Corrosion behavior of cold sprayed 7075Al composite coating reinforced with TiB2 nanoparticles

Abstract

Cold spray (CS), as a novel surface treatment technique, has been widely used for repairing damaged components and as protecting coatings, especially for the applications of aircraft and marine components. To further improve the mechanical properties, while maintaining the corrosion resistance of pure Al and Al alloy coatings, ceramic particles are commonly added into the Al matrix to produce particle-strengthened Al matrix composite (P-AMC) coatings. In this study, dense 7075Al composite coatings reinforced with uniformly distributed in-situ TiB 2 nanoparticles (hereafter named TiB 2 /7075Al) were successfully produced by CS using a gas-atomized composite powder and the propulsive gases of air and helium. Following this, the corrosion behavior of the cold sprayed (CSed) TiB 2 /7075Al composites was investigated using Tafel polarization, electrochemical impedance, spectroscopy, and immersion tests in 0.1 M and 0.6 M NaCl solutions, and were compared to those of the CSed pure 7075Al coating and bulk 7075Al-T6 material. Electrochemical tests revealed that the composite coating exhibits a higher corrosion rate than the pure 7075Al coating, primarily caused by a galvanic coupling between TiB 2 nanoparticles and the more active Al matrix. Compared to the air-processed coatings, the He-processed ones exhibit higher densities of defects, like dislocations, and precipitates due to larger plastic deformation of the sprayed particles, which result in more active sites for corrosion and thus lower corrosion resistance. Low-temperature annealing treatment (230 °C/6h) reduces these defects to increase the corrosion resistance of the CSed coatings. Comparatively, high-temperature annealing treatment (412 ℃/4h) results in coarsening of precipitates and grain growth to increase the corrosion rate of the coatings. Corrosion mechanisms of the CSed and annealed composite coatings related to the microstructure evolution were investigated in detail.

Al matrix composites fabricated by solid-state cold spray deposition: A critical review

“…Electrochemical tests revealed that the TiB2/7075Al composite coating exhibited a higher corrosion rate than the pure 7075Al coating due to a galvanic coupling between TiB2 nanoparticles and the more active Al matrix. Therefore, the corrosion property of the CS AMCs was found closely connected to the porosity, microstructures, interactions between the Al matrix and the reinforcement particles, and the type of reinforcement particles [129].…”

“…In general, SiC and Al2O3 particles are the two most commonly used reinforcements for anti-corrosion AMC coatings due to their neutral property. Xie et al [129] investigated the corrosion behavior of the cold sprayed TiB2/7075Al composite coating. Electrochemical tests revealed that the TiB2/7075Al composite coating exhibited a higher corrosion rate than the pure 7075Al coating due to a galvanic coupling between TiB2 nanoparticles and the more active Al matrix.…”

Influence of processing conditions on the mechanical, tribological and fatigue performance of cold spray coating: a review

“…Hence, corrosion prevention for Mg alloy needs advanced and high-efficiency techniques. By depositing cold spray coating, the fatigue resistance can be enhanced’ [254], but in some cases cold spray coating does not have an effective enhancement in resistance against corrosion fatigue [251,255]. As per the research done by various authors on the corrosion of magnesium, the main corrosion type is pitting corrosion [256].…”

A Repair Method for Damage in Aluminum Alloy Structures with the Cold Spray Process

“…There were no visible pores and cracks that penetrated the entire cross-section. Thus, it was not easy for a corrosive medium to directly infiltrate into the inner substrate [21,22]. In addition, a boundary between the repaired areas and the substrate was apparent.…”