Enhanced corrosion on zirconium-base alloys in proximity to other metals, the shadow effect, has been observed since the 1960s. Possible remedies against shadow corrosion have been investigated. The effect of 0.1- to 9-μm-thick zirconia (ZrO₂) coatings of Inconel X-750 spacer cells on shadow corrosion of fully recrystallized LK3 Zircaloy-2 boiling water reactor cladding is investigated in this paper. The coatings were produced by a combination of two solution-based techniques, where (i) a nanoparticle-based route was used to build thick coatings, and (ii) a modified alkoxide route was used to build thinner dense coatings. Twenty-one spacer cells, sixteen with ZrO₂ coating and five uncoated reference spacer cells, were inserted along the central instrumentation tube in an instrumented fuel assembly in a boiling water reactor loop in the Halden test reactor. The instrumented fuel assembly was subsequently operated at high power for 149 days. The investigations revealed that shadow corrosion occurred on the Zircaloy-2 tubing under all spacer cells. The significance of the shadow was strongly affected by the thickness of the ZrO₂ coating from the spacer cells. Small effects were observed for coating thicknesses below 2.5 μm, while thicknesses of 4.5 and 9 μm reduced the shadow corrosion up to 42 and 26%, respectively.