Effect of spray temperature on microstructure and corrosion resistance of cold-sprayed zinc coatings

Abstract

Pure zinc (Zn) coatings were prepared on gray cast iron surfaces by cold spray (CS) to improve their corrosion resistance. The effects of spray temperature on deposition behavior, microstructural characteristics and corrosion performance of Zn coatings were investigated. Higher gas temperatures significantly improved coating thickness and deposition efficiency, yielding dense cold-sprayed Zn coatings with porosity below 1%. The increasing temperature also promoted structural homogeneity and reduced the average grain size to 0.79 μm through localized dynamic recrystallization by severe plastic deformation during CS. Surface wettability analysis revealed that Zn coatings exhibited a hydrophobic nature, with water contact angles exceeding 90°, significantly higher than that of the corroded and hydrophilic cast iron substrate. Electrochemical tests confirmed that the corrosion current density of Zn coatings was two orders of magnitude lower than that of corroded cast iron substrate, demonstrating significantly improved corrosion resistance. Salt spray corrosion testing showed that increasing the spraying temperature promoted the development of a denser and more protective corrosion-product layer, accompanied by lower surface cracking and roughness and increased formation of Zn 5 (OH) 8 Cl 2 ·H 2 O. Cold-sprayed Zn coatings can offer a low-temperature, high-performance solution for corrosion protection of cast iron, showing great promise for extending the service life of iron relics.