Microstructure characterization and corrosion behavior of cold spray additively repaired titanium for hydrometallurgy applications

Abstract

Cold spray additive repair (CSAR) is a solid-state additive manufacturing approach used to restore the thickness and extend the service life of titanium (Ti) components operating in aggressive hydrometallurgical environments. In this study, high-pressure cold spray deposition was used to restore commercially pure titanium (CP Ti) components by building up a 5 mm thick CP Ti repair layer, and its microstructure and corrosion performance were compared with those of as-received wrought CP Ti in 60 g l−1 H2SO4, 20 g l−1 NaCl, and a mixed H2SO4 and NaCl electrolyte, selected to represent aggressive chemical conditions relevant to nickel laterite high-pressure acid leaching hydrometallurgical processing. Microstructural characterization revealed a dense splat-based architecture with ∼1% porosity. Electrochemical testing demonstrated a strongly electrolyte-dependent corrosion response. In sulfuric acid, the CSAR CP Ti exhibited lower corrosion current density and higher polarization resistance compared with the wrought material. In contrast, in chloride-containing environments, the CSAR material showed increased corrosion current density and reduced impedance response, attributed to inter-splat boundaries and microstructural heterogeneity that facilitate aggressive ion transport and localized film disruption. No crevice corrosion was observed for either material under ASTM G48-11 Method B conditions. The results demonstrate that CSAR is a viable restoration approach for high-value Ti components in acid-dominated hydrometallurgical environments, while highlighting the importance of electrolyte chemistry in governing long-term corrosion performance.