Microstructure and corrosion behavior of cold sprayed SiCp/Al 5056 composite coatings

Al 5056 composite coatings reinforced with silicon carbide (SiC) particles were deposited by cold spraying. The influence of fraction of ceramic particles on microstructure and corrosion behavior was evaluated. The results show that the addition of SiC particles yields coatings with lower porosity than Al 5056 coating. Quantitative analysis of 3-D optical microscopy images reveals that the maximum size of the embedded pores increases with the fraction of SiC particles. The corrosion performances of coatings were evaluated by open circuit potential measurements and potentiodynamic polarization scans in 0.1 M sodium sulfate solution with pH fixed at 11.5. The OCP values of coatings were much lower compared to pure Al plate. Compared to pure Al plate, the anodic parts of the polarization curves of the coatings show a similar trend; however, the current densities of the coatings evaluated at an overpotential value of + 600 mV (Ioverp) were higher. The addition of SiC particles reduced Ioverp in comparison with Al 5056 coating. Nevertheless, the volume fraction of SiC in feedstock has no significant effect on the anodic polarization behavior. Since all the coatings are dense with a porosity lower than 2.5% and containing no interconnected porosity, thickness and porosity did not affect the corrosion behavior.