Microstructure, Wetting Angle and Corrosion of Aluminum-silicon Alloys

Abstract

In this study the effect of composition, surface roughness and water droplet size on contact angle and corrosion properties of cast Aluminum-Silicon alloys containing Si from 5% to 50% have been examined. The water contact angle was measured on a given sample using a goniometer. In addition, the effect of surface roughness and droplet size on contact angle has been measured for alloys at a fixed composition. The microstructures can be found in this report with sizes of primary and eutectic Silicon as well as inter-particle spacing between Silicon. Contact angle measurements are accompanied with a photographic validation of the water droplet contact angles on the goniometer. For the samples inspected, the contact angle was observed to generally increase with roughness and droplet size. The contact angle decreases with weight percent Silicon for samples roughened with 240 grit and 800 grit sand paper. For fully polished samples, no clear trend was observed with weight percent Silicon. Lastly, the corrosion current was measured on all samples in both abraded state and fully polished state and these values were compared to comment on the change in resistance to corrosion with weight %Si and change in state of polish. No systematic variation in the corrosion potential or current was observed with weight percentage of Silicon (Si). However, a relative peak in corrosion resistance was observed for Al-22%Si for both abraded and polished samples.