Microstructure and Surface Degradation of Al-Al9Co2-Al13Co4 Composites in HCl Medium

Abstract

The Al-Co alloys corrosion resistance of various Co compositions (0.5-5 at.% Co) at different sintering times (4 h, 8 h, 24 h, 48 h, and 72 h) for 25°C in (1M) hydrochloric acid electrolyte was studied by employing the electrochemical impedance spectroscopy (EIS) and the tafel polarization. Raman technique was used to identify the surface film of aluminum and its alloys, and scanning electron microscope (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) was used to determine the microstructure of the materials. In comparison to undoped aluminum, the Al-5 at.% Co material sintered at forty-eight hours exhibited outstanding corrosion performance. Pitting is discernible in the microstructure of sintered materials, particularly within the Al9Co2 phase. This phase exhibits faster corrosion compared to other intermetallic compounds such as Al13Co4. In terms of crystal structure and chemical composition of the dopant, the Al-Co intermetallic compounds are classed as a function of their relative nobility.