Corrosion Behavior of Novel Al-Al₂O₃ Composites in Aerated 3.5% Chloride Solution

The corrosion behavior of novel Al-Al₂O₃ MMCs was evaluated in aerated 3.5% NaCl solution through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). These materials corrode almost spontaneously by pitting in aerated 3.5% NaCl solution. Observations indicate that intermetallic particles in these composites appear to play an important role in this pitting corrosion behavior. Addition of Al₂O₃ particles to the base alloys did not appear to increase their corrosion resistance significantly, although corrosion rate was affected by these reinforcement particles. In cyclic polarization experiments, the small difference between the pitting potentials and the repassivation potentials for these MMCs indicated their low resistance to pitting corrosion. EIS measurements indicate adsorption/diffusion phenomena at the interface of the composites. Electrically equivalent circuits are proposed to describe and substantiate the corrosion processes occurring in these materials.