Electrochemical Impedance Study of an Al6063-12%SiC-Cr Composite Immersed in 3 wt. % Sodium Chloride

Aluminium Matrix Composites (AMCs) have received considerable attention among researchers and emerging as a prominent choice material for building and construction purposes. The preference of AMCs as replacement for conventional aluminium alloys is chiefly due to its excellent strength-to-weight ratio. However, the problem of accelerated corrosion attributed to the reinforcement particles used in the production of AMCs is well documented in the literature and serves as potential limitations for its applications. In this work, an attempt was made to study the influence of chromium (Cr) additions on the corrosion behaviour of Al6063-SiC-Cr composites. The novel Al6063-12%SiC-Cr composites were prepared with 0, 3 and 6 wt. % Cr by using a double stir casting technique. Electrochemical Impedance Spectroscopy (EIS) was used to study the corrosion behaviour of the as cast composites surfaces when immersed in 3 wt. % Sodium Chloride buffered to a pH of 8 ± 0.3 using 0.1 M Sodium Hydroxide (NaOH) solution for 72 hours. From the Nyquist plots and equivalent circuit fitting results, the charge transfer resistance values were observed to change from 10 to 3.7 KΩ, 30 to 9.5 KΩ, 19 to 2.8 KΩ for 0, 3 and 6 wt. % Cr content respectively after 72 hours of exposure. The increase in charge transfer resistance (Rct) values obtained with increasing Cr content was a clear indication of improved resistance to corrosion.