Zirconium alloys are used as fuel cladding in light water reactors. Surface preparation techniques that might impair oxidation resistance would limit the lifetime of the cladding and therefore prevent higher burn-up of fuels. The work presented here investigates the impact of surface roughness on the oxida-tion kinetics of Zircaloy-4 in 400 ◦C steam for exposures up to 275 days. The work shows well defined differences in oxidation kinetics between sample preparations following ∼84 days oxidation. Scanning electron microscopy (SEM) and image analysis of samples in cross section allows for an assessment of the variation in surface roughness between samples at different stages of oxidation.