Investigation of the influence of SiC content and particle size variation on the corrosion resistance of Al-SiC matrix composite in neutral chloride solution

The effect of SiC content in 1070 aluminum at 10%, 15%, and 20% SiC contents in 1.75% neutral chloride solution was studied by potentiodynamic polarization and open circuit potential measurement. Results showed the aluminum composite at 10% SiC displayed the lowest corrosion rate. Increase in SiC content coupled with the electrochemical action of chloride anions increased the occurrence of localized corrosion as shown in the decrease of the passivation curve and morphological representations through optical microscopy analysis. Positive shifts in corrosion potential data with respect to SiC content show the dominant influence of anodic dissolution reactions. Further analysis of the effect of SiC particle size variation (3 mu m, 9 mu m, 29 mu m, and 45 mu m) on the corrosion resistance of the aluminum composite at 10% SiC showed the aluminum composite at with 3-mu m particle size had the lowest corrosion rate though all particle sizes studied showed extended passivation range. Cathodic potential shift was observed due to dominant reduction electrochemical reactions associated with localized corrosion and weakening of the passive film as the SiC particle size increases. It must be stated that increase in SiC particle size does not necessarily impaired the passive protective film of 1070AL/SiC matrix.