Oxide formation mechanism of a corrosion-resistant CZ1 zirconium alloy

•CZ1 alloy has superior corrosion resistance beyond Zr-4 and improved Zr-4 alloys.•Lowering Sn and Nb contents give rise to the less tetragonal ZrO2 phase in oxides.•Low-density lateral cracks reduce the diffusion route for oxidating species.•Second-phase particles relieve the metal-to-oxide transformation-induced stresses.•Tailoring microstructure and microchemistry enables the deceleration of corrosion.