Electrochemical behavior of a discontinuously A6092/SiC/17.5p metal matrix composite in chloride containing solution

Aluminum alloys are used widely in automotive and aerospace industries. The demand for weight savings materials of superior mechanical, thermal and electrical properties has focused attention on aluminum metal matrix composites (AMMCs). AMMCs have been applied in areas that can cost-effectively capitalize on improvements in specific stiffness, specific strength, fatigue resistance, wear resistance, and coefficient of thermal expansion. However, AMMCs typically have lower damage tolerance properties than their unreinforced counterparts, and hence the extent of application in primary structures has been limited. In this paper, the corrosion resistance of ALCOA peak-aged Al6092/SiC/17.5p composite has been evaluated by recording of impedance spectra during immersion over one week in an air-exposed 3.5% NaCl. Results confirmed the occurrence of galvanic, crevice, intergranular corrosion and pitting attack due to the inhomogeneous structure of the composite which is the main reason behind enhancing the corrosion susceptibility. This paper formulates a complex hypothesis concerning the corrosion mechanisms of A6092/SiC/17.5p metal matrix composite in chloride containing solution as a function of time. A four-stage corrosion mechanism has been proposed to explain the sequence and the reasons of occurrence of each corrosion form.