Particle-particle interface corrosion of cold sprayed copper in dilute nitric acid solutions: geometry-controlled corrosion mechanism

We report here the mechanism of accelerated corrosion observed at the particle-particle interfaces (PPIs) of cold sprayed (CS) Cu exposed to dilute nitric acid. PPI corrosion is triggered by the oxide inclusions present along the PPIs. The accelerated corrosion at PPIs results from the combined effects of confined geometry and catalytic reactions, which involve the electrochemical dissolution of Cu and reduction of NO3−. Gas bubbles composed of N2O and NO form continually during PPI corrosion, indicating the ongoing reduction of NO3−. Annealing the CS Cu at 600 °C causes the oxide inclusions to coalesce, thereby breaking the interconnected oxide inclusion network. Consequently, the propagation of PPI corrosion is impeded. This work demonstrates how geometrical factors can determine the corrosion process and emphasizes the role of microstructural defects in the corrosion properties of additively manufactured materials.