ELECTROCHEMICAL-BEHAVIOR OF THE ALUMINUM ALLOY-2024 AND ALUMINUM ALLOY-7075 IN A SALINE SOLUTION

The electrochemical behaviour of aluminium alloys, 2024 in conditions T3 and T4 and also of 7075-T6, in 3% NaCl solution was studied. The corrosion and the pitting potentials were determined by potentiodynamic techniques. The potentiostatic method was also used to study the steady state at specific potentials. Among the three pH levels (1, 6 and 12), polarization studies showed active-passive behaviour only at pH 6. Thus, pitting potential was imposed at pH 6 for further corrosion behaviour. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), were used to characterize the surfaces of electrodes after they have been subjected to electrochemical testing. In the case of alloy 2024, image analysis permitted to relate the distribution and the size of the precipitates to different types of heat treatment (T3 and T4) and to the corrosion phenomena.