Corrosion Behavior of Aluminum Alloy in Chloride Media: Electrochemical and Surface Analysis

Abstract

The ziziphus spina-Christi extract (ZSC) was applied as a corrosion inhibitor for aluminum alloy 7051 (A7051) in an acidic medium, 0.1 M HCl. The potentiodynamic polarization measurement was employed to investigate the inhibitor's corrosion inhibition efficiency at various concentrations and different temperatures. The results showed a high inhibition efficiency, up to 95.84% at 7 ppm concentration at a lower examined temperature, indicating effective adsorption of the inhibitor molecule at the aluminium alloy surface.
The polarization data revealed that ZSC acts as a mixed-type corrosion inhibitor be effecting both cathodic reaction ( hydrogen evolution) and anodic reaction (metal dissolution). The influence of temperature was examined through Arrhenius and transition state approaches, showing that an increase in activation energy (Ea) occurred after adding ZSC. Adsorption behavior was examined using the Langmuir adsorption isotherm, and the calculated standard free energy of adsorption values confirmed a spontaneous adsorption process dominated by physical interactions.
The inhibition mechanism was attributed to the formation of a protective adsorbed film involving electrostatic interactions and donor–acceptor bonding between ZSC constituents and the A7051 surface. These findings suggest that Ziziphus spina-Christi leaves extract is an effective and environmentally friendly corrosion inhibitor for A7051 in acidic environments.