This work involves studying the effect of adding SiO2 particles on corrosion behavior of Al-Cu-Mg alloy in 3.5% NaCl solution at room temperature using polarization method at scan rate 3 mV.sec-1.
According to potentiodynamic polarization test, the results of corrosion rate indicate that Al-Cu-Mg composites (1, 2, 3 wt% SiO2) gave decreasing in corrosion rate compared with Al-Cu-Mg alloy due to the covering the anodic sites for alloy by SiO2 particles and enhancing the passivity of surface and reducing the dissolution of aluminum. The cathodic Tafel slope (bc) were decreased after adding SiO2, while the anodic Tafel slopes (ba) were increased. It is inferred that the rate of change of current with change of potential was smaller during anodic polarization than that during cathodic polarization. Cyclic polarization measurements were carried out to estimate the pitting resistance of Al-Cu-Mg composites. The results show that a stable oxide film is formed during the forward scan on the surface of composites; also the hysteresis loop disappears, especially for composite with 3 wt%SiO2.