Optimizing SiC Content for Enhanced Corrosion Resistance in Al-5%Cu Alloys Fabricated by Powder Metallurgy

Abstract

Aluminum–copper (Al–Cu) alloys reinforced with silicon carbide (SiC) are attractive for marine applications, yet their corrosion behavior is reported inconsistently in the literature: SiC has been described as both a physical barrier and a galvanic catalyst, depending on its content and distribution. To clarify this, the corrosion performance of Al-5%Cu alloys reinforced with 5, 10, and 15 wt% SiC and produced by powder metallurgy was systematically investigated. Corrosion kinetics were evaluated using potentiodynamic and cyclic polarization tests in 3.5 wt% NaCl solution. Microstructural variations and phase composition were examined using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results reveal a non-linear relationship between SiC content and corrosion resistance, with a clear optimum at 10 wt% SiC. Adding 5 wt% SiC reduced the corrosion rate from 0.88 ± 0.05 mm/yr (unreinforced alloy) to 0.028 ± 0.002 mm/yr, but pitting susceptibility was observed. The 10 wt% SiC composite exhibited the lowest corrosion rate (0.011 ± 0.001 mm/yr) and complete suppression of pitting, attributed to uniform SiC distribution and the formation of a stable passive layer. In contrast, at 15 wt% SiC, agglomeration enhanced micro-galvanic coupling and increased the corrosion rate to 0.53 ± 0.03 mm/yr. These findings indicate that 10 wt% SiC is the critical reinforcement level for maximizing corrosion resistance in Al-5%Cu/SiC composites produced by powder metallurgy, providing guidance for material development in chloride-rich environments.