Effect of Graphene Nanoplatelets on the Corrosion Resistance of GNPs/AlSi10Mg Composites Fabricated by Selective Laser Melting

Graphene nanoplatelets (GNPs)-reinforced AlSi10Mg composites were fabricated by selective laser melting (SLM), and their corrosion resistance was systematically investigated as a function of GNPs content (0, 0.1, 0.3, and 0.5 wt.%) and corrosion duration. In the short term (≤30 days), the corrosion resistance followed the order: 0.1 wt.% GNPs/AlSi10Mg > 0.3 wt.% GNPs/AlSi10Mg > 0.5 wt.% GNPs/AlSi10Mg > AlSi10Mg. The 0.1 wt.% composite exhibited the best performance, attributed to the uniform dispersion of GNPs that filled micropores and microcracks to form a physical barrier against corrosive ions, along with favorable interfacial bonding that hindered crack growth and reduced corrosion pathways. After 60 days of exposure, however, the ranking reversed to: AlSi10Mg > 0.1 wt.% GNPs/AlSi10Mg > 0.3 wt.% GNPs/AlSi10Mg > 0.5 wt.% GNPs/AlSi10Mg. EIS analysis revealed a porous electrode behavior in the low-frequency response, captured by the constant phase element in the equivalent circuit. The long-term deterioration arose from the gradual penetration of corrosive media through micropores and microcracks, which triggered galvanic corrosion between GNPs and the matrix and rendered the barrier effect ineffective. These findings demonstrate that GNPs addition increases both the number and the total area of cathodic sites in the matrix alloy, thereby accelerating corrosion under prolonged exposure. In essence, GNPs serve as a protective barrier in the short term but transition to corrosion accelerators under long-term exposure.