AN INVESTIGATION OF THE ELECTROCHEMICAL POLARIZATION BEHAVIOR OF 6061-ALUMINUM METAL-MATRIX COMPOSITES

Electrochemical polarisation measurements have been made on silicon ca rbide (SiC), 6061 aluminium metal-silicon carbide metal matrix composi te (MMC) and the similarly processed unreinforced alloy in aerated and de-aerated 3.5 wt% NaCl. The effect of the pH of de-aerated solutions was also evaluated and electrochemical polarisation measurements were made with alloys with different processing histories. Comparison of t he cathodic current densities on SiC and 6061 Al suggests that there i s no basis for significant galvanic interaction between the SiC and Al alloy in SiC/6061 Al. The distinct polarisation behaviour of SiC/6061 Al compared to 6061 Al is considered to be due to the increased area fraction of intermetallic particles and to differences in the characte ristics of the surface film of the MMC and the unreinforced alloy. The effects of SiC reinforcement on the electrochemistry of 6061 Al canno t be generalised and are specific functions of the environmental condi tions and the processing route.