Localized Corrosion of Silicon-Reinforced Aluminum Composites in Na2SO4 Solution

• Published in: ECS transactions 2007-02, Vol.2 (9), p.99-110
• Main Authors: Ding, Hongbo, Hihara, Lloyd H.
• Format: Article
• Language: English
• ISSN: 1938-5862; 1938-6737
• DOI: 10.1149/1.2408932

Localized corrosion formed on an Al-based metal-matrix composite (MMC) reinforced with 40 wt% Si particles in an air-exposed 0.5 M Na2SO4 solution. Scanning vibrating electrode technique revealed that the net currents over the localized corrosion region were cathodic. Scanning ion-selective electrode technique revealed that the solution near the localized corrosion region was alkalized. Scanning electron microscopy indicated that corrosion initiated around Fe-containing intermetallic particles, which serve as cathodic sites. It is hypothesized that during the processing of the Al/Si MMC, inter-diffusion causes Al atoms to diffuse into Si particles forming a layer of highly p-doped Si at the Al/Si interface. Thus, following the immersion of the MMC into the Na2SO4 solution, at the sites adjacent to the Fe-containing intermetallic particles where the Al matrix dissolved, highly p-doped Si surfaces were exposed to the solution. The highly p-doped surfaces can therefore serve as cathodic sites and exacerbate corrosion.