ELECTROCHEMICAL BEHAVIOR AND CORROSION MORPHOLOGY OF SIC_P/5A06 ALUMINUM ALLOY COMPOSITE

The corrosion morphology and electrochemical behavior of 5A06 aluminum alloy and SiC_p/ 5A06 aluminum matrix composite (MMC), were investigated by means of the immersion test and various electrochemical techniques. The surface morphology of the samples tested was observed by optical (OM) and scanning electron microscopy (SEM) accompanied with energy dispersion spectroscopy (EDS) to reveal the damage caused by the immersion. It was found that the composite corroded faster than the matrix alloy due to the presence of fine and uniformly distributed intermetallics and crevices at the SiC_p/ matrix interface, rather than galvanic corrosion between SiC_p and the matrix phase. Cyclic potentiodynamic polarization (CV) and the variation of the open circuit potential with time (E_corr-t) were carried out and revealed similar corrosion potential (E_corr) and pitting potential (E_pit) for the composite and the matrix alloy. More pitting initiation sites were recorded on the composite surface, in accordance with its greater electronegative protection potential (E_prot).