| Summary: | Cold spraying was used to prepare Al/Al<sub>2</sub>O<sub>3</sub> composite coatings. The Al<sub>2</sub>O<sub>3</sub> content was controlled to increase the mechanical property and corrosion resistance of the composite coating. The inclusion of Al<sub>2</sub>O<sub>3</sub> particles results in considerable plastic deformation of Al particles and grain size refinement in the coating. Additionally, the coating’s surface roughness decreased from 24.63 μm to 9.02 μm, and the porosity decreased from 6.34% to 2.07%. The increase in microhardness of the composite coatings was attributed to the combined effect of residual compressive stress, second phase strengthening of Al<sub>2</sub>O<sub>3</sub>, and plastic hardening of Al particles. The electrochemical test results indicate that the mass fractions of Al<sub>2</sub>O<sub>3</sub> significantly affected the corrosion resistance of the Al/Al<sub>2</sub>O<sub>3</sub> composite coating. Compared to the Al coating, the composite coating exhibited improved corrosion resistance, with a reduction in corrosion current density from 1.09 × 10<sup>−3</sup> A/cm<sup>2</sup> to 2.67 × 10<sup>−6</sup> A/cm<sup>2</sup> and an increase in corrosion potential from −1.57 V to −1.14 V. However, when the alumina particle content exceeded 17.7%, it led to more Al<sub>2</sub>O<sub>3</sub> particle breakage, increasing the weak bonding interfaces in the composite coating, and consequently reducing its corrosion resistance.
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