Corrosion resistance improvement of mild steel in different pH using peel garlic green inhibitor

Abstract

Corrosion resistance is the main drawback of mild steels, as AISI 1020. To decrease steel degradation, corrosion inhibitors are used and the green inhibitors gained relevance recently due to their low environment impact. Although extensively studied, the literature is mainly focused in the inhibitors use in acidic media. In this study, the aim was to investigate the efficiency of garlic peel as a green inhibitor in different aqueous solutions: acid (with HCl), neutral (with NaCl), and basic (with NaOH), in order to assess its inhibition capabilities across various pH levels. Mass loss and electrochemical corrosion tests demonstrated efficiency in all conditions tested. Additionally, SEM/EDS analysis was conducted to examine the reduction and alteration of corrosion products following the mass loss tests. In acidic media, the inhibitor's efficiency decreased with increasing exposure time, up to 24 h. Conversely, for neutral and basic media the inhibition efficiency increased up to 24 h. This increase was higher in the basic NaOH-containing solution. Quantum simulation further supported these findings, indicating that alliin and allicin, molecules found in garlic, generate more active specimens in basic conditions. This insight helps explain the superior performance observed in the NaOH solution.