Abstract

Aluminum corrosion in acidic media leads to accelerated material degradation and significant economic losses. This study evaluated the aqueous extract of yerba mate (Ilex paraguariensis) as a green inhibitor for aluminum corrosion in 0.5 M HCl at temperatures (298–323 K) and extract concentrations (1%, 2.5%, and 5% v/v). The extract was characterized by FTIR, and its inhibitory performance was assessed using weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and contact angle analysis. Gravimetric results showed a decrease in corrosion rate with increasing extract concentration, reaching a maximum inhibition efficiency of 94% at 308 K and 5% v/v. The increase in activation energy in the presence of the inhibitor suggested the formation of an energy barrier associated with adsorption on the aluminum surface. Polarization studies indicated that the extract behaves as a mixed-type inhibitor, while EIS revealed an increase in charge transfer resistance and the formation of a protective adsorbed film. SEM images confirmed reduced corrosion damage, and contact angle measurements indicated increased surface hydrophobicity. The inhibition mechanism followed Langmuir adsorption behavior, suggesting adsorption of organic species at the aluminum–solution interface. These findings demonstrate that yerba mate extract is an effective corrosion inhibitor.

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