelerates mass gain during the early oxidation stage. When the substrate Al content was depleted below a critical level, the B2 phase acted as an “aluminum reservoir” to replenish consumed Al. The sample with a Ra value of 0.2&#xa0;µm exhibited discontinuous external oxide scale and severe internal oxidation, caused by insufficient nucleation sites. In contrast, the ground sample with a Ra value of 2.1&#xa0;µm reduced internal oxidation by introducing a stress-induced scale at the surface that promoted outward diffusion of Al. The influence of surface roughness on the oxidation behavior of FBB8 alloy was elucidated in this study through its effects on element diffusion and oxide film formation, offering key insights for optimizing surface treatment processes.</p>