An investigation into the impact of polyethylene glycol on guava leaf extract as a green corrosion inhibitor for mild steel in sulfuric acid

This study explores guava leaf extract (GLE) as a sustainable corrosion inhibitor for mild steel (M-St) in 2 M H₂SO₄ and assesses the synergistic effect of polyethylene glycol (PEG) as a co-additive. GLE effectively mitigated steel corrosion by forming an adsorbed protective film, with inhibition efficiency and surface coverage increasing with concentration (50 to 500 ppm) but decreasing at electrochemical impedance spectroscopy (EIS) elevated temperatures. The presence of PEG improved extract dispersion and adsorption, resulting in slightly higher efficiencies than GLE alone. At 500 ppm, inhibition efficiencies reached 84% for GLE and 85% for GLE–PEG. Adsorption behavior followed the Langmuir isotherm, while thermodynamic parameters confirmed an exothermic process involving chemisorption. Surface analyses revealed smoother, less corroded morphologies in inhibited samples, consistent with electrochemical findings. Overall, the results demonstrate that GLE, particularly when combined with PEG, offers an effective and eco-friendly approach for protecting M-St in acidic environments.