PROTECTIVE PROPERTIES OF PRETREATED 2024-T3 ALUMINUM

Aluminum (Al) and its alloys such as 2024-T3 is protected by passivating the metal surface via reinforcement of the aluminum oxide (Al oxide) layer on their surface. Electrochemical Impedance Spectroscopy (EIS) was employed to validate the protective property of pretreated 2024-T3. The Bode and Tafel plots were determined upon exposure to 5% NaCl at 0 h, 12 h and 24 h time intervals. Pretreated 2024 T3 was exposed to standard 5% NaCl to monitor the onset of corrosion. Corrosion is accompanied by a change in the substrate surface pH while galvanic dissolution upsets its passivation. The kinetics of pH change and dissolution of Al can be measured by a pH sensitive probe like fluorescein and Al3+ specific fluorescent probe (lumogallion), respectively. Raman spectroscopy was employed to determine the kinetics associated with the decay of the aluminum oxide barrier layer. Wetting and transport of exposed solution was determined by measuring the contact angle as a function of exposure time.